Reflection questions

[nerobotParticipant]

Don’t know is it bug or impossible to implement..

I need to get name of template type, to do it I wrote this code:

Monkey

Method RemoveComponent<T>:Void() Where T Extends Component Local name:=Typeof( T ).Name 'error 🙁 RemoveComponent( name ) 'internal End

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Method RemoveComponent<T>:Void() Where T Extends Component Local name:=Typeof( T ).Name  'error RemoveComponent( name )  'internal End

and I got “Error : Identifier ‘T’ not found”.

Theory. When we call this method then ‘T’ *is* one of concrete type, so Typeof() *can* get it type. But error is at semant time not at compile.

For my luck, I find a solution – by adding optional parameter that we don’t need to use – it works with null-value.

Monkey

Method RemoveComponent<T>:Void( c:T=Null ) Where T Extends Component Local name:=Typeof( c ).Name 'works 🙂 RemoveComponent( name ) End

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Method RemoveComponent<T>:Void( c:T=Null ) Where T Extends Component Local name:=Typeof( c ).Name  'works RemoveComponent( name ) End

[nerobotParticipant]

Also I intrested in further improvement of reflection (generics, instance creation).

Is it possible to add into reflection module function like NewInstance( stringNameOfType:String )?

and use like this

Monkey

Local rect:=NewInstance( "Recti" ) rect.x=50 ; rect.y = 20 ; .....

1 2	Local rect:=NewInstance( "Recti" ) rect.x=50 ; rect.y = 20 ; .....

it looked not easy…

With this stuff we can get object-serializer.

[Mark SiblyKeymaster]

Use Typeof<> for ‘type expressions’ (eg: Typeof<mojo.Canvas>) and GetDecl( “New” )/Invoke() to create a class instance at runtime.

Check out my reflection blog post and the reflectiontest banana which should cover the basics, including creating a new class instance at runtime.

[nerobotParticipant]

Really.. thanks!

New question. Mark, please check this code. If we comment import of reflection – code works, else – don’t work.

Monkey

Namespace test.stack #Import "<std>" #Import "<mojo>" #Import "<reflection>" Using std.. Using mojo.. Function Main() Local awake:=New Awake Local awk:=Cast<IBehAwake>( awake ) Local stack:=New Stack<BehWrapper<IBehAwake>> RemoveFromStack( Varptr stack,awk,BehWrapper<IBehAwake>.Equals ) End Interface IBehAwake Method Awake() End Interface IEnabled Property isEnabled:Bool() End Class BehWrapper<T> Field state:IEnabled Field source:T Method New ( source:T,state:IEnabled ) Self.source=source Self.state=state End Function Equals:Bool( lhs:BehWrapper<T>,rhs:T ) Return lhs.source=rhs End End Class Awake Implements IBehAwake Method Awake() End End Function RemoveFromStack<T,V>:Bool( stackPtr:Stack<T> Ptr,value:V,equals:Bool( lhs:T,rhs:V ) ) Local stack:=stackPtr[0] For Local i:=0 Until stack.Length If equals( stack[i],value ) stack.Erase( i ) Return True Endif Next Return False End

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Namespace test.stack   #Import "<std>" #Import "<mojo>" #Import "<reflection>"   Using std.. Using mojo..     Function Main() Local awake:=New Awake Local awk:=Cast<IBehAwake>( awake ) Local stack:=New Stack<BehWrapper<IBehAwake>> RemoveFromStack( Varptr stack,awk,BehWrapper<IBehAwake>.Equals ) End     Interface IBehAwake Method Awake() End     Interface IEnabled Property isEnabled:Bool() End     Class BehWrapper<T> Field state:IEnabled Field source:T Method New ( source:T,state:IEnabled ) Self.source=source Self.state=state End Function Equals:Bool( lhs:BehWrapper<T>,rhs:T ) Return lhs.source=rhs End End     Class Awake Implements IBehAwake   Method Awake() End End     Function RemoveFromStack<T,V>:Bool( stackPtr:Stack<T> Ptr,value:V,equals:Bool( lhs:T,rhs:V ) ) Local stack:=stackPtr[0] For Local i:=0 Until stack.Length If equals( stack[i],value ) stack.Erase( i ) Return True Endif Next Return False End

[codifiesParticipant]

just a question

Monkey

[crayon-5cba85f219287819248445 inline="true" ] Local awk:=Cast<IBehAwake>( awake )

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[crayon-5cba85f219287819248445 inline="true" ] Local awk:=Cast<IBehAwake>( awake )

[/crayon]

you are casting something to an interface?

[nerobotParticipant]

Yes. Why not.

[Mark SiblyKeymaster]

Can you try and narrow it down?

Have no idea what it’s supposed to do and am feeling too lazy to try harder…

[Mark SiblyKeymaster]

Ok, definitely seems to be related to the stack ptr param for RemoveFromStack, just passing a plain stack works fine.

This should not of course cause a c++ error and I’ll check it out, but at the same time what’s up with the pointer?

Object Ptr’s (and array and function…well, ALL ptrs!) are dangerous. They can mean there’s nothing’s keeping an object alive so the object can be GC’d unexpectedly. They should only be used in extreme situations – generally dealing with extern libs or something.

I have kind of struggled with whether to or allow ptrs to GC-able objects at all or not but they’re in now so are staying, but be aware that if you use them needlessly in code posted here (without explanation) you will likely receive this lecture every time!

[nerobotParticipant]

I didn’t explain, sorry.

All I need is remove value from stack. But as stack is struct it passed in function as copy-of-stack, and my remove have no effect for original stack. I tried to use inerator, but I got error and did not understand this. And using of reference (via ptr) seems to be the easiest way for me. But now I tried iterator again and understand what I was doing wrong.

So, new code:

Monkey

Function RemoveFromStack<T,V>:Bool( iter:Stack<T>.Iterator,value:V,equals:Bool( lhs:T,rhs:V ) ) While Not iter.AtEnd If equals( iter.Current,value ) iter.Erase() Return True Endif iter.Bump() Wend Return False End

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Function RemoveFromStack<T,V>:Bool( iter:Stack<T>.Iterator,value:V,equals:Bool( lhs:T,rhs:V ) ) While Not iter.AtEnd If equals( iter.Current,value ) iter.Erase() Return True Endif iter.Bump() Wend Return False End

And usage:

Monkey

RemoveFromStack<BehWrapper<IBehAwake>,IBehAwake>( stack.All(),awk,BehWrapper<IBehAwake>.Equals )

1	RemoveFromStack<BehWrapper<IBehAwake>,IBehAwake>( stack.All(),awk,BehWrapper<IBehAwake>.Equals )

Yesterday I forgot to add prefix here ^

Monkey

<BehWrapper<IBehAwake>,IBehAwake>

1	<BehWrapper<IBehAwake>,IBehAwake>

and got unresolved types error (“Can’t find overload for …. with argument types ….)

[Mark SiblyKeymaster]

Stack is not a struct!

Stack, List, Map and Deque are all classes so instances are always passed by reference.

Also, I recently added a RemoveIf to stack (and list) which may be useful…

[nerobotParticipant]

Oh.. really. I keep opened stack.monkey2 file and don’t see that it’s a class, omg..

I found another error in my code, which I began to doubt in the stack work.

Big Thanks, Mark!

[Mark SiblyKeymaster]

I’m quite impressed you’ve done ted2go without knowing that!

[nerobotParticipant]

I know.. just need to be more attentive.

[Author]

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