Don't understand multiple parameter declarations in objective-c

can someone clarify this for me:

When there’s more than one argument, the arguments are declared within the method name after the colons. Arguments break the n开发者_JAVA技巧ame apart in the declaration, just as in a message. For example:

- (void)setWidth:(float)width height:(float)height;

So in the above:

1. method is for instance variables
2. returns void
3. parameter#1 is a float, named width.
4. parameter#2 is a float,named height.

But why is it hieght:(float)height; and not just:

- (void)setWidth: (float)width (float)height;

Objective-C does not have named arguments. Nor does it have "keyword arguments".

Objective-C uses what is called "interleaved arguments". That is, the name of the method is interleaved with the arguments so as to produce more descriptive and readable code.

[myObject setWidth:w height:h];

The above reads, effectively, as tell myObject to set the width to w and height to h.

In the above case, the method's name -- its selector -- is exactly setWidth:height:. No more, no less.

This is all explained in the Objective-C guide.

That's just a feature of Objective-C to make your life easier when reading the method invocation, which would look like:

[myObject setWidth:w height:h];

You can leave the labels out (except the first one), so if you really want to, you can have:

-(void)setWidth:(float)width :(float)height
{
  ...
}

and use it as:

[myObject setWidth:w :h];

But that's not really in the spirit of the Objective-C language. The entire point of those labels is to make those calls easier to understand without having to look up the method definition.

The fact that the argument name happens to also be in the method name is confusing you. Think about how you actually call it:

[something setWidth:500 height:250];

Following your suggestion, it would be something like this instead:

[something setWidth:500 250]; // That 250 is just kind of hanging 
                              // out there — not very readable

You could also give the argument a totally different name from the part of the method name that precedes it:

- (void)setGivenName:(NSString *)first surname:(NSString *)last