My good friend, Wikipedia, didn't give me a very good response to that question. So:
What are language bindings?
How do they work?
Specifically accessing functions from code written in language X of a library written in language Y.
Let's say you create a C library to post stuff to stackoverflow. Now you want to be able to use the same library from Python. In this case, you will write Python bindings for your library.
Also see SWIG: http://www.swig.org
In the context of code libraries, bindings are wrapper libraries that bridge between two programming languages so that a library that was written for one language can also be implicitly used in another language.
For example, libsvn is the API for Subversion and was written in C. If you want to access Subversion from within Java code you can use libsvn-java. libsvn-java depends on libsvn being installed because libsvn-java is a mere bridge between the Java programming language and libsvn, providing an API that merely calls functions of libsvn to do the real work.
Okay, now the question has been clarified, this isn't really relevant so I'm moving it to a new question
Binding generally refers to a mapping of one thing to another - i.e. a datasource to a presentation object. It can typically refer to binding data from a database, or similar source (XML file, web service etc) to a presentation control or element - think list or table in HTML, combo box or data grid in desktop software.
...If that's the kind of binding you're interested in, read on...
You generally have to bind the presentation element to the datasource, not the other way around. This would involve some kind of mapping - i.e. which fields from the datasource do you want to appear in the output.
For more information in a couple of environments see:
Data binding in .Net using Windows Forms
http://www.codeproject.com/KB/database/databindingconcepts.aspx
http://www.akadia.com/services/dotnet_databinding.html
ASP.NET data binding
http://support.microsoft.com/kb/307860
http://www.15seconds.com/issue/040630.htm
http://www.w3schools.com/ASPNET/aspnet_databinding.asp
Java data binding
http://www.xml.com/pub/a/2003/09/03/binding.html
Python data binding
http://www.xml.com/pub/a/2005/07/27/py-xml.html
General XML data binding
http://www.rpbourret.com/xml/XMLDataBinding.htm
In Flex (Actionscript 3). Source
A data binding copies the value of a property in one object to a property in another object. You can bind the properties of following objects: Flex components, Flex data models, and Flex data services.
The object property that provides the data is known as the source property. The object property that receives the data is known as the destination property.
The following example binds the text property of a TextInput component (the source property) to the text property of a Label component (the destination property) so that text entered in the TextInput component is displayed by the Label component:
<mx:TextInput id="LNameInput"></mx:TextInput>
...
<mx:Label text="{LNameInput.text}"></mx:Label>
Data binding is usually a simple way to bind a model to user interface components. For example, you have a class with a FirstName property. In flex you could easily bind that property to a textbox by setting the value of the textbox to {Object.FirstName}. Then, every time that FirstName property changes, the textbox will be updated without requiring you to write any code to monitor that property for changes.
Hope that helps.
Matt
Related
I created an object that is backed by a Foundry Form and I would like to provide a user to change the properties of that object. I linked the form to the object and created a title property that is a hidden/ derived value in the object creation form. A user can edit property a and property b and the title of the object will be ab.
When the user updates the object in the edit form the title does not update. Is there a configuration I need to change?
Yes, this is possible. There's actually two ways to achieve this, I'll list them in order of my preference:
Using an action
The modern way of achieving this is to use an action. Actions allow you to flexibly "intercept" events like writes from users and do extra actions (hence the name) or prevent things from happening. They are a fairly new feature in foundry.
The basic concept is that you write a little piece of code (a function on an object) that gets executed when the object is modified. The function can then modify the object further or prevent the modification.
This is very flexible, because it will allow you to automatically update the title of the object regardless of how and when the object was edited. You can also apply more complex logic to derive the title from e.g. multiple properties with fallbacks, or modify a property in a certain way before you put it into the title, et cetera.
The drawback is that this requires you to write some code.
On your stack, if you navigate to https://www.palantir.com/docs/foundry/functions/use-functions/#actions you will find an introduction on how to get started with actions. The example solves the exact use-case you're asking for.
Using form templates
Another approach that's simpler and does not require writing any code, but is much less flexible, is to use a template in the form. You can create a template form widget that's invisible, and is automatically populated by values from other form fields.
The advantage is that this is very easy and quick to set up, but the disadvantage is that it will only apply when the object is edited through the form, and you can really only do concatenation, not much else.
It sounds like this is what you attempted to do, and I believe this should work. If it doesn't, I would check the following things:
make the template visible to see that it gets filled out like you expect it to
make sure the template is set to store its response into the right property on the object
make sure the user is using the form to edit the object, not some other way (like editing the property directly in hubble)
I have 2 different types components. They both only use and contain an HTML5-canvas element, but need to show different types of data on a chart:
Component A (Only ever 1 of these)
Component B (0 to 4 of these)
Both components need the dateTime of the first data-entry from the two data-sets, but the dateTime of the last entry comes from their own respective data-sets.
Component A needs its first entry date from Component B.
