CODEWITHSUNDEEP
iphoneiosobjective-cipad
adit
adit

Reputation: 33684

adding each element of NSMutableIndexSet by 1

I have a NSMutableIndexSet and I want to be able to add and store the index set by 1, planning to use a block to do it, here's what I have so far:

[indexes enumerateIndexesUsingBlock:^(NSUInteger idx, BOOL *stop) {
            //add and store back the set here
            idx++;
}];

is there a way to iterate and modify at the same time? if yes how? the code above doesn't seem to work

Upvotes: 1

Views: 888

Answers (1)

zaph
zaph

Reputation: 112873

You can not enumerate and modify the NSMutableIndexSet you are enumerating. Just create a new NSMutableIndexSet and add the entries to it. It is doubtful that there is a performance hit.

Example (with ARC):

NSMutableIndexSet *originalIndexSet = [NSMutableIndexSet new];
[originalIndexSet addIndex:1];
[originalIndexSet addIndex:5];

NSMutableIndexSet *newIndexSet = [NSMutableIndexSet new];
[originalIndexSet enumerateIndexesUsingBlock:^(NSUInteger idx, BOOL *stop) {
    [newIndexSet addIndex:idx+1];
}];

NSLog(@"originalIndexSet: %@", originalIndexSet);
NSLog(@"newIndexSet:      %@", newIndexSet);

Then 

originalIndexSet = newIndexSet;

NSLog output:

originalIndexSet: [number of indexes: 2 (in 2 ranges), indexes: (1 5)]
newIndexSet: [number of indexes: 2 (in 2 ranges), indexes: (2 6)]

Upvotes: 4

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