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Re: Objective-C parameter mutation
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Re: Objective-C parameter mutation


  • Subject: Re: Objective-C parameter mutation
  • From: Chris Idou <email@hidden>
  • Date: Wed, 15 Oct 2008 17:41:56 -0700 (PDT)

Works for me.

-(void)aMethod:(void *)mem {
	NSLog(@"mem2: %d", mem);
}


- (void)awakeFromNib {
	void *memory = malloc(1);
	NSLog(@"mem1: %d", memory);
	[self aMethod:memory];
}

2008-10-16 11:40:36.815 aProg[30378:813] mem1: 2439440
2008-10-16 11:40:36.815 aProg[30378:813] mem2: 2439440


--- On Wed, 10/15/08, James Trankelson <email@hidden> wrote:

> From: James Trankelson <email@hidden>
> Subject: Objective-C parameter mutation
> To: "cocoadev List" <email@hidden>
> Date: Wednesday, October 15, 2008, 5:31 PM
> Hi,
>
> I have a question about method parameters in Objective C. A
> long time
> ago, I had a method like the following:
>
> -(void) foo:(float)val { }
>
> ... and when I would call it ([inst foo:0.001], for
> example), the
> value inside the foo method would NOT be 0.001. At the
> time, I
> believed there to be an Objective C requirement that
> parameters to
> methods need to be pointers to objects, not primitive
> values. So, I
> achieved success by changing the above method declaration
> to
>
> -(void) foo:(NSNumber*)val { }
>
> ... and passing in a NSNumber* with a float value worked.
>
> Now, I'm having the same problem, but am not convinced
> there is any
> such requirement that parameters be pointers to object
> instances. (I
> could be wrong, though)
>
> So, I've got the following method:
>
> + (void)done:(MyObj*)dObj structure:(void*)pStruct
>
> ... and when I call it with a "structure"
> parameter, say a malloc'ed
> char* at address 0x171eb070, as soon as I step into this
> method, the
> address is no longer 0x171eb070, but some garbage value
> that causes
> all sorts of trouble. Here's to hoping someone can tell
> me why this
> doesn't work...
>
> Thanks
>
> jt
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References: 
 >Objective-C parameter mutation (From: "James Trankelson" <email@hidden>)

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