reflection, getting Type instance name

BlitzMax Forums/BlitzMax Programming/reflection, getting Type instance name

TomToad

(Posted 2016) [#1]

I have a type, I create an instance of the type with New. I want to get the name of the instance, but the TypeID.Name() method returns the type name, not the instance name.

Type TMyType
	Field x:Float, y:Float
End Type

Local Dot:TMyType = New TMyType

Local ID:TTypeId = TTypeId.ForObject(Dot)

Print ID.Name() 'Prints "TMyType", but I want it to print "Dot"

Derron

(Posted 2016) [#2]

There is no reason for Objects to have "names".

Imagine instead of "Dot:TMyType" you have list containing various TMyType-Instances. They would not have a name - would they?

local dots:TList = CreateList
dots.AddLast( new TMyType)

So you'd better add a GUID/ID-system to your TMyType and then you could identify it by an manually or semi-automatically assigned name.

Type TMyType
  field ID:int = -1
  global lastID:int = 0

  Method New()
    lastID :+ 1
    ID = lastID
  End Method

  Method Init:TMyType(GUID:string)
    if GUID = "" then GUID = self.ID
    self.GUID = GUID
    return self
  End Method

... 
dots.AddLast( new TMyType.Init("dot") )

(above does not take care of clashes by manually assigning already used IDs as GUID)

bye
Ron

TomToad

(Posted 2016) [#3]

What I am doing is trying to create an error logging routine for the methods in my type. I want to print out which object is generating the error. The sample below is basically what I'm doing now, passing a Name to the Create function, but I want to default to the object name when no name is passed.

Type TPoint
	Field x:Float, y:Float
	Field Name:String
	
	Function Create:TPoint(x:Float, y:Float, Name:String = "")
		Local Point:TPoint = New TPoint
		If Name = "" 'Use object name as default name.  Doesn't work, will use "TPoint" for all objects.
			Local ID:TTypeId = TTypeId.ForObject(Point)
			Name = ID.Name()
		End If
		Point.Name = Name
		Point.x = x
		Point.y = y
		Return Point
	End Function
	
	Method Divide(Scale:Float)
		If Scale = 0.0 Then LogError("Divide by zero")
		x :/ Scale
		y :/ Scale
	End Method
	
	Method LogError(err:String)
		Print Name+": "+err
	End Method
End Type

Local Dot1:TPoint = TPoint.Create(100.0,150.0,"Dot1") 'If you remove the 3rd parameter, it defaults to TPoint instead of Dot1
Local Dot2:TPoint = TPoint.Create(150.0,200.0,"Dot2")

Dot1.Divide(2.0)
Dot2.Divide(0.0)

TomToad

(Posted 2016) [#4]

Thinking a bit more about it, I see what you are saying. The variable is only a placeholder for the object reference. Since the reference can be moved around (from variable to list, from list to another variable, etc...) there is no way to attach a name to it without explicitly giving it one (like my example above).

Local Dot1:TPoint = TPoint.Create(10,10) 'Object created
local Dot2:TPoint = Dot1 'Same Object, different variable holding the reference

Derron

(Posted 2016) [#5]

Yes ... exactly.

Instead of "reflection" you also could default a name to be something hand-written (in your case the class name ... name:string="TMyType"). When extending objects you use custom "Method New()"-methods which override the default name by doing a (name = "TMyExtendedType").

This way you could avoid the depths of the reflection code (might save some cpu cycles in tight loops).

bye
Ron