Removing duplicate strings from array

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Level 1

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Removing duplicate strings from array

I have a Cocoa application that contains an NSMutableArray of NSString objects. I want to remove all duplicate entries from the array (i.e., those strings with the same text, but not necessarily the same object addresses).

I'm thinking perhaps that sortedArrayUsingDescriptors: looks promising, but I'm quite confused as to how to use descriptors. The discussion in the documentation is formidable to say the least.

Any suggestions? Thanks in advance.

Eric

MacBook Pro, Mac OS X (10.5.2)

Posted on May 3, 2008 7:36 AM

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Answer 1

May 3, 2008 8:26 AM in response to Eric S

Do you want to remove just the duplicates or both the duplicates and the originals as well? If you want to remove just the duplicates then take a peek at NSSet and NSMutableSet.

Now, let me just say that, I don't know Objective-C but in Java, which I do know, NSSet and NSMutableSet use the equals(Object) method to compare objects so that even if two strings are different objects they'll still be considered the same string if equals(Object) returns true. I don't know if this happens in Objective-C but it's worth taking a look.

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Answer 2

Eric S Author

Level 1

95 points

May 3, 2008 1:59 PM in response to Eric S

Hmmmm... thanks for the thought but I'm not seeing anything that would work in NSSet.

Basically, if I have an array of strings: "apple", "cat", "dog", "cat", "green"

I want to end up with: "apple", "cat", "dog", "green"

How does one do this in Cocoa?

e

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Answer 3

May 3, 2008 2:44 PM in response to Eric S

NSMutableSet will only accept one object of a given value. So if you call the method addObjectsFromArray(NSArray) with the array "apple", "cat", "dog", "cat", "green" then you'll end up with a set that contains "apple", "cat", "dog", "green". Then simply call the method allObjects() to get back an NSArray.

Message was edited by: GalenRhodes

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Answer 4

etresoft

Level 9

57,002 points

May 3, 2008 2:45 PM in response to Eric S

Eric S wrote:
Hmmmm... thanks for the thought but I'm not seeing anything that would work in NSSet.

Take another look. You want NSMutableSet. If you add to it: "apple", "cat", "dog", "cat", and "green", it will contain: "apple", "cat", "dog", "green".

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