On 22/05/2008, at 3:09 PM, Andrew Farmer wrote:

On 21 May 08, at 21:48, Peter Zegelin wrote:
After all the talk about the best way to learn Cocoa I thought I'd better brush up on my obj-c. I've been able to get an amazing distance without really understanding a lot as I am mainly using Cocoa as a gui around some C++ code and have been able to get a long way just by wiring things up in IB and reusing some example code. However when messaging an object with multiple parameters I have never been able to use labeled arguments - only unlabeled. However on a hunch I removed the first label and it worked.

Brush up on your syntax a bit. You seem to misunderstand how ObjC method calls work.

Well thats what I am trying to do!



- (void)reset:(RulerStyle*)newStyle:(int)newSide:(int)textLoc: (double)newScale;

That syntax is pretty obscure. Try reading it as

- (void)reset:(RulerStyle*)style
    newStyle:(int)newStyle
     newSide:(int)newSide
     textLoc:(double)newScale;

and see if that makes any more sense. (Some of the types seem a little odd for the argument names, but that's what the method signature reads as.)

If this still doesn't make sense, check the header file for the code you're interfacing with.

I probably should have explained that I am calling my own ruler implementation so that object and method is my own. In C++ it is:

void reset(RulerStyle* newStyle, int newSide, int textLoc, double newScale);




So my question is - is there a way to include the first label? I note that the examples in the ObjectiveC manual seem to leave the first one out also:

[myRect setWidth:10.0 :15.0]; ---> [myRect setWidth:10.0 height: 15.0];

They shouldn't - that's invalid. Every "label" is a component of the method name - [myRect setWidth:10.0 height:15.0] is calling a completely separate method from [myRect setWidth:10.0 somethingElse: 15.0].

Well that example is straight out of the manual:

"Methods can also take arguments. The imaginary message below tells myRect to set its location within
the window to coordinates (30.0, 50.0):
[myRect setOrigin:30.0 :50.0];
Here the method name, setOrigin::, has two colons, one for each of its arguments. The arguments are inserted after the colons. This method name uses unlabeled arguments. Unlabeled arguments make it difficult to determine the kind and purpose of a method’s arguments. Instead, method names should include labels describing each of their arguments. Argument labels precede each colon in the method name. The setWidth:height: method, for example, makes the purpose of its two arguments
clear:
[myRect setWidth:10.0 height:15.0]; "


regards,

Peter


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