Reflections on Reflection

Tagged: reflection

This topic contains 3 replies, has 2 voices, and was last updated by Mark Sibly 1 year, 7 months ago.

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September 17, 2017 at 7:53 am #10572

Ethernaut

Participant

I’m trying to get the value of a DeclInfo object as a String.

The Get() method returns a Variant. I’m trying to cast the variant, but it keeps failing. What do I have to do to cast a Variant? In the code below, I tried a case-by-case casting, but that still doesn’t work:

Method List()
	Local info :TypeInfo = Self.InstanceType
	
	Print info.Name	'class name
	
	For Local decl:DeclInfo = Eachin info.GetDecls()	'all fields

		If( ( decl.Kind = "Field" ) Or ( decl.Kind = "Global" ) ) And decl.Settable
			Print "    " + decl.Name + ": " + decl.Type + " = "' + StringFromDecl( decl )
		End
		
	Next
End

Method StringFromDecl:String( d:DeclInfo )
	Select d.Type.Name
	Case "Double" Return String( Cast<Double>( d.Get( d ) ) )
	Case "Float" Return String( Cast<Float>( d.Get( d ) ) )
	Case "String" Return String( Cast<String>( d.Get( d ) ) )
	Case "Bool" Return ( Cast<Bool>( d.Get( d ) )? "True" Else "False"  )
	Case "Float[]" Return "[]"
	Case "String[]" Return "[]"
	End
	Return "invalid type"
End

Method List()

Local info :TypeInfo = Self.InstanceType

Print info.Name 'class name

For Local decl:DeclInfo = Eachin info.GetDecls() 'all fields

If( ( decl.Kind = "Field" ) Or ( decl.Kind = "Global" ) ) And decl.Settable

Print " " + decl.Name + ": " + decl.Type + " = "' + StringFromDecl( decl )

End

Method StringFromDecl:String( d:DeclInfo )

Select d.Type.Name

Case "Double" Return String( Cast<Double>( d.Get( d ) ) )

Case "Float" Return String( Cast<Float>( d.Get( d ) ) )

Case "String" Return String( Cast<String>( d.Get( d ) ) )

Case "Bool" Return ( Cast<Bool>( d.Get( d ) )? "True" Else "False" )

Case "Float[]" Return "[]"

Case "String[]" Return "[]"

End

Return "invalid type"

End

One mo’ question:

TypeInfo.GetDecls() returns ALL decls, Public, Private, Protected, etc. Is there a way to filter only the public ones (without changing the way they’re named)?

Thanks!

September 20, 2017 at 9:03 pm #10653

Ethernaut

Participant

Answering my own questions, if anyone has the same questions:

Where it says “d.Get( d )”, it should say “d.Get( Self )”, since we’re calling this method from the instance I’m inspecting. Duh!
Couldn’t filter by “Public”, but there’s an undocumented DeclInfo.Kind, “Property” (docs only mention Field, Global, Method and Function). That’s actually good enough for me.

Cheers!

September 20, 2017 at 9:21 pm #10654

Mark Sibly

Keymaster

What do you mean by failing – what error are you getting/

Can you post something buildable/runnable?

September 20, 2017 at 10:05 pm #10655

Mark Sibly

Keymaster

Beat me to it! Yes, Kind needs to be documented (supposedly is…). Will add IsPublic, IsProtected, IsPrivate (or equivalent) too.

#Import "<reflection>"

Class C
	Field i:Int
End

Function ToString:String( d:DeclInfo,instance:Variant )
	
	Select d.Type
	Case Typeof<Int> Return String( Cast<Int>( d.Get( instance ) ) )
	End
	
	Return "<error>"
	
End

Function Main()
	
	Local c:=New C
	
	c.i=100
	
	Local type:=c.InstanceType
	
	For Local d:=Eachin type.GetDecls()
		
		Select d.Kind
		Case "Field"
			Print d.Kind+" "+d.Name+"="+ToString( d,c )
		End
		
	Next

End

#Import "<reflection>"

Class C

Field i:Int

End

Function ToString:String( d:DeclInfo,instance:Variant )

Select d.Type

Case Typeof<Int> Return String( Cast<Int>( d.Get( instance ) ) )

End

Return "<error>"

End

Function Main()

Local c:=New C

c.i=100

Local type:=c.InstanceType

For Local d:=Eachin type.GetDecls()

Select d.Kind

Case "Field"

Print d.Kind+" "+d.Name+"="+ToString( d,c )

End

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