Sorting array containing strings in objective c

Question

I have an array named 'names' with strings looking like this: ["name_23_something", "name_25_something", "name_2_something"]; Now I would like to sort this array in ascending order so it looks like this: ["name_25_something", "name_23_something", "name_2_something"];

I guess that should start of with extracting the numbers since I want that the sorting is done by them:

for(NSString *name in arr) {
    NSArray *nameSegments = [name componentsSeparatedByString:@"_"];
    NSLog("number: %@", (NSString*)[nameSegments objectAtIndex:1]);     
}

I'm thinking of creating a dictionary with the keys but I'm not sure if that is the correct objective-c way, maybe there some some methods I could use instead? Could you please me with some tips or example code how this sorting should be done in a proper way.

Thank you

Ed Marty · Accepted Answer · 2010-05-08 14:23:47Z

2

@implementation NSString (MySort)

- (int) myValue {
    NSArray *nameSegments = [self componentsSeparatedByString:@"_"];
    return [[nameSegments objectAtIndex:1] intValue];
}

- (NSComparisonResult) myCompare:(NSString *)other {
    int result = [self myValue] - [other myValue];
    return result < 0 ? NSOrderedAscending : result > 0 ? NSOrderedDescending : NSOrderedSame;
}

@end

...

arr = [arr sortedArrayUsingSelector:@selector(myCompare:)];

answered May 8, 2010 at 14:23

Ed Marty

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Comments

user23743 · Accepted Answer · 2010-05-08 13:52:21Z

2

Check out -[NSArray sortedArrayUsingComparator:].

answered May 8, 2010 at 13:52

user23743

2 Comments

Ed Marty Over a year ago

Unfortunately not available on the iPhone OS.

user23743 Over a year ago

@ed: no, but a little inhibative use of the scroll bar takes us from that entry in the documentation to the plethora of other ‘-sortedArrayUsing…‘ methods.

jakob · Accepted Answer · 2010-05-08 14:39:28Z

1

Thank you for your answers!

I did like this, what do you think:

NSInteger sortNames(id v1, id v2, void *context) {
    NSArray *nameSegments = [(NSString*)v1 componentsSeparatedByString:@"_"];
    NSArray *nameSegments2 = [(NSString*)v2 componentsSeparatedByString:@"_"];
    int num1 = [[nameSegments objectAtIndex:1] integerValue];
    int num2 = [[nameSegments2 objectAtIndex:1] integerValue];
    if (num1 < num2)
        return NSOrderedDescending;
    else if (num1 > num2)
        return NSOrderedAscending;

    return NSOrderedSame;
}

names = [names sortedArrayUsingFunction:sortNames context:nil];

This will result in:

["name_25_something", "name_23_something", "name_2_something"];

answered May 8, 2010 at 14:39

jakob

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1 Comment

iPadDeveloper2011 Over a year ago

That looks good, apart from the name of the function. compareNames would be better.

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