Can I addobject to nsmutablearray only if addobject to nsset is successful?

Question

I only want to add unique objects to a set hence the reason I am using an NSSet. If an object is successfully added to that set I want to add an object to an array. Is there any way to do this? Can I make NSSet return something when an object is successfully added to it?

Answer 1

You could compare the count of the NSSet before and after attempting the add.

NSInteger setCount = [mySet count];
[mySet addObject:foo];
if ([mySet count] > setCount) {
    // object was added
}

You could also perform a containsObject test before adding the object:

if ([mySet containsObject:foo]) {
    // object already exists
} else {
    // object is not yet in the set
    [mySet addObject:foo];
    [myArray addObject:foo];
}

Yet another option is to simply add objects to a set, then convert the set to an array when you are done:

[mySet addObject:foo];
NSArray *myArray = [mySet allObjects];