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I want a simple timeline component (like in video editing software) for a clojure/seesaw app and I am wondering if it is a good approach to implement this directly with clojure and seesaw or if I should write it in java and make my clojure wrapper around it.
Or more generally: is a functional programming language optimal for writing UI widgets? I cannot imagine doing that without a lot of state involved. And wasn't OO invented for UI-development in the first place?
You could go either way. On Overtone, we've built a number of custom graphical components directly in Clojure with Seesaw. Many times, an atom and (seesaw.core/canvas) is sufficient for this kind of thing.
Depending on how fancy you're going to get, one reason to do it in Clojure is you can extend Seesaw's protocols (selection, binding, etc) to the new widget so it works seamlessly with Seesaw. Another consideration is whether your widget needs to make use of Clojure data from other parts of the app. This will be much cleaner from Clojure than Java.
That said, if you're comfortable in Swing/Java, you can do it there and Seesaw will be perfectly happy to work with a custom widget built in Java. Good luck!
FP is good for doing UI programming but for that the underlying UI framework should also be based on FP concepts like FRP etc. In your case the underlying UI framework (Swing) is OO based and hence it would be more easy to implement it in Java but you can still do it in seesaw.
All else being equal (i.e. assuming you know both Clojure and Java), I would probably write this as a custom Swing component in Java.
Reasons:
Swing is fundamentally a Java-based OOP framework and is a better fit with Java in terms of paradigm
Mutable state is easier in Java than in Clojure
If you write it in Java, you can use it elsewhere more easily (e.g. as a library from other Java code)
It's easy to wrap a Swing component in Clojure after you have created it
Of course, for the application logic itself I would certainly prefer Clojure.
Why would it be better to use classes while programming in ASE than just using object oriented programming? Can you give me some good real world sittuations of when you should use classes? I'm asking this question because I want to better understand why I should use classes in flash apps I'm going to make and am making.
If you're just using AS code on frames, you're not using object oriented programming per-se, you're just running procedural scripts affecting objects.
The advantages for flash are the same for any other class-based OOP paradigm:
Separation of code into understandable hierarchy
"easy" code reuse
All design patterns that are associated with OOP
inheritance and extension
(for more just google "advantages of Object Oriented Programming")
I find that the advantages of OOP don't seem to make a difference during the first iteration. You're writing the same essential code either way. The advantage really comes out in the second or third similar project where you can start to reuse stuff that you made before, tweak a few parameters, extend a few classes, and have a different looking flash program without rewriting all the code.
If you make enough projects, eventually you'll find yourself with a library or framework of classes that you can easily reuse to make very powerful applications.
This question already has answers here:
What is the difference between a framework and a library? [closed]
(22 answers)
Closed 6 years ago.
What is the difference between a Framework, a Toolkit and a Library?
The most important difference, and in fact the defining difference between a library and a framework is Inversion of Control.
What does this mean? Well, it means that when you call a library, you are in control. But with a framework, the control is inverted: the framework calls you. (This is called the Hollywood Principle: Don't call Us, We'll call You.) This is pretty much the definition of a framework. If it doesn't have Inversion of Control, it's not a framework. (I'm looking at you, .NET!)
Basically, all the control flow is already in the framework, and there's just a bunch of predefined white spots that you can fill out with your code.
A library on the other hand is a collection of functionality that you can call.
I don't know if the term toolkit is really well defined. Just the word "kit" seems to suggest some kind of modularity, i.e. a set of independent libraries that you can pick and choose from. What, then, makes a toolkit different from just a bunch of independent libraries? Integration: if you just have a bunch of independent libraries, there is no guarantee that they will work well together, whereas the libraries in a toolkit have been designed to work well together – you just don't have to use all of them.
But that's really just my interpretation of the term. Unlike library and framework, which are well-defined, I don't think that there is a widely accepted definition of toolkit.
Martin Fowler discusses the difference between a library and a framework in his article on Inversion of Control:
Inversion of Control is a key part of
what makes a framework different to a
library. A library is essentially a
set of functions that you can call,
these days usually organized into
classes. Each call does some work and
returns control to the client.
