class Robot extends Canvas
{
public Robot() //constructor method - sets up the class
{
setSize(800,600);
setBackground(Color.WHITE);
setVisible(true);
}
public void paint( Graphics window )
{
window.setColor(Color.BLUE);
window.drawString("Robot LAB ", 35, 35 );
//call head method
//call other methods
}
public void head( Graphics window )
{
window.setColor(Color.YELLOW);
window.fillRect(300, 100, 200, 100);
//add more code here
}
How exactly do I call the head method?
I've tried multiple times, but I just can't seem to get it.
head(); window.head(); hasn't worked for me?
Sorry, I'm really new to this.
You need to use
head(window);
This is just how you call a method with parameters in Java (and most other languages), you put the parameters as a comma-separated list in the parentheses that follow the method name. Note that the parantheses are there even without any parameters.
methodWithNoParameters();
someOtherObject.methodWithNoParameters();
this.methodWithOneParameter("foo");
SomeClass.staticMethodWithFiveParameters(1,two,3,4, "five");
The number, order and types of the parameters must match what the method declaration has for its formal parameters. In your case public void(Graphics window) means there is just one.
Finally, you should make this method private if you only call it from inside paint (and not from outside of the class itself).
Related
I want to built a program which is get problems and I found that my first batches of tests involving custom components would tend to follow code:
import mx.core.Application;
import mx.events.FlexEvent;
import flexunit.framework.TestCase;
public class CustomComponentTest extends TestCase {
private var component:CustomComponent;
public function testSomeAspect() : void {
component = new CustomComponent();
component.addEventListener(FlexEvent.CREATION_COMPLETE,
addAsync(verifySomeAspect, 5000));
component.height = 0;
component.width = 0;
Application.application.addChild(component);
}
public function verifySomeAspect(event:FlexEvent) : void {}
override public function tearDown() : void {
try {
if (component) {
Application.application.removeChild(component);
component = null;
}
} catch (e:Error) {
}
}
First, you need to make sure the component has been fully initialized before you can reliably verify anything about it, and in Flex this happens asynchronously after it has been added to the display list. So you need to setup a callback (using FlexUnit's addAsync function) to be notified when that's happened.
Lately i've been just manually calling the methods that the runtime would call for you in the necessary places, so now my tests tend to look more like this:
import flexunit.framework.TestCase;
public class CustomComponentTest extends TestCase {
public function testSomeAspect() : void {
var component:CustomComponent = new CustomComponent();
component.initialize();
component.validateProperties();
}
This is much easier to follow, but it kinda feels like I'm cheating a little either way. The first case is slamming it into the current Application (which would be the unit test runner shell app), and the latter isn't a "real" environment.I was wondering how other people would handle this sort of situation?
I can agree that the second version is shorter, but I'm not sure that I think it's easier to follow. The test does a lot of things that you wouldn't normally do, whereas the first example is more true to how you would use the component outside the test environment.
Also, in the second form you have to make sure that you do exactly what the framework would do, miss one step and your test isn't relevant, and each test must repeat this code. Seems to me it's better to test it in a situation that is as close to the real thing as possible.
You could have a look at dpUint's sequences, they made component testing a little more declarative:
public function testLogin():void {
var passThroughData:Object = new Object();
passThroughData.username = "myuser1";
passThroughData.password = "somepsswd";
var sequence:SequenceRunner = new SequenceRunner(this);
sequence.addStep(new SequenceSetter(form.usernameTI,
{text:passThroughData.username}));
sequence.addStep(new SequenceWaiter(form.usernameTI,
FlexEvent.VALUE_COMMIT, 100));
sequence.addStep(new SequenceSetter(form.passwordTI,
{text:passThroughData.password}));
sequence.addStep(new SequenceWaiter(form.passwordTI, FlexEvent.VALUE_COMMIT, 100));
sequence.addStep(new SequenceEventDispatcher(form.loginBtn,
new MouseEvent("click", true, false)));
sequence.addStep(new SequenceWaiter(form, "loginRequested", 100));
sequence.addAssertHandler(handleLoginEvent, passThroughData);
sequence.run();}
I get this error when opening one specific form. The rest is working fine and I have no clue why this one isn't.
