Sorting a NSMutable Dictionary

Question

Any pointers for the right direction would be gratefully received,

I have a NSDictionary of the format:

{
3 = "special-collection-procedures-see-notes|";
13 = "<p>None Given</p>";
16 = "";
6 = "<p>Arrange for sample to be separated at an interim site and subsequently transport frozen to lab, if it cannot reach lab within one hour.</p>";
9 = "<p>Stored in laboratory at -20C</p>";
12 = "<p>None</p>";
2 = "images/tubes/lightblue_tube_large.png";
15 = "";
5 = "";
8 = "Up to 28 days";
11 = "<p>Some indications: Hereditary Angioedema</p><p>Sample type is citrated plasma though plain serum can also be used.</p>";
1 = " Functional C1 esterase inhibitor";
14 = "|";
4 = "5-10 mL";
7 = "<p>Frozen if unable to deliver within one hour</p>";
10 = "<p>expressed as a percentage of a control serum with 75% -125% being classed as normal.</p>";

}

Which I would like to sort the keys so that the order is:

1 = " Functional C1 esterase inhibitor";
2 = "images/tubes/lightblue_tube_large.png";

Etc.

I have this piece of code:

NSArray *myArray; 

myArray = [[valuesDictionary allKeys] sortedArrayUsingComparator: ^(id obj1, id obj2) {

    if ([obj1 integerValue] > [obj2 integerValue]) {

        return (NSComparisonResult)NSOrderedDescending;
    }
    if ([obj1 integerValue] < [obj2 integerValue]) {

        return (NSComparisonResult)NSOrderedAscending;
    }

    return (NSComparisonResult)NSOrderedSame;
}];

NSMutableDictionary *sortedDisplay = [[NSMutableDictionary alloc] init];

for (id object in myArray) {
    // do something with object
    [sortedDisplay setObject:[valuesDictionary objectForKey:object] forKey:object];

}

Which gives me a sorted myArray: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16

But the final "sorted" mutable dictionary is not sorted i.e its

Printing description of sortedDisplay:

{
13 = "<p>None Given</p>";
12 = "<p>None</p>";
11 = "<p>Some indications: Hereditary Angioedema</p><p>Sample type is citrated plasma though plain serum can also be used.</p>";
7 = "<p>Frozen if unable to deliver within one hour</p>";
6 = "<p>Arrange for sample to be separated at an interim site and subsequently transport frozen to lab, if it cannot reach lab within one hour.</p>";
2 = "images/tubes/lightblue_tube_large.png";
1 = " Functional C1 esterase inhibitor";
14 = "|";
15 = "";
10 = "<p>expressed as a percentage of a control serum with 75% -125% being classed as normal.</p>";
9 = "<p>Stored in laboratory at -20C</p>";
8 = "Up to 28 days";
5 = "";
4 = "5-10 mL";
3 = "special-collection-procedures-see-notes|";
16 = "";

}

What am I doing wrong?

Possible duplicate: http://stackoverflow.com/questions/376090 — mpontillo, Jul 13 '12 at 23:18
stackoverflow.com/questions/376090 does explore similar issues — Craig Webster, Jul 14 '12 at 14:50

score 3 · Answer 1 · answered Jul 13 '12 at 23:10

3

What am I doing wrong?

Trying to sort a dictionary.

answered Jul 13 '12 at 23:10

tommyo

531
4
10

Jesse Gumpo · Answer 2 · 2012-07-13T23:32:32.610

3

You're going to want to make a sorted array:

    NSArray *sortedKeys = [dictionary keysSortedByValueWithOptions:NSNumericSearch usingComparator:^NSComparisonResult(NSString *a, NSString *b){
        return [a compare:b];
    }];
    //Now you have an array of sorted keys


    NSMutableArray *sortedArray = [[NSMutableArray alloc] initWithCapacity:sortedKeys.count];
    for (NSString *key in sortedKeys){
        NSDictionary *dict = [NSDictionary dictionaryWithObject:[dictionary valueForKey:key] forKey:key];
        [sortedArray addObject:dict];
    }
    //Now you have a sortedArray of key-value pairs

edited Jul 13 '12 at 23:32

answered Jul 13 '12 at 23:26

Jesse Gumpo

4,777
1
20
29

Thanks, used this in the end NSEnumerator *sectEnum = [myArray objectEnumerator]; NSMutableArray *index = [[NSMutableArray alloc] init]; id sKey; while((sKey = [sectEnum nextObject])) { if ([valuesDictionary objectForKey:sKey] != nil ) { [index addObject:[valuesDictionary objectForKey:sKey] ]; } } – Craig Webster Jul 14 '12 at 14:51

score 2 · Accepted Answer · answered Jul 13 '12 at 23:16

2

Tommyo is right, you can't sort a NSDictionary. Its purpose is to store and retrieve data efficiently in terms of performance.

If you need to store data in a particular order, use an NSArray for the keys (as you are already doing), and use it to access the dictionary values when you need them.

answered Jul 13 '12 at 23:16

Xavi Gil

11,460
4
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71

Thanks, was trying to provide a way of displaying the data in a sortable format for a table view. Probably on the wrong track! – Craig Webster Jul 13 '12 at 23:39

Sorting a NSMutable Dictionary

3 Answers3