Currently I do it like this:
Component B has the method that finds the date-limits from its own dataset. Using an Observer-pattern & Subjects, I broadcasts the returned dates through a service and into Component A.
The problem with this though, is that coupling suddenly becomes pretty tight. I can't initialize component A first, because it needs B to do its calculation first. Both components ideally should initialize and show/share their data simultaneously, and continue to do so. (E.g. If a user scrolls in one chart it should scroll all other components too, and so on.)
This is why I wanted an extra layer added on top of these components. A controller if you will.
I can't figure out what's best though:
A shared service that can take external data as input?
A container component? (Transclusion)
Another component, Component C, that A & B are children of?
As I'm still new to Angular 2, it's hard to tell which approach is best for future maintenance/development?
I'm being drawn towards creating another normal component as a parent, and have this component send and receive data to/from its children (A & B) as necessary.
I'm also uncertain as to what's "best practice" and if you can just use a component like an empty 'logic shell'. I've tried reading here and there, and I've found a lot, but I can't seem to get an exact answer to my question. It'll take time before I can comprehend all this knowledge and answer it myself, so I'm hoping someone could give me a helping nudge, thanks.
PS: I should add that my angular application will be a child-component in larger application, and will get its data from some other parent comp.
Why don't you put your logic into services?
You can also set up service hierarchies by injecting sub-services into a parent service.
If your logic is not UI / interaction related, you should put it into reusable services. If your logic is UI related, you could set up a parent component acting as a mediator between A and B (acting on their respective input/output parameters)
Whatever you do, it is a good idea to keep concerns separate.
Both A and B should not need to care about other components needing their output. Angular has Input/Output parameters for that.
Don't put some generic datetime calculation stuff into components. Make it reusable through services.
Keep coupling loose by introducing interfaces and injections.
Update:
Services should only use injectable constructor parameters, so you should pass your input using methods (or setters, but that is less expressive).
To pass arbitrary JSON objects, you could utilize any parameters. However if your json follows a certain structure, you could define an interface.
public doStuff(input: any): any { }
or
interface IMyDataContract {
dateField: string;
}
public doStuff(input: IMyDataContract): any { }
In my Windows Phone App there's a simple hierarchical model consisting of a class containing a collection of other domain objects.
In my xaml i have declared an ItemsContainer control that renders the items in the above mentioned collection as simple rectangles.
Now, at the VM level i have a structure that resembles my model with a parent VM having a collection of children VMs. Each child-VM encapsulates its own model.
Whenever the user taps the view bound to a child-VM a method of the parent-model object should be invoked taking the relevant child-model as parameter. This will in turn change some internal state that will be reflected (possibly) on all the child-views (not just the tapped one).
SO... given that i'm using the MVVM Light framework my current implementation is as follows:
Child-VM exposes a command
The command Execute method will use the messenger to notify the parent-VM of the tap event. The message (GenericMessage class) content will be the domain object encapsulated by the VM
The parent-VM executes the method of the parent-model using the message content as parameter
If the operation succeeds the parent-VM sends a new message to inform child-VMs of this fact. Once again the message content is the model object used as parameter in the method that was just invoked
Child-VMs raise a couple of PropertyChanged events that, finally, will update the bound views
It works but i fill it's a bit cumbersome. The thing that bugs me the most is the fact that when a child-view is tapped the associated VM will broadcast its encapsulated model object. Do you feel that there would be a better way of implementing such a system?
Thanks in advance for your precious help
Could you not just put the command on the parent viewmodel and pass the child viewmodel as the command parameter?
The parent view model can then just call methods on the child viewmodels to update them. I'm not sure I see the need for all these messages?
I am looking for some help with designing some functionality in my application. I already have something similar designed but this problem is a little different.
Background:
In my application we have different Modules. Data in each module can be associated to other modules. Each Module is represented by an Object in our application.
Module 1 can be associated with Module 2 and Module 3. Currently I use a factory to provide the proper DAO for getting and saving this data.
It looks something like this:
class Module1Factory {
public static Module1BridgeDAO createModule1BridgeDAO(int moduleid) {
switch (moduleId)
{
case Module.Module2Id: return new Module1_Module2DAO();
case Module.Module3Id: return new Module1_Module3DAO();
default: return null;
}
}
}
Module1_Module2 and Module1_Module3 implement the same BridgeModule interface. In the database I have a Table for every module (Module1, Module2, Module3). I also have a bridge table for each module (they are many to many) Module1_Module2, Module1_Module3 etc.
The DAO basically handles all code needed to manage the association and retrieve its own instance data for the calling module. Now when we add new modules that associate with Module1 we simply implement the ModuleBridge interface and provide the common functionality.
New Development
We are adding a new module that will have the ability to be associated with other Modules as well as specific properties of that module. The module is basically providing the user the ability to add their custom forms to our other modules. That way they can collect additional information along with what we provide.
