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Extended field types returning null

BlitzMax Forums/BlitzMax Programming/Extended field types returning null

Hezkore(Posted 2012) [#1]
I cannot figure out why this is returning "Blah" as blank, when it is clearly set!
SuperStrict

Type Test Abstract
	Global List:TList = New TList
	
	Field Blah:String
EndType

Type MyTest Extends Test
	Field Blah:String = "Yo yo"
End Type
Test.List.AddLast(New MyTest)

If Test.List.Count() <= 0 Then
	Print("Nothing in list!")
Else
	For Local t:Test = EachIn Test.List
		Print "Blah = " + t.Blah
	Next
EndIf



therevills(Posted 2012) [#2]
Do it this way:

SuperStrict

Type Test Abstract
	Global List:TList = New TList
	
	Field Blah:String = "Yo yo"
EndType

Type MyTest Extends Test
End Type

Test.List.AddLast(New MyTest)

If Test.List.Count() <= 0 Then
	Print("Nothing in list!")
Else
	For Local t:Test = EachIn Test.List
		Print "Blah = " + t.Blah
	Next
EndIf


Or:

SuperStrict

Type Test Abstract
	Global List:TList = New TList
	
	Field Blah:String
EndType

Type MyTest Extends Test
	Method New()
		Self.Blah = "Yo yo"
	EndMethod
End Type

Test.List.AddLast(New MyTest)

If Test.List.Count() <= 0 Then
	Print("Nothing in list!")
Else
	For Local t:Test = EachIn Test.List
		Print "Blah = " + t.Blah
	Next
EndIf


Because MyTest had its own version of Blah it was messing it up... in other languages I'm pretty sure it wouldn't even compile.

Last edited 2012


Hezkore(Posted 2012) [#3]
Well I want Blah to be "Yo yo" only in MyTest of course or I wouldn't have extended it, what if I had 4 or 5 Types extending Test, each with their own string in Blah?


Hezkore(Posted 2012) [#4]
Well I managed to do a workaround by using methodes that sets Blah for each Type.
It's quite ugly though (imo.)
SuperStrict

Type Test Abstract
	Global List:TList = New TList
	
	Field Blah:String
	
	Method SetBlah() Abstract
EndType

Type MyTest Extends Test
	Method SetBlah()
		Self.Blah = "My Test 1"
	End Method
End Type
Test.List.AddLast(New MyTest)

Type MyTest2 Extends Test
	Method SetBlah()
		Self.Blah = "My Test 2"
	End Method
End Type
Test.List.AddLast(New MyTest2)

If Test.List.Count() <= 0 Then
	Print("Nothing in list!")
Else
	For Local t:Test = EachIn Test.List
		t.SetBlah()
		Print "Blah = " + t.Blah
	Next
EndIf



Derron(Posted 2012) [#5]
Then you would have to adjust "Method New()" for each of the different types

(like done in the second "example").


In other languages like php you can do what you want (you create an custom field within your child - with the same name as in the parent) and are able to access it with eg. "super::myfieldname", if used with "$self->myfieldname" you access the local type-scope one..

But this is not available in blitzmax.

bye
Ron


Your "SetBla"-Thingy is nothing more than the "Method New()"-Type already proposed - except it uses a "SetValue"-Naming-Pattern which may confuse.

"SetXYZ" is normally for setting _private-fields or fields with special validation (ignore that sentence if you never will code in a team).
the "New"-Method is called whenever a special type-instance is created - so every time you create one of the children.

Last edited 2012


Hezkore(Posted 2012) [#6]
Yeah I'm using Method New() now, he didn't write that the first time, it was edited in after I had already done SetBlah()