A framework embodies some abstract
design, with more behavior built in.
In order to use it you need to insert
your behavior into various places in
the framework either by subclassing or
by plugging in your own classes. The
framework's code then calls your code
at these points.
To summarize: your code calls a library but a framework calls your code.
Diagram
If you are a more visual learner, here is a diagram that makes it clearer:
(Credits: http://tom.lokhorst.eu/2010/09/why-libraries-are-better-than-frameworks)
The answer provided by Barrass is probably the most complete. However, the explanation could easily be stated more clearly. Most people miss the fact that these are all nested concepts. So let me lay it out for you.
When writing code:
eventually you discover sections of code that you're repeating in your program, so you refactor those into Functions/Methods.
eventually, after having written a few programs, you find yourself copying functions you already made into new programs. To save yourself time you bundle those functions into Libraries.
eventually you find yourself creating the same kind of user interfaces every time you make use of certain libraries. So you refactor your work and create a Toolkit that allows you to create your UIs more easily from generic method calls.
eventually, you've written so many apps that use the same toolkits and libraries that you create a Framework that has a generic version of this boilerplate code already provided so all you need to do is design the look of the UI and handle the events that result from user interaction.
Generally speaking, this completely explains the differences between the terms.
Introduction
There are various terms relating to collections of related code, which have both historical (pre-1994/5 for the purposes of this answer) and current implications, and the reader should be aware of both, particularly when reading classic texts on computing/programming from the historic era.
Library
Both historically, and currently, a library is a collection of code relating to a specific task, or set of closely related tasks which operate at roughly the same level of abstraction. It generally lacks any purpose or intent of its own, and is intended to be used by (consumed) and integrated with client code to assist client code in executing its tasks.
Toolkit
Historically, a toolkit is a more focused library, with a defined and specific purpose. Currently, this term has fallen out of favour, and is used almost exclusively (to this author's knowledge) for graphical widgets, and GUI components in the current era. A toolkit will most often operate at a higher layer of abstraction than a library, and will often consume and use libraries itself. Unlike libraries, toolkit code will often be used to execute the task of the client code, such as building a window, resizing a window, etc. The lower levels of abstraction within a toolkit are either fixed, or can themselves be operated on by client code in a proscribed manner. (Think Window style, which can either be fixed, or which could be altered in advance by client code.)
Framework
Historically, a framework was a suite of inter-related libraries and modules which were separated into either 'General' or 'Specific' categories. General frameworks were intended to offer a comprehensive and integrated platform for building applications by offering general functionality, such as cross platform memory management, multi-threading abstractions, dynamic structures (and generic structures in general). Historical general frameworks (Without dependency injection, see below) have almost universally been superseded by polymorphic templated (parameterised) packaged language offerings in OO languages, such as the STL for C++, or in packaged libraries for non-OO languages (guaranteed Solaris C headers). General frameworks operated at differing layers of abstraction, but universally low level, and like libraries relied on the client code carrying out it's specific tasks with their assistance.
'Specific' frameworks were historically developed for single (but often sprawling) tasks, such as "Command and Control" systems for industrial systems, and early networking stacks, and operated at a high level of abstraction and like toolkits were used to carry out execution of the client codes tasks.
Currently, the definition of a framework has become more focused and taken on the "Inversion of Control" principle as mentioned elsewhere as a guiding principle, so program flow, as well as execution is carried out by the framework. Frameworks are still however targeted either towards a specific output; an application for a specific OS for example (MFC for MS Windows for example), or for more general purpose work (Spring framework for example).
SDK: "Software Development Kit"
An SDK is a collection of tools to assist the programmer to create and deploy code/content which is very specifically targeted to either run on a very particular platform or in a very particular manner. An SDK can consist of simply a set of libraries which must be used in a specific way only by the client code and which can be compiled as normal, up to a set of binary tools which create or adapt binary assets to produce its (the SDK's) output.
Engine
An Engine (In code collection terms) is a binary which will run bespoke content or process input data in some way. Game and Graphics engines are perhaps the most prevalent users of this term, and are almost universally used with an SDK to target the engine itself, such as the UDK (Unreal Development Kit) but other engines also exist, such as Search engines and RDBMS engines.
