NSArray
Documentation at the AppleDeveloperConnection:
See FoundationCollections for an overview; see DesignArray for a critique of the array design in general
NSArray implements -(BOOL)doesContain:(id)anObject which returns true if the array contains anObject, by identity.
Note that the same behavior can be gotten through documented methods with the following code:
- (BOOL)containsObjectIdenticalTo:(id)anObject
{
return NSNotFound != [self indexOfObjectIdenticalTo:anObject];
}
And in fact I imagine this is how -doesContain: is implemented.
Another excellent method that NSArray provides is -(void) makeObjectsPerformSelector:(SEL)aSel
[myArray makeObjectsPerformSelector:@selector(stroke)];
Yeah, but if they were thinking clearly, they would have returned a new array containing the results of each method call.
Like this?
- (NSArray )makeObjectsPerformSelectorAndReturnResults:(SEL)selector
{
NSMutableArray results = [[[NSMutableArray]] array];
NSEnumerator e = [self objectEnumerator];
id obj;
while (obj = [e nextObject])
{
if ([obj respondsToSelector:selector])
[results addObject:[obj performSelector:selector]];
}
return results;
}
Yeah, thanks! I didn't expect code...this could be useful.
There are several methods of this sort in cocoadev's NSArrayCategory.
I don't know if the code above should be considered reliable; there are lots of selectors where the methods don't return objects. Although I don't think there's any two method signatures with differing return types, there could be in the future. I've been working on a catch-all for this in another context. It's not done yet, but when it is I'll see about posting it.
Note that Cocoa already provides a similar method, via valueForKey:. These two lines are basically equivalent:
newArray = [array makeObjectsPerformSelectorAndReturnResults: @selector( someMethod )];
newArray = [array valueForKey: @"someMethod"];
As a bonus, the built-in method will autobox return values from methods that return primitives and it will also grab ivars directly if you provide its name and there's no accessor method.
Check out the -mapUsingSelector: method of the NSArray+Functional category: http://seriot.ch/software_cli.php#nsarray_functional
It allows you to do the same but with variable arguments selectors.
NSArray a = [[[NSArray]] arrayWithObjects:@"a", @"ab", @"abc", @"bc", @"c", nil];
NSArray x = [a filterUsingSelector:@selector(hasPrefix:), @"a", nil]; NSArray y = [a mapUsingSelector:@selector(uppercaseString), nil]; NSArray z = [a reduceUsingSelector:@selector(stringByAppendingString:)];
Results:
x: (a, ab, abc)
y: (A, AB, ABC, BC, C)
z: aababcbcc
Sample Code:
