CODEWITHSUNDEEP
objective-cnsarray
gypsyDev
gypsyDev

Reputation: 1299

Multiple NSArray's and common objects

So I have multiple NSArrays(5 actually), and I would like to create a new NSArray containing only objects common to ALL arrays. Is there an efficient way to do this. The only way I can think of, is to loop through all the arrays comparing each object.

Upvotes: 1

Views: 1302

Answers (2)

gypsyDev
gypsyDev

Reputation: 1299

I ended up using this which works quite well:

NSMutableSet *set = [NSMutableSet setWithArray:array];
NSMutableSet *set1 = [NSMutableSet setWithArray:array2];
NSMutableSet *set2 = [NSMutableSet setWithArray:array3];
NSMutableSet *set3 = [NSMutableSet setWithArray:array4];
NSMutableSet *set4 = [NSMutableSet setWithArray:array5];

[set intersectSet:set1];
[set intersectSet:set2];
[set intersectSet:set3];
[set intersectSet:set4];

NSArray *allArray = [set allObjects];

Upvotes: 4

aroth
aroth

Reputation: 54796

Why not create an NSSet (NSMutableSet, really), dump the contents of all 5 arrays into it, and then construct a new NSArray from the NSSet?

Sorry, I misread your question originally. Yes, I think you pretty much have to loop through each one to find the duplicates. But it's not so terrible to implement (might be somewhat slow at runtime if your arrays are huge, however).

Here's some example code:

- (void) filterSet: (NSMutableSet*)set withArray: (NSArray*) array {
    NSMutableSet* removals = [NSMutableSet setWithCapacity:[array count]];
    for (id obj in set) {
        if (! [array containsObject: obj]) {
            [removals addObject: obj];
        }
    }
    [set minusSet: removals];
}

NSMutableSet* mySet = [NSMutableSet setWithCapacity:[array1 count] * 5];
[mySet addObjectsFromArray: array1];
[self filterSet: mySet withArray: array2];
[self filterSet: mySet withArray: array3];
[self filterSet: mySet withArray: array4];
[self filterSet: mySet withArray: array5];

NSArray* filteredArray = [mySet allObjects];

Upvotes: 3

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