I want to start associating my Form module with other modules and their properties. Ie if Module1 has a property Category, I want to associate an instance From data with that property.
There are many Forms. If a users creates an instance of Module2, they may always want to also have certain form(s) attached to that Module2 instance. If they create an instance of Module2 and select Category 1, then I may want additional Form(s) created.
I prototyped something like this:
Form
FormLayout (contains the labels and gui controls)
FormModule (associates a form with all instances of a module)
Form Instance (create an instance of a form to be filled out)
As I thought about it I was thinking about making a new FormModule table/class/dao for each Module and Property that I add. So I might have:
FormModule1
FormModule1Property1
FormModule1Property2
FormModule1Property3
FormModule1Property4
FormModule2
FormModule3
FormModule3Property1
Then as I did previously, I would use a factory to get the proper DAO for dealing with all of these. I would hand it an array of ids representing different modules and properties and it would return all of the DAOs that I need to call getForms(). Which in turn would return all of the forms for that particular bridge.
Some points
This will be for a new module so I dont need to expand on the factory code I provided. I just wanted to show an example of what I have done in the past.
The new module can be associated with: Other Modules (ie globally for any instance of that module data), Other module properties (ie only if the Module instance has a certian value in one of its properties)
I want to make it easy for developers to add associations with other modules and properties easily
Can any one suggest any design patterns or strategy's for achieving this?
If anything is unclear please let me know.
Thank you,
Al
You can use springs Dependency Injection feature. This would help you achieve the flexibility of instantiating the objects using an xml configuration file.
So, my suggestion would be go with the Springs.
I have a tree control in my GUI (with naturally lots of GUI/platform specific functions to handle the nodes).
I have a data model with its own complex set of nodes, children, properties etc..
I want the tree to display a representation of the model, be able to send messages to the nodes inside the model and be told to redraw itself when the model changes.
But I don't want the GUI code to need to know the details of the model's data types and I don't want to pollute the model by linking it to the GUI classes.
I can't get my head around how the controller is supposed to do this and what functions it should provide?
(this is in C++ but that shouldn't matter)
GUI "controls" don't quite fit neatly into a model-view-controller pattern because they typically have their own internal model rather than accepting a reference to one. If the control is structured that way, you'll need an adapter class that "data-binds" the control's internal model to the underlying data model.
This can accomplish something similar to what model-view-controller would, except that the adapter class plays the role both of a view hookup component (updating the GUI from the data model) and a controller (interpreting GUI events into model actions).
Qt provides a group of classes for model-view programming. You can hook a tree view to a filesystem model, for example, and neither directly know anything about each other (except a pointer to the model in the view).
Your requirements are:
Tree displays representation of model
Nodes in tree can send messages to nodes inside model
Tree redraws itself based on model changes
I don't know exactly what kind of data you're working with here, but a hierarchical model is a fairly simple thing. I'll take it as a given you know how to iterate hierarchical data and populate a tree view.
Your controller should have member function(s) for sending messages to the model. The parameters should be a model element and the message you want to send. This way, the UI is completely unaware of how the message gets to the element, but can get the messages through.
The last requirement is more tricky, and depends on a few things (e.g., the lifetime of the controller, application architecture, etc.) I'm going to assume the controller lives as long as the tree view does. If that's the case, then your controller should provide a way to set a callback on model changes. Then, when the controller changes the model, it can callback to the UI without being aware of the UI.
i think your troubles start with an unfortunate choice of words. the 'control' thingies doesn't have anything to do with the 'controller' in MVC. that's why some GUI libraries use other names (widgets is a common one).
your 'tree control' is the view, not the controller. it should be tied to the GUI, both for display, and to get GUI events and turn them into 'tree events'.
the controller gets those 'tree events' and does the necessary modifications to the model. that's where you couple the 'action' with the 'response'.
First Solution: You can implement a "Subject observer" pattern between model and view, with model as the subject and view as the observer. Whenever there is a change in the state of model, it can fire a event to all the observers those are registered, they can update themselves.
Second Solution: Introduce a controller, which registers with model as observer. Upon receiving a event for update from Model, it can update the view. Even you can decouple view from controller using one more subject observer pattern between controller and view
Third Solution: Use MVP pattern. Model view Presenter. This pattern used whenever there is no much computation in controller i.e., job of the controller is just to update its corresponding view. Here controller becomes Presenter.
You need a controller that sits outside the display widget but has the state of the tree (in MFc there are CTreeView/CTreeCtrl classes - there is a similiar separation in Qt) the tree controller handles all the data storage and calls redraws on the tree widget.
Changes in the tree widget get sent to the tree controller - so this controller needs to know about the gui functions.
The model will need set/get functions for all the relevant parameters for the nodes. But these can return simple types so aren't dependent on the gui.
Updating the view form the model requires sending a message, if you don't want the model to know about your gui messaging the best you can do is register a callback function (a void pointer to a function) from the tree controller - and call this to do an update.
This update function can then query the model for the changes.