x=New x error
BlitzMax Forums/BlitzMax Programming/x=New x error
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| I know this is not supposed to work, but sometimes I get a windows error message when I do this on accident is there some OOP thing that is why this compiles? strict Type tbat Field x EndType Local i:int Local bat:tbat Print "hi" 'bat=New i 'does not compile. ok bat=New bat 'compiles. why? |
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| I think bat being null when you do it is the problem. New, when passed an object instead of a type name, will create a new object of the same type as that object, but if that object is null it shouldn't work. |
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| ok thanks, thats really wierd. [this works] Type person Field name:String EndType Local bob:person Local joe:person joe=New person bob=New joe BOB EQUALS NEW JOE. (works only if joe happens to be not null at the time, even though joe is always declared as a person) |
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| What's weird about that? |
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| on the first sample new only accepts types. it does the same as "new" in c like languages: it creates a new instance of the class / type you tell it. There is no type "i" ( as well as "int" etc are no types that can be instanced ) and the second sample: new requires, as mentioned above, the TYPE, not a variable ( see the helpfiles on userdefined types for further informations ) |
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| On the "bob=New joe" sample, the compiler should be puking because "joe" isn't a type. Looks like a compiler bug... |
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| and the second sample: new requires, as mentioned above, the TYPE, not a variable ( see the helpfiles on userdefined types for further informations ) my code works on the second example. |
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| Damn, I wrote a test program and was thinking, hmm, maybe Mark made that a way to do copy construction, but no. How about that Mark? Aaron |
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| heh ya, that would explain why it works only when joe is not null, (in bob:person=new joe) But it should be fixed that it gives a windows program crash (in a similar situation) with debug ON. that shouldnt ever happen with debug on. |
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| As I said, New, when passed an object instead of a type name, will create a new object of the same type as that object It's a documentation issue. The feature is so you can do something like this - which *doesn't* work, because SizeOf is incorrectly returning 0: Type CloneableObject Method Clone:Object( ) Local sel:Object = Self Local obj:Object = New sel MemCopy( Byte Ptr( Varptr( obj ) ), Byte Ptr( Varptr( sel ) ), SizeOf( sel ) ) Return obj End Method End Type Type Enemy Extends CloneableObject Field x#, y# End Type Local BadGuy:Enemy = New Enemy BadGuy.x = 50 BadGuy.y = 60 Local AnotherBadGuy:Enemy = Enemy( BadGuy.Clone( ) ) RuntimeError AnotherBadGuy.x + "," + AnotherBadGuy.y |
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