An engine will often, but not always, allow only a few of its internals to be accessible to its clients. Most often to either target a different architecture, change the presentation of the output of the engine, or for tuning purposes. Open Source Engines are by definition open to clients to change and alter as required, and some propriety engines are fixed completely. The most often used engines in the world however, are almost certainly JavaScript Engines. Embedded into every browser everywhere, there are a whole host of JavaScript engines which will take JavaScript as an input, process it, and then output to render.
API: "Application Programming Interface"
The final term I am answering is a personal bugbear of mine: API, was historically used to describe the external interface of an application or environment which, itself was capable of running independently, or at least of carrying out its tasks without any necessary client intervention after initial execution. Applications such as Databases, Word Processors and Windows systems would expose a fixed set of internal hooks or objects to the external interface which a client could then call/modify/use, etc to carry out capabilities which the original application could carry out. API's varied between how much functionality was available through the API, and also, how much of the core application was (re)used by the client code. (For example, a word processing API may require the full application to be background loaded when each instance of the client code runs, or perhaps just one of its linked libraries; whereas a running windowing system would create internal objects to be managed by itself and pass back handles to the client code to be utilised instead.
Currently, the term API has a much broader range, and is often used to describe almost every other term within this answer. Indeed, the most common definition applied to this term is that an API offers up a contracted external interface to another piece of software (Client code to the API). In practice this means that an API is language dependent, and has a concrete implementation which is provided by one of the above code collections, such as a library, toolkit, or framework.
To look at a specific area, protocols, for example, an API is different to a protocol which is a more generic term representing a set of rules, however an individual implementation of a specific protocol/protocol suite that exposes an external interface to other software would most often be called an API.
Remark
As noted above, historic and current definitions of the above terms have shifted, and this can be seen to be down to advances in scientific understanding of the underlying computing principles and paradigms, and also down to the emergence of particular patterns of software. In particular, the GUI and Windowing systems of the early nineties helped to define many of these terms, but since the effective hybridisation of OS Kernel and Windowing system for mass consumer operating systems (bar perhaps Linux), and the mass adoption of dependency injection/inversion of control as a mechanism to consume libraries and frameworks, these terms have had to change their respective meanings.
P.S. (A year later)
After thinking carefully about this subject for over a year I reject the IoC principle as the defining difference between a framework and a library. There ARE a large number of popular authors who say that it is, but there are an almost equal number of people who say that it isn't. There are simply too many 'Frameworks' out there which DO NOT use IoC to say that it is the defining principle. A search for embedded or micro controller frameworks reveals a whole plethora which do NOT use IoC and I now believe that the .NET language and CLR is an acceptable descendant of the "general" framework. To say that IoC is the defining characteristic is simply too rigid for me to accept I'm afraid, and rejects out of hand anything putting itself forward as a framework which matches the historical representation as mentioned above.
For details of non-IoC frameworks, see, as mentioned above, many embedded and micro frameworks, as well as any historical framework in a language that does not provide callback through the language (OK. Callbacks can be hacked for any device with a modern register system, but not by the average programmer), and obviously, the .NET framework.
A library is simply a collection of methods/functions wrapped up into a package that can be imported into a code project and re-used.
A framework is a robust library or collection of libraries that provides a "foundation" for your code. A framework follows the Inversion of Control pattern. For example, the .NET framework is a large collection of cohesive libraries in which you build your application on top of. You can argue there isn't a big difference between a framework and a library, but when people say "framework" it typically implies a larger, more robust suite of libraries which will play an integral part of an application.
I think of a toolkit the same way I think of an SDK. It comes with documentation, examples, libraries, wrappers, etc. Again, you can say this is the same as a framework and you would probably be right to do so.
They can almost all be used interchangeably.
very, very similar, a framework is usually a bit more developed and complete then a library, and a toolkit can simply be a collection of similar librarys and frameworks.
a really good question that is maybe even the slightest bit subjective in nature, but I believe that is about the best answer I could give.
