I get a little bit confused by the tutorial at this site:
http://williammora.com/a-running-game-with-libgdx-part-2/
Why is it possible to give a body to the addActor method?
Can someone explain me this?
I thought I must give it some Actor.
private void setUpGround() {
ground = new Ground(WorldUtils.createGround(world));
addActor(ground);
}
private void setUpRunner() {
runner = new Runner(WorldUtils.createRunner(world));
addActor(runner);
}
Take again a look at the code. There is nowhere passed a Body object to the addActor method.
The only objects I see passed as parameters to the addActor method are runner & ground.
But those classes are extending the Actor class and not Body, see the code:
public class Runner extends GameActor { //..
and
public class Ground extends GameActor { //..
last not least the author of the code has defined the GameActor class like this:
public abstract class GameActor extends Actor { //..
==> you can see that those are subclasses of Actor and not Body. I hope it is clearer now.
BTW: if you use development environments like eclipse you can make use of the "Type Hierarchy" view!
Related
I am having a hard time getting this one piece of mocking figured out for my unit tests. The classes in question are all part of legacy code that I don't really have the option of changing right now (I am hoping to be able to do some refactoring in the future, but need tests now).
Here are the two classes that I am dealing with, and the specific part I am having trouble with. Class A declares an object using new and then class B uses the object. I am trying to mock the object but I keep getting the real version of it instead of the mocked version.
public class B extends A(){
...
int x = problemObj.doMethod();
}
public class A(){
...
ProblemObj problemObj = new ProblemObj();
}
Here is my test class.
#RunWith(PowerMockRunner.class)
#PrepareForTest({A.class, B.class})
public class ATest(){
private ProblemObj problemObjMock;
#Before
public void setUp(){
problemObj = PowerMockito.Mock(ProblemObj.class);
}
#Test
public void test(){
PowerMockito.whenNew(ProblemObj.class).withNoArguments().thenReturn(problemObj);
...//rest of test below here
}
}
I have done other whenNew mocking in tests and set it up the same way as this. But for some reason this object being in the superclass is really throwing me off.
Versions used are Junit:4.11, Mockito:1.9.5, Powermock: 1.6.6
I'm new to Windsor and am trying to get my head around how to do this in a standalone client (WPF in my case).
I have a class called a PictureWrapper that uses a PictureClient, like this:
public class PictureWrapper
{
private PictureClient myClient;
public PictureWrapper(int clientID)
{
myClient = new PictureClient();
//etc
}
}
In my PictureWrapper project, I can create a WindsorInstaller class that looks like this:
public class WindsorInstaller : IWindsorInstaller
{
public void Install(IWindsorContainer container, IConfigurationStore store)
{
container.Register(Component.For<IPictureClient>().ImplementedBy<PictureClient>().LifestyleTransient());
}
}
Assuming I call the Install() method above beforehand, here's where I get a little lost-- how exactly do I now create the PictureWrapper class in my WPF application? Do I still new() it up?
And given I'm not passing an instance of the PictureClient class in the PictureWrapper's constructor, how do I initialize it when creating the PictureWrapper?
I could, I suppose, make it a constructor parameter but when I create the PictureWrapper in the client, what do I pass to its constructor in my client? I'm trying to figure out how to get the DI ball rolling from my client, essentially.
my problem is pretty hard to describe and to google for <_< so ill give it a try here.
ihave my main.as, char.as, enemy.as, classes
my main was the stage of course.... it worked pretty well, but now that my main is extern too, it wont be called anymore...
it calls: char, enemy(which is a sub class of char) and then the empty stage but it never calls my main.as which should be called first...
also it never calls any constructors...how can i tell flash to start with my main.as?
i hope you got it, the code is probably to much to post here :P
If get you right.. you have to put super() calls to extended classes.
So for example in enemy class constructor:
public class enemy extends char {
function enemy() {
super(); // calls "char" class constructor
}
}
and if you have params in your constructors:
public class enemy extends char {
function enemy(param1: String, param2:String) {
super(param1, param2); // calls "char" class constructor
}
}
Overriding methods:
override public function doSome():void {
super.doSome(); // call parent class
}
and to make flash start with your main class - select your FLA file stage in flash (professional) and from the right side panel (properties) set Class to your main class (for example: com.myApp.Main).
Possibly bad practice but I'm not well versed in software design anyway (I'm sure this question would have been asked before but I can't seem to find the right terminology)...Anyhow, it's just another curiosity of mine I'd like to have answered.
So I have worked in a way where I type a base class variable to type Object or Sprite or something similar so that in my subclasses, I can instantiate my custom classes into them and store it. And when I access it, I just cast that variable to ensure I can access the methods.
Take this example, so that you know what I'm talking about:
public class BaseClass
{
protected var the_holder_var:Object;
public function BaseClass()
{
//Whatever abstract implementation here...
}
}
Now, my subclasses of that base class usually use an interface but for simplicity sake, I'll just write it without it.
public class AnExtendedClass extends BaseClass
{
public function AnExtendedClass()
{
//Instantiate my own class into the base class variable
this.the_holder_var = new ACustomClassOfMine();
//Then I can use the 'hackish' getter function below to
//access the var's functions.
this.holder_var.somefunction()
}
private function get holder_var():ACustomClassOfMine
{
return this.the_holder_var as ACustomClassOfMine;
}
}
This works and I'm sure it will make some ppl cringe (I sometimes cringe at it too).
So now, my question, is there a way to recast/retype that base var in my extended subclass?
kinda like this:
public class ExtendedClass extends BaseClass
{
//Not possible I know, but as a reference to see what I'm asking about
//Just want to change the type....
override protected var the_holder_var:ACustomClassOfMine;
public function ExtendedClass()
{
//Then I can forget about having that hackish getter method.
this.the_holder_var = new ACustomClassOfMine();
this.the_holder_var.somefunction();
}
}
I was thinking of typing most of my base class vars that I use as holders as type * and retyping them as I extend the class. (I could use it here too but yeah...)