Error: An attempt has been made to Attach or Add an entity that is not new, perhaps having been loaded from another DataContext. This is not supported.
I get the error at _oDBConnection when I try to save. When I watch _oDBConnection while running through the code, it does not exist. Even when I open the main-window it does not exist. So this form is where the DataContext is built for the very first time.
Every class inherits from clsBase where the DataContext is built.
My collegue is the professional one who built it all. I am just expanding and using it (learned it by doing it). But now I'm stuck and he is on holiday. So keep it simple :-)
What can it be?
clsPermanency
namespace Reservation
{
class clsPermanency : clsBase
{
private tblPermanency _oPermanency;
public tblPermanency PermanencyData
{
get { return _oPermanency; }
set { _oPermanency = value; }
}
public clsPermanency()
: base()
{
_oPermanency = new tblPermanency();
}
public clsPermanency(int iID)
: this()
{
_oPermanency = (from oPermanencyData in _oDBConnection.tblPermanencies
where oPermanencyData.ID == iID
select oPermanencyData).First();
if (_oPermanency == null)
throw new Exception("Permanentie niet gevonden");
}
public void save()
{
if (_oPermanency.ID == 0)
{
_oDBConnection.tblPermanencies.InsertOnSubmit(_oPermanency);
}
_oDBConnection.SubmitChanges();
}
}
}
clsBase
public class clsBase
{
protected DBReservationDataContext _oDBConnection;
protected int _iID;
public int ID
{
get { return _iID; }
}
public DBReservationDataContext DBConnection
{
get { return _oDBConnection; }
}
public clsBase()
{
_oDBConnection = new DBReservationDataContext();
}
}
Not a direct answer, but this is really bad design, sorry.
Issues:
One context instance per class instance. Pretty incredible. How are you going to manage units of work and transactions? And what about memory consumption and performance?
Indirection: every entity instance (prefixed o) is wrapped in a cls class. What a hassle to make classes cooperate, if necessary, or to access their properties.
DRY: far from it. Does each clsBase derivative have the same methods as clsPermanency?
Constructors: you always have to call the base constructor. The constructor with int iID always causes a redundant new object to be created, which will certainly be a noticeable performance hit when dealing with larger numbers. A minor change in constructor logic may cause the sequence of constructor invocations to change. (Nested and inherited constructors are always tricky).
Exception handling: you need a try-catch everywhere where classes are created. (BTW: First() will throw its own exception if the record is not there).
Finally, not a real issue, but class and variable name prefixes are sooo 19xx.
What to do?
I don't think you can change your colleague's design in his absence. But I'd really talk to him about it in due time. Just study some linq-to-sql examples out there to pick up some regular patterns.
The exception indicates that somewhere between fetching the _oPermanency instance (in the Id-d constructor) and saving it a new _oDBConnection is created. The code as shown does not reveal how this could happen, but I assume there is more code than this. When you debug and check GetHashCode() of _oDBConnection instances you should be able to find where it happens.
I've just modified a method for handling my DDD commands (previously it had no return type):
public static CommandResult<TReturn> Execute<TCommand, TReturn>(TCommand command)
where TCommand : IDomainCommand
{
var handler = IoCFactory.GetInstance<ICommandHandler<TCommand, TReturn>>();
return handler.Handle(command);
}
The method is fine, and does what I want it to do, however using it creates some fugly code:
CommandResult<Customer> result =
DomainCommands.Execute<CustomerCreateCommand, Customer>
(
new CustomerCreateCommand(message)
);
Before I added the Customer return type TReturn, it was nice and tidy and the method could infer the types from its usage. However that's no longer possible.
Is there any way using any new C# features that I could rewrite the above to make it tidier, i.e. using Func, Action, Expression, etc? I'm probably expecting the impossible, but I'm getting fed up of writing so much code to just call a single method that used to be very simple.