Library
I think it's unanimous that a library is code already coded that you can use so as not to have to code it again. The code must be organized in a way that allows you to look up the functionality you want and use it from your own code.
Most programming languages come with standard libraries, especially some code that implements some kind of collection. This is always for the convenience that you don't have to code these things yourself. Similarly, most programming languages have construct to allow you to look up functionality from libraries, with things like dynamic linking, namespaces, etc.
So code that finds itself often needed to be re-used is great code to be put inside a library.
Toolkit
A set of tools used for a particular purpose. This is unanimous. The question is, what is considered a tool and what isn't. I'd say there's no fixed definition, it depends on the context of the thing calling itself a toolkit. Example of tools could be libraries, widgets, scripts, programs, editors, documentation, servers, debuggers, etc.
Another thing to note is the "particular purpose". This is always true, but the scope of the purpose can easily change based on who made the toolkit. So it can easily be a programmer's toolkit, or it can be a string parsing toolkit. One is so broad, it could have tool touching everything programming related, while the other is more precise.
SDKs are generally toolkits, in that they try and bundle a set of tools (often of multiple kind) into a single package.
I think the common thread is that a tool does something for you, either completely, or it helps you do it. And a toolkit is simply a set of tools which all perform or help you perform a particular set of activities.
Framework
Frameworks aren't quite as unanimously defined. It seems to be a bit of a blanket term for anything that can frame your code. Which would mean: any structure that underlies or supports your code.
This implies that you build your code against a framework, whereas you build a library against your code.
But, it seems that sometimes the word framework is used in the same sense as toolkit or even library. The .Net Framework is mostly a toolkit, because it's composed of the FCL which is a library, and the CLR, which is a virtual machine. So you would consider it a toolkit to C# development on Windows. Mono being a toolkit for C# development on Linux. Yet they called it a framework. It makes sense to think of it this way too, since it kinds of frame your code, but a frame should more support and hold things together, then do any kind of work, so my opinion is this is not the way you should use the word.
And I think the industry is trying to move into having framework mean an already written program with missing pieces that you must provide or customize. Which I think is a good thing, since toolkit and library are great precise terms for other usages of "framework".
Framework: installed on you machine and allowing you to interact with it. without the framework you can't send programming commands to your machine
Library: aims to solve a certain problem (or several problems related to the same category)
Toolkit: a collection of many pieces of code that can solve multiple problems on multiple issues (just like a toolbox)
It's a little bit subjective I think. The toolkit is the easiest. It's just a bunch of methods, classes that can be use.
The library vs the framework question I make difference by the way to use them. I read somewhere the perfect answer a long time ago. The framework calls your code, but on the other hand your code calls the library.
In relation with the correct answer from Mittag:
a simple example. Let's say you implement the ISerializable interface (.Net) in one of your classes. You make use of the framework qualities of .Net then, rather than it's library qualities. You fill in the "white spots" (as mittag said) and you have the skeleton completed. You must know in advance how the framework is going to "react" with your code. Actually .net IS a framework, and here is where i disagree with the view of Mittag.
The full, complete answer to your question is given very lucidly in Chapter 19 (the whole chapter devoted to just this theme) of this book, which is a very good book by the way (not at all "just for Smalltalk").
Others have noted that .net may be both a framework and a library and a toolkit depending on which part you use but perhaps an example helps. Entity Framework for dealing with databases is a part of .net that does use the inversion of control pattern. You let it know your models it figures out what to do with them. As a programmer it requires you to understand "the mind of the framework", or more realistically the mind of the designer and what they are going to do with your inputs. datareader and related calls, on the other hand, are simply a tool to go get or put data to and from table/view and make it available to you. It would never understand how to take a parent child relationship and translate it from object to relational, you'd use multiple tools to do that. But you would have much more control on how that data was stored, when, transactions, etc.
I just started creating my data-access layer using LinqToSql. Everybody is talking about the cool syntax and I really like Linq in general.
But when I saw how your classes get generated if you drag some tables on the LinqContext I was amazed: So much code which nobody would need?!
So I looked how other people used LinqToSql, for example Rob Connery at his StoreFront Demo.
