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Declaring an object within an if scope?

BlitzMax Forums/BlitzMax Beginners Area/Declaring an object within an if scope?

Arkmon(Posted 2012) [#1]
Hello i cannot seem to able to declare an object within a score such as 
Type Yum
method Eat()

End Method
End Type


if Hello = False
WhatsUp:Yum = new Yum 'doesnt register'
Endif


if this isn't possible could i have some alternatives.

Last edited 2012

Last edited 2012

Last edited 2012


Arkmon(Posted 2012) [#2]
god damn bump


BladeRunner(Posted 2012) [#3]
Declare ist in front of your if / switch, if it is not used it will be null and eventually removed by the GC.


Arkmon(Posted 2012) [#4]
do you mean the declaration of the type?

could you possibly write it how it should?

Last edited 2012


Midimaster(Posted 2012) [#5]
[#Edited, because of Derron's adwise below:]

Why should this example not work? It works fine... but the scope of the object isn't limited on the IF...ENDIF but on the whole function( in this case MAIN() ) because you did not declare SUPERSTRICT. So it lives also behind ENDIF.

Graphics 800,600
Type Yum
	Field X%
	
	Method Eat()	
		Print "Eat it " + X
	End Method
End Type

If Hello = False
	WhatsUp:Yum = New Yum 
	WhatsUp.X:+1
	WhatsUp.Eat()
EndIf
Print "Press any key..."
WaitKey()
WhatsUp.X:+1
WhatsUp.Eat()



Do you later need the object outside the IF scope? Or do you want the object to be NULL outside?


If you want to set it null, do this:
SUPERSTRICT
...
Local Hello% = True
If Hello = True
	Local WhatsUp:Yum = New Yum 
	WhatsUp.X:+1
	WhatsUp.Eat()
EndIf
...



But If you still need it later, you should declare it before IF, because if IF was not true, the object would not be declared:

This causes an error in the second part:
SUPERSTRICT
...
Local Hello%=True
If Hello = 123
	Local WhatsUp:Yum = New Yum 
	WhatsUp.X:+1
	WhatsUp.Eat()
EndIf
Print "Press any key..."
WaitKey()
WhatsUp.X:+1
WhatsUp.Eat()



in this case this would be better:
...
Local WhatsUp:Yum = New Yum 
If Hello = 123
	WhatsUp.X:+1
	WhatsUp.Eat
	WhatsUp=Null
EndIf
Print "Press any key..."
WaitKey()
WhatsUp.X:+1
WhatsUp.Eat


[#EDIT]
I corrected my post, because I was wrong. Thanks Darron.

Last edited 2012


Derron(Posted 2012) [#6]
To avoid such obstacles...

use SUPERSTRICT ... it complains about not knowing "WhatsUp" after the "if"-phrase.

why= "local WhatsUp" is done WITHIN the scope of the "if hello...EndIf"-part.


If you do not use SuperStrict you will not be able to guarantee what an variable will be in different scopes (I think) - to avoid it, use SuperStrict and you will get compiler warnings if something is not obvious or just unclear to the compiler.

Maybe the following modification will show the difference (maybe uncomment the commented code)
[bbcode]
SuperStrict

Graphics 800,600
Type Yum
Field X%

'Method New:int(newX:int) 'also possible with params
Method New:int()
self.x:+1
End Method

Method Eat()
Print "Eat it " + X
End Method
End Type

runA()
print "runB:"
runB()

Function runA()
local Hello:int = false
If Hello = False
'register a local var
'WhatsUp only accessible in "IF Hello ...EndIF part"
Local WhatsUp:Yum = New Yum
WhatsUp.Eat
EndIf
'would be UNKNOWN
'Print "Press any key..."
'WaitKey()
'WhatsUp.X:+1
'WhatsUp.Eat
End Function

Function runB()
'register a local var (nulled atm)
'WhatsUp accessible in whole function "runB"
Local WhatsUp:Yum=null
local Hello:int = false
If Hello = False
WhatsUp = New Yum 'doesnt register'
WhatsUp.Eat
EndIf
Print "Press any key..."
WaitKey()
WhatsUp.X:+1
WhatsUp.Eat
End Function
[/bbcode]


matibee(Posted 2012) [#7]
Type manners
  Field ignore:Int
  Method Cost:Float()
    Return 0.0:Float
  End Method
End Type

Local you:manners
If welcome$ <> polite$
  you = New manners
  you.ignore = True
End If

If ( you <> Null ) Print you.Cost()



Arkmon(Posted 2012) [#8]
sorry for delayed post

thanks guys you guys went through alot of effort to write all that.