One option to reduce it slightly is to have a static generic type for the type parameter that can't be inferred, allowing you to have a generic method with just one type parameter that can be inferred:
public static class DomainCommands<TReturn>
{
public static CommandResult<TReturn> Execute<TCommand>(TCommand command)
where TCommand : IDomainCommand
{
var handler = IoCFactory.GetInstance<ICommandHandler<TCommand, TReturn>>();
return handler.Handle(command);
}
}
Then:
var result = DomainCommands<Customer>.Execute(new CustomerCreateCommand(msg));
It's not much nicer, but it's slightly better. Of course, if the domain command type itself could be generic, that might help - so CustomerCreateCommand would implement IDomainCommand<Customer> for example. If you still needed a nongeneric IDomainCommand, you could make IDomainCommand<T> derive from IDomainCommand.
I have this situation where I want to use MEF in a chess project I'm workin on. Let's say I have a class constructor as in:
public class MoveManager
{
private Piece _piece;
public MoveManager(Piece piece)
{
_piece = piece;
}
Mode code here...
}
In this context I would have several classes that would derive from Piece like, Pawn, Rook, etc. If I put export attributes on all the classes the derive from Piece, the object being passed into the constructor is null. MEF loops through all classes the have the [Export(typeof(Piece))] and if it exceeds 1, it passes in null. So I cannot use MEF in this way. I'm going to use an Abstact Factory for getting the correct piece. Seems like the DI part of MEF can only take a single class that has the [Export(typeof(some base class))].
Can anyone shed some light on this?
I think you might be looking for the [Importing Constructor] arrtibute, which tells MEF how to use an exported class's constructor.
[Export(typeof(IPiece))]
class Pawn : IPiece
{
[ImportingConstructor]
public Pawn(ISomeDependency dep, [ImportMany] IEnumerable<IOtherDependency> depList)
{
//... do stuff with dependencies
}
}
This requires that an ISomeDependency is exported elsewhere (exactly once) and accepts any number of IOtherDependency's that might be exported too.
Supposing you did this with each piece, you could then:
[Export(typeof(IPieceList))]
class PieceList : IPieceList
{
[ImportingConstructor]
public PieceList([ImportMany] IEnumerable<IPiece> pieces)
{
// pieces now contains one of each piece that was exported above
}
}
I'm using Ninject 1.0 and would like to be able to inject lazy initialisation delegates into constructors. So, given the generic delegate definition:
public delegate T LazyGet<T>();
I'd simply like to bind this to IKernel.Get() so that I can pass a lazy getter into constructors, e.g.
public class Foo
{
readonly LazyGet<Bar> getBar;
public Foo( LazyGet<Bar> getBar )
{
this.getBar = getBar;
}
}
However, I can't simply call Bind<LazyGet<T>>() because it's an open generic type. I need this to be an open generic so that I don't have to Bind all the different lazy gets to explicit types. In the above example, it should be possible to create a generic delegate dynamically that invokes IKernel.Get<T>().
How can this be achieved with Ninject 1.0?
Don't exactly understand the question, but could you use reflection? Something like:
// the type of T you want to use
Type bindType;
// the kernel you want to use
IKernel k;
// note - not compile tested
MethodInfo openGet = typeof(IKernel).GetMethod("Get`1");
MethodInfo constGet = openGet.MakeGenericMethod(bindType);
Type delegateType = typeof(LazyGet<>).MakeGenericType(bindType);
Delegate lazyGet = Delegate.CreateDelegate(delegateType, k, constGet);
Would using lazyGet allow you to do what you want? Note that you may have to call the Foo class by reflection as well, if bindType isn't known in the compile context.
I am fairly certain that the only way to do this (without some dirty reflection code) is to bind your delegate with type params. This will mean it needs to be done for each individual type you use. You could possibly use a BindingGenerator to do this in bulk, but it could get a bit ugly.
If there is a better solution (a clean one) I would love to hear it as I run into this problem from time to time.
From another similar question I answered:
public class Module : NinjectModule
{
public override void Load()
{
Bind(typeof(Lazy<>)).ToMethod(ctx =>
GetType()
.GetMethod("GetLazyProvider", BindingFlags.Instance | BindingFlags.NonPublic)
.MakeGenericMethod(ctx.GenericArguments[0])
.Invoke(this, new object[] { ctx.Kernel }));
}
protected Lazy<T> GetLazyProvider<T>(IKernel kernel)
{
return new Lazy<T>(() => kernel.Get<T>());
}
}