Sorting an NSArray of NSString

Question

Can someone please show me the code for sorting an NSMutableArray? I have the following NSMutableArray:

NSMutableArray *arr = [[NSMutableArray alloc] init];

with elements such as "2", "4", "5", "1", "9", etc which are all NSString.

I'd like to sort the list in descending order so that the largest valued integer is highest in the list (index 0).

I tried the following:

[arr sortUsingSelector:@selector(compare:)];

but it did not seem to sort my values properly.

Can someone show me code for properly doing what I am trying to accomplish? Thanks!

Solution 1

It's pretty simple to write your own comparison method for strings:

@implementation NSString(compare)

-(NSComparisonResult)compareNumberStrings:(NSString *)str {
    NSNumber * me = [NSNumber numberWithInt:[self intValue]];
    NSNumber * you = [NSNumber numberWithInt:[str intValue]];

    return [you compare:me];
}

@end

Solution 2

You should use this method:

[arr sortedArrayUsingSelector:@selector(caseInsensitiveCompare:)];

in a NSArray or:

[arr sortUsingSelector:@selector(caseInsensitiveCompare:)];

in a "inplace" sorting NSMutableArray

The comparator should return one of this values:

• NSOrderedAscending
• NSOrderedDescending
• NSOrderedSame

Solution 3

If the array's elements are just NSStrings with digits and no letters (i.e. "8", "25", "3", etc.), here's a clean and short way that actually works:

NSArray *sortedArray = [unorderedArray sortedArrayUsingComparator:^(id a, id b) {
    return [a compare:b options:NSNumericSearch];
}];

Done! No need to write a whole method that returns NSComparisonResult, or eight lines of NSSortDescriptor...

Solution 4

IMHO, easiest way to sort such array is

[arr sortedArrayUsingDescriptors:@[[NSSortDescriptor sortDescriptorWithKey:@"self.intValue" ascending:YES]]]

If your array contains float values, just change key to self.floatValue or self.doubleValue

Solution 5

The easiest way would be to make a comparator method like this one

NSArray *sortedStrings = [stringsArray sortedArrayUsingComparator:^NSComparisonResult(NSString *firstString, NSString *secondString) {
    return [[firstString lowercaseString] compare:[secondString lowercaseString]];
}];

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Comments

[CodeGuy]

I tried that second way and here is the output of a sorted array:

[CodeGuy]

2, 2, 2, 2, 3, 3, 32, 4, 47, 477, 56, 7, 8

[HyLian]

You need to replace the comparator given in the example, i didn't know what was you sorting "criteria" :)

[Martin]

You need to declare a & b as id otherwise Xcode will produce an error : [unorderedArray sortedArrayUsingComparator:^(id a, id b) {...}];

[ReDetection]

this won't help when you have numbers in string (as in question)

[damianostre]

It also works with strings that contain non-digits, e.g. "File 1", "File 2", etc. - it will then correctly sort "File 2" before "File 12".