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?

Answer 1

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.