On May 21, 2008, at 10:25 PM, Peter Zegelin wrote:
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]; "
Objective-C does not have named arguments. Nor does it have keyword
arguments.
Those are two different methods; two different selectors, to be
precise.
The first example invokes the method named -- whereby "method name" is
synonymous with "selector" -- "setOrigin::".
The second example invokes the selector "setWidth:height:".
That is, those two lines of code would work if and only if "myRect"
implemented BOTH methods that could likely be declared as:
- (void) setOrigin: (float) x :(float) y;
- (void) setWidth: (float) x height: (float) y;
The paragraph implies that the methods are different, but doesn't
state it explicitly. If I were writing this, I might say:
....
Methods can also take arguments. The imaginary message below tells
the myRect object to set its origin to the coordinates (30.0, 50.):
[myRect setOrigin:30.0 :50.0];
The method is named "setOrigin::". It has two colons as it takes two
arguments. This particular method does not interleave the method
name with the arguments and, thus, the second argument is effectively
unlabeled and it is difficult to determine the kind or purpose of the
method's arguments.
Instead, method names should interleave the name with the arguments
such that the method's name naturally describes the arguments expected
by the method. For example, the myRect class could instead implement
a "setOriginX:y:" method that makes the purpose of its two arguments
clear:
[myRect setOriginX: 30.0 y: 50.0];
....
b.bum
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