As I don't like the way that all this code is generated I created my domain layer by hand and used the generated classes as reference. With that solution I'm fine, as I can use the features provided by Linq (dereferred execution, lazy loading, ...) and my domain layer is quite easy to understand.
How are you using LinqToSql?
The created classes are not as heavy as it seems. Of course it takes quite a few lines of code, but all in all it is as lightweight as it can be for the features it's providing.
I used to create my own tables, too, but now instead I just use the LINQtoSQL DataContext. Why? Creating is simpler, the features are better, interoperability works, it is probably even faster than my own stuff (not in every aspect. Usually my own stuff was extremely fast in one thing, but the generic stuff was faster in everything else).
But the most important part: it is easier to bring new developers into the LINQ stuff than into my own. There are tutorials, example codes, documentation, everything, which I'd have to create for my code by myself. Same with using my stuff with other technology, like WCF or data binding. There are a lot of pitfalls to be taken care of.
I learned not to develop myself into a corner the hard way, it looks fast and easy at the start, is a lot more fun than learning how to use the libs, but is a real pain in the a after a few months down the road, usually even for myself.
After some time the novelty of creating my own data containers wears off, and I noticed the pain connected to adding a feature. A feature I would have had for free, if I had used the provided classes.
Next thing I had to explain my code to some other programmer. Had I used the provided classes, I could have pointed him to some web site to learn about the stuff. But for my classes, I had to train him himself, which took a long time and made it hard to get new people on a project.
LinqToSql generates a set of partial classes for your tables. You can add interface definitions to the 'other half' of these partial classes that implement your domain model.
Then, if you use the repository pattern to wrap access to the Linq queries, so that they return interface implementations of your objects (the underlying Linq objects), LinqToSql becomes quite flexible.
You can hand-write your own classes and either use the LINQ to SQL attributes to declare the mappings or an external XML file.
If you would like to stick with the existing designer and just modify the code generation process pick up my templates that let you tailor the generated code.
Use compiled queries. Linq to SQL is dog slow otherwise. Really.
We use our hand crafted domain model, along with the generated classes, plus a simple utility which utilizes reflection to convert between them when needed. We've contemplated writing a converter generator if we reach a point where reflection creates a performance bottleneck.
Since debate without meaningful terms is meaningless, I figured I would point at the elephant in the room and ask: What exactly makes a language "object-oriented"? I'm not looking for a textbook answer here, but one based on your experiences with OO languages that work well in your domain, whatever it may be.
A related question that might help to answer first is: What is the archetype of object-oriented languages and why?
Definitions for Object-Orientation are of course a huge can of worms, but here are my 2 cents:
To me, Object-Orientation is all about objects that collaborate by sending messages. That is, to me, the single most important trait of an object-oriented language.
If I had to put up an ordered list of all the features that an object-oriented language must have, it would look like this:
Objects sending messages to other objects
Everything is an Object
Late Binding
Subtype Polymorphism
Inheritance or something similarly expressive, like Delegation
Encapsulation
Information Hiding
Abstraction
Obviously, this list is very controversial, since it excludes a great variety of languages that are widely regarded as object-oriented, such as Java, C# and C++, all of which violate points 1, 2 and 3. However, there is no doubt that those languages allow for object-oriented programming (but so does C) and even facilitate it (which C doesn't). So, I have come to call languages that satisfy those requirements "purely object-oriented".
As archetypical object-oriented languages I would name Self and Newspeak.
Both satisfy the above-mentioned requirements. Both are inspired by and successors to Smalltalk, and both actually manage to be "more OO" in some sense. The things that I like about Self and Newspeak are that both take the message sending paradigm to the extreme (Newspeak even more so than Self).
In Newspeak, everything is a message send. There are no instance variables, no fields, no attributes, no constants, no class names. They are all emulated by using getters and setters.
In Self, there are no classes, only objects. This emphasizes, what OO is really about: objects, not classes.