Thoughts? Comments? Ideas?
I actually think your code (apart from the hypothetical addition at the end) is pretty alright. The practise of adding accessors to solve the type issue you're dealing with is a solid one. I would advise to rename the accessor to show it is a cast, maybe get holderVarAsCustom():ACustomClassOfMine (I'm also not a big fan of the underscores, that's another language's convention), but that's personal preference. What I'd do to solve your last problem is just create a matching setter function:
private function set holderVarAsCustom(value:ACustomClassOfMine):void {
this.the_holder_var = value;
}
This way you can access the correctly typed holder var for both read and write operations with complete type safety:
holderVarAsCustom = new ACustomClassOfMine();
holderVarAsCustom.someFunction();
I would definately advise against dropping the type safety by including arrays and what not, that just makes it unstable.
I must admit that i'm a little confused as to why you want to do this, but here goes. Could you not utilise the fact that Array's can hold different data types. So something like this:
public class BaseClass
{
protected var customStorage:Array;
public function BaseClass()
{
//Whatever abstract implementation here...
}
}
You could then access it with an associative method and a property:
public class AnExtendedClass extends BaseClass
{
private static const myName:String = "myName";
public function AnExtendedClass()
{
//Instantiate my own class into the base class variable
customStorage[myName] = new ACustomClassOfMine();
objectIWant.somefunction()
}
private function get objectIWant():ACustomClassOfMine
{
return ACustomClassOfMine(customStorage[myName]);
}
}
Is that any better?
I would not try to tinker this behaviour, since you can't change the declared type of a variable once declared, no matter how hard you try.
What I do in such cases, I either cast the variable if I use it sparingly or the object it references may change, or I add another variable with the type I want and let the other variable point to the new one. Like this:
public class A {
protected var object:Object;
public function A() {
//Whatever abstract implementation here...
}
}
and
public class B extends A {
protected var other:MyClass;
public function B() {
super();
this.other = new MyClass();
this.object = this.other;
}
}
Having it this way, class A uses the object via the this.object reference, and class B can use the this.other or both. But both references point to the same object. The only issues with this are:
having two references for in the same class to the same object is ugly (so are untyped variables and casts)
if the object one of them may point can change during runtime, you must be really carefull to synchronize these changes
I'm looking for ideas on how to implement a Mixin/Trait style system in AS3.
I want to be able to compose a number of classes together into a single object. Of course this is not a language level feature of AS3, but I'm hoping that there is maybe some way to do this using prototype based techniques or maybe some bytecode hacking that I believe AsMock uses to implement it's functionality.
An existing Java example is Qi4J where the user define interfaces that the Qi4j framework implements based on metadata tags and coding by convention.
Has anyone any ideas on how to get the Mixin/Trait concept working within AS3?
Zero solutions presented on this, so I looked into a few methods. There are ECMA script style mixins by adding methods defined on other objects to the base objects prototype. But this means that the advantages of static typing are gone.
I was looking for a solution that didn't sidestep the static type system. I knew that ASMock used bytecode injection to create proxy classes. I hacked around ASMock for the past few days and came up with a possible solution implemented by creating a class with composed classes (through bytecode injection).
From the users point of view this involves defining your object that uses mixins through many interfaces:
public interface Person extends RoomObject, Moveable
public interface RoomObject
{
function joinRoom(room:Room):void
function get room():Room
}
public interface Moveable
{
function moveTo(location:Point):void
function get location():Point
}
Then you define classes to represent these interfaces:
public class MoveableImpl implements Moveable
{
private var _location:Point = new Point()
public function get location():Point { return _location }
public function move(location:Point):void
{
_location = location.clone()
}
}
public class RoomObjectImpl implements RoomObject
{
private var _room:Room
public function get room():Room { return _room }
public function joinRoom(room:Room):void
{
_room = room
}
}
In a normal situation where you want to compose classes you would write:
public class PersonImpl implements Person
{
private var _roomObject:RoomObject = new RoomObjectImpl()
private var _moveable:Moveable = new MoveableImpl()
public function get room():Room { return _roomObject.room }
public function joinRoom(room:Room):void { _roomObject.joinRoom(room) }
public function get location():Point { return _moveable.location }
public function move(location:Point):void { _moveable.move(location) }
}
This is easily written using code due to it's regular layout. And that is exactly what my solution does, by injecting the equivilant bytecode into a new class. With this bytecode injection system we can create a Person object like so:
public class Main
{
private var mixinRepo:MixinRepository = new MixinRepository()
public function Main()
{
with(mixinRepo)
{
defineMixin(RoomObject, RoomObjectImpl) // associate interfaces with concreate classes
defineMixin(Moveable, MoveableImpl)
defineBase(Person)
prepare().completed.add(testMixins) // the injection is a async process, just liek in ASMock
}
}
private function testMixins():void
{
var person:Person = mixinRepo.create(Person)
var room:Room = new Room('room you can play in')
person.joinRoom(room)
trace('person.room:', person.room)
person.move(new Point(1, 2))
trace('person.location:', person.location)
}
}
At the moment this system is a proof of concept and is therefore very basic and brittle. But it shows that it is possible to come close to a Scala mixin/traits style system to AS3. I've made a github project to hold the code if anyone is interested in running the solution and poking around at how it was done.
A more complete example is given on the project wiki.
Look here, this works, mixes in methods and is simple.
http://github.com/specialunderwear/as3-mixin
o, and it works when you compile in as3 mode.
I found this one in Realaxy -- http://realaxy.com/