Sorting array with three different sorting options

Question

I have data collection(NSArray) of NSDictionary. Now in the app i need to show that data in three different sorting order. Now I do not want to make 3 different array (one for each sorting order with complete data) because it will consume memory nor I want to re-sort main array each time when user change sorting option. so now my problem is, I want a mechanism that I can only get indexes of main array in 3 different array(or any other datatype) in 3 different sorting order. Should I have to do this manually or is there a build in method for geting sorted index array from main array?

Why don't want to sort main array each time user changes the sort Order? — Anupdas
– Anupdas, Commented May 2, 2013 at 7:49
I think this computation would be very minimal and you are making a straight forward sorting more complex. Do profiling, if it's a real issue, then look for other ways to optimize this. — Anupdas
– Anupdas, Commented May 2, 2013 at 11:23

Eli Ganem · Accