Question

Is there a more concise way to do the following in iOS?

Suppose we have:

NSArray *existingArray;

and also our object self has a method someMethod which can take the objects in existingArray as input and returns objects of class Foo. We could create a new array *derivedArray by applying someMethod to the objects in existingArray as follows:

NSMutableArray *derivedArray = [[NSMutableArray alloc]init];
for (id obj in existingArray) {
  [derivedArray addObject: [self someMethod: obj]];
}

My question is, is there a more concise way to do that? Something like:

NSArray *derivedArray = [existingArray arrayByMappingMethod: someMethod withObject: self];  

Answer 1

No. There is a makeObjectsPerformSelector: method (and a few other related ones), but none allow you to get a result from the calls. You could, of course, add your method as a category on NSArray, but Apple has not provided a method to do this.

In terms of performance improvements, change

[[NSMutableArray alloc] init];

to

[[NSMutableArray alloc] initWithCapacity:[existingArray count]];

This will allow the array to allocate memory for all of the objects at once, instead of reallocating every time you add an object.