how to sort array of strings

I create an array with string names as shown below

NSMutableArray *strings = [[NSMutableArray alloc]init];
[string addObject:@"string1"];
[string addObject:@"string2"];
[string addObject:@"string3"];
[string addObject:@"string4"];

and I create a button. Whenever I click the but开发者_开发百科ton the strings are exchanged how can I do this?

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EDIT:

Looks like you do not really lack basic knowledge. You can call this method in NSArray after you add your objects:

This method is the simplest way to do your job:

NSArray *sortedStrings = [strings sortedArrayUsingSelector:@selector(compare:)];

More about sortedArrayUsingSelector:

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You can see NSArray class reference about following methods.

Sorting

• sortedArrayHint
• sortedArrayUsingFunction:context:
• sortedArrayUsingFunction:context:hint:
• sortedArrayUsingDescriptors:
• sortedArrayUsingSelector:
• sortedArrayUsingComparator:
• sortedArrayWithOptions:usingComparator:

As for your problem, you can sort strings by
[strings sortedArrayUsingSelector:@selector(compare:)].