According to Booch, the following elements:
Major:
Abstraction
Encapsulation
Modularity
Hierarchy (Inheritance)
Minor:
Typing
Concurrency
Persistence
Basically Object Oriented really boils down to "message passing"
In a procedural language, I call a function like this :
f(x)
And the name f is probably bound to a particular block of code at compile time. (Unless this is a procedural language with higher order functions or pointers to functions, but lets ignore that possibility for a second.) So this line of code can only mean one unambiguous thing.
In an object oriented language I pass a message to an object, perhaps like this :
o.m(x)
In this case. m is not the name of a block of code, but a "method selector" and which block of code gets called actually depends on the object o in some way. This line of code is more ambiguous or general because it can mean different things in different situations, depending on o.
In the majority of OO languages, the object o has a "class", and the class determines which block of code is called. In a couple of OO languages (most famously, Javascript) o doesn't have a class, but has methods directly attached to it at runtime, or has inherited them from a prototype.
My demarcation is that neither classes nor inheritance are necessary for a language to be OO. But this polymorphic handling of messages is essential.
Although you can fake this with function pointers in say C, that's not sufficient for C to be called an OO language, because you're going to have to implement your own infrastructure. You can do that, and a OO style is possible, but the language hasn't given it to you.
It's not really the languages that are OO, it's the code.
It is possible to write object-oriented C code (with structs and even function pointer members, if you wish) and I have seen some pretty good examples of it. (Quake 2/3 SDK comes to mind.) It is also definitely possible to write procedural (i.e. non-OO) code in C++.
Given that, I'd say it's the language's support for writing good OO code that makes it an "Object Oriented Language." I would never bother with using function pointer members in structs in C, for example, for what would be ordinary member functions; therefore I will say that C is not an OO language.
(Expanding on this, one could say that Python is not object oriented, either, with the mandatory "self" reference on every step and constructors called init, whatnot; but that's a Religious Discussion.)
Smalltalk is usually considered the archetypal OO language, although Simula is often cited as the first OO language.
Current OO languages can be loosely categorized by which language they borrow the most concepts from:
Smalltalk-like: Ruby, Objective-C
Simula-like: C++, Object Pascal, Java, C#
I am happy to share this with you guys, it was quite interesting and helpful to me. This is an extract from a 1994 Rolling Stone interview where Steve (not a programmer) explains OOP in simple terms.
Jeff Goodell: Would you explain, in simple terms, exactly what object-oriented software is?
Steve Jobs: Objects are like people. They’re living, breathing things that have knowledge inside them about how to do things and have memory inside them so they can remember things. And rather than interacting with them at a very low level, you interact with them at a very high level of abstraction, like we’re doing right here.
Here’s an example: If I’m your laundry object, you can give me your dirty clothes and send me a message that says, “Can you get my clothes laundered, please.” I happen to know where the best laundry place in San Francisco is. And I speak English, and I have dollars in my pockets. So I go out and hail a taxicab and tell the driver to take me to this place in San Francisco. I go get your clothes laundered, I jump back in the cab, I get back here. I give you your clean clothes and say, “Here are your clean clothes.”
You have no idea how I did that. You have no knowledge of the laundry place. Maybe you speak French, and you can’t even hail a taxi. You can’t pay for one, you don’t have dollars in your pocket. Yet, I knew how to do all of that. And you didn’t have to know any of it. All that complexity was hidden inside of me, and we were able to interact at a very high level of abstraction. That’s what objects are. They encapsulate complexity, and the interfaces to that complexity are high level.
As far as I can tell, the main view of what makes a language "Object Oriented" is supporting the idea of grouping data, and methods that work on that data, which is generally achieved through classes, modules, inheritance, polymorphism, etc.
See this discussion for an overview of what people think (thought?) Object-Orientation means.
As for the "archetypal" OO language - that is indeed Smalltalk, as Kristopher pointed out.
Supports classes, methods, attributes, encapsulation, data hiding, inheritance, polymorphism, abstraction...?
Disregarding the theoretical implications, it seems to be
"Any language that has a keyword called 'class'" :-P
To further what aib said, I would say that a language isn't really object oriented unless the standard libraries that are available are object oriented. The biggest example of this is PHP. Although it supports all the standard object oriented concepts, the fact that such a large percentage of the standard libraries aren't object oriented means that it's almost impossible to write your code in an object oriented way.
It doesn't matter that they are introducing namespaces if all the standard libraries still require you to prefix all your function calls with stuff like mysql_ and pgsql_, when in a language that supported namespaces in the actual API, you could get rid of functions with mysql_ and have just a simple "include system.db.mysql.*" at the top of your file so that it would know where those things came from.
when you can make classes, it is object-oriented
for example : java is object-oriented, javascript is not, and c++ looks like some kind of "object-curious" language
In my experience, languages are not object-oriented, code is.
A few years ago I was writing a suite of programs in AppleScript, which doesn't really enforce any object-oriented features, when I started to grok OO. It's clumsy to write Objects in AppleScript, although it is possible to create classes, constructors, and so forth if you take the time to figure out how.
The language was the correct language for the domain: getting different programs on the Macintosh to work together to accomplish some automatic tasks based on input files. Taking the trouble to self-enforce an object-oriented style was the correct programming choice because it resulted in code that was easier to trouble-shoot, test, and understand.
The feature that I noticed the most in changing that code over from procedural to OO was encapsulation: both of properties and method calls.
Simples:(compare insurance character)
1-Polymorphism
2-Inheritance
3-Encapsulation
4-Re-use.
:)
Object: An object is a repository of data. For example, if MyList is a ShoppingList object, MyList might record your shopping list.
Class: A class is a type of object. Many objects of the same class might exist; for instance, MyList and YourList may both be ShoppingList objects.
Method: A procedure or function that operates on an object or a class. A method is associated with a particular class. For instance, addItem might be a method that adds an item to any ShoppingList object. Sometimes a method is associated with a family of classes. For instance, addItem might operate on any List, of which a ShoppingList is just one type.
Inheritance: A class may inherit properties from a more general class. For example, the ShoppingList class inherits from the List class the property of storing a sequence of items.
Polymorphism: The ability to have one method call work on several different classes of objects, even if those classes need different implementations of the method call. For example, one line of code might be able to call the "addItem" method on every kind of List, even though adding an item to a ShoppingList is completely different from adding an item to a ShoppingCart.
Object-Oriented: Each object knows its own class and which methods manipulate objects in that class. Each ShoppingList and each ShoppingCart knows which implementation of addItem applies to it.
In this list, the one thing that truly distinguishes object-oriented languages from procedural languages (C, Fortran, Basic, Pascal) is polymorphism.
Source: https://www.youtube.com/watch?v=mFPmKGIrQs4&list=PL-XXv-cvA_iAlnI-BQr9hjqADPBtujFJd
If a language is designed with the facilities specifically to support object-oriented programming(4 features) then it is an Object-oriented programming language.
You can program in an object-orientated style in more or less any language.It’s the code that is object-oriented not the language.
Examples of real object-oriented languages are Java, c#, Python, Ruby, C++.
Also, it's possible to have extensions to provide Object-Oriented features like PHP, Perl etc.
You can write an object-oriented code with C but it is not object-oriented prog. lang. It is not designed for that (that was the whole point of c++)
Archetype
The ability to express real-world scenarios in code.
foreach(House house in location.Houses)
{
foreach(Deliverable mail in new Mailbag(new Deliverable[]
{
GetLetters(),
GetPackages(),
GetAdvertisingJunk()
})
{
if(mail.AddressedTo(house))
{
house.Deliver(mail);
}
}
}
-
foreach(Deliverable myMail in GetMail())
{
IReadable readable = myMail as IReadable;
if ( readable != null )
{
Console.WriteLine(readable.Text);
}
}
Why?
To help us understand this more easily. It makes better sense in our heads and if implemented correctly makes the code more efficient, re-usable and reduces repetition.
To achieve this you need:
Pointers/References to ensure that this == this and this != that.
Classes to point to (e.g. Arm) that store data (int hairyness) and operations (Throw(IThrowable))
Polymorphism (Inheritance and/or Interfaces) to treat specific objects in a generic fashion so you can read books as well as graffiti on the wall (both implement IReadable)
Encapsulation because an apple doesn't expose an Atoms[] property