Checking if NSMutableArray contains values from another array

Question

I have an 3 NSMutableArray objects that contain CMTime objects. How can I iterate through all three of them in an efficient manner and find out if there are duplicate values in all three? For example, I'm iterating through one of time and reading the value and storing it in x. Now, I want to see if x occurs (at any position) within the other two arrays. I tried looking for a contains method, but couldn't find one. I did come across filterUsingPredicate, but I'm not sure if this is the best way of doing it nor how to actually use predicates.

I could do, but it would mean refactoring parts of the code and, ultimately, I need to convert it back to an array to work with some third party methods which may make it inefficient. I think fluchtpunkt's method should be ok. — XSL
– XSL, Commented Oct 6, 2011 at 21:46

Matthias Bauch · Accepted Answer · 2011-10-06 21:41:52Z

10

I tried looking for a contains method, but couldn't find one.

Use indexOfObject:

like this:

if ([array indexOfObject:object] != NSNotFound) {
    // object found
}
else {
    // object not found
}

answered Oct 6, 2011 at 21:41

Matthias Bauch

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Comments

andyvn22 · Accepted Answer · 2011-10-06 21:48:13Z

1

You can use ([yourArray indexOfObject:x] != NSNotFound) in place of your missing contains method. However, if you're doing this quickly, often, or with a lot of elements, you should consider using NSMutableOrderedSet, which is ordered like NSMutableArray, but offers a quick and efficient contains method, as well as allowing quick operations like union and intersection, which might allow you to redesign your algorithm to iterate through your elements much less.

answered Oct 6, 2011 at 21:48

andyvn22

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3 Comments

XSL Over a year ago

I will try the indexOf method and see if it becomes a bottleneck in performance. If so, I'll compare it with the Set and see if swapping between arrays and Sets is faster (as I need the final output to be an array so that it can be used in third party APIs).

andyvn22 Over a year ago

Very wise; don't prematurely optimize. Conversion to NSArray should be fast. There's an array method that returns a proxy that reflects changes in the original, which is cool.

XSL Over a year ago

Thanks for the info. I'm quite new to ObjC, so finding all these methods is very helpful.

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