Sorting mutable array by dictionary key

问题

I have already looked through a few answers using the various sorting methods of NSMutableArray, but for some reason they are not working for me.

I am just trying to sort the mutable array which contains dictionaries by the Delay key within each dictionary. However, the "sorted" array is the exact same as the original array.

By the way, it works fine if I create a dummy mutable array and populate it with dictionaries containing numbers, but for some reason it won't sort this mutable array that I am initializing.

What am I doing wrong?

Here's my code:

playlistCalls = [[NSMutableArray alloc] initWithArray:[currentPlaylist objectForKey:@"Tunes"]];

NSLog(@"original %@", playlistCalls);

NSSortDescriptor *delay = [NSSortDescriptor sortDescriptorWithKey:@"Delay" ascending:YES];
[playlistCalls sortUsingDescriptors:[NSArray arrayWithObject:delay]];

NSLog(@"sorted %@", playlistCalls);

Here's the array containing the dictionaries:

2012-06-04 15:48:09.129 MyApp[57043:f503] original (
        {
        Name = Test Tune;
        Delay = 120;
        Volume = 100;
    },
        {
        Name = Testes;
        Delay = 180;
        Volume = 100;
    },
        {
        Name = Testing;
        Delay = 60;
        Volume = 100;
    }
)

2012-06-04 15:48:09.129 MyApp[57043:f503] sorted (
        {
        Name = Test Tune;
        Delay = 120;
        Volume = 100;
    },
        {
        Name = Testes;
        Delay = 180;
        Volume = 100;
    },
        {
        Name = Testing;
        Delay = 60;
        Volume = 100;
    }
)

回答1:

The code above is fine when I use NSNumbers in my dictionary. That leads me to believe that the Delay value is stored as strings in your dictionary. What you will need to do then is sort by the strings integerValue.

NSSortDescriptor *delay = 
   [NSSortDescriptor sortDescriptorWithKey:@"Delay.integerValue" ascending:YES];

回答2:

Please try the following, it worked with me

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

dic = [NSDictionary dictionaryWithObjectsAndKeys:
        [NSNumber numberWithInt:120], @"Delay",
        [NSNumber numberWithInt:100], @"Volume",
       nil];
[arr addObject:dic];

dic = [NSDictionary dictionaryWithObjectsAndKeys:
       [NSNumber numberWithInt:160], @"Delay",
       [NSNumber numberWithInt:100], @"Volume",
       nil];
[arr addObject:dic];

dic = [NSDictionary dictionaryWithObjectsAndKeys:
       [NSNumber numberWithInt:100], @"Delay",
       [NSNumber numberWithInt:100], @"Volume",
       nil];
[arr addObject:dic];

NSSortDescriptor *sortDesc = [[NSSortDescriptor alloc] initWithKey:@"Delay" ascending:YES];
[arr sortUsingDescriptors:[NSArray arrayWithObject:sortDesc]];

来源：https://stackoverflow.com/questions/10887490/sorting-mutable-array-by-dictionary-key

标签

iphone

objective-c

ios

sorting

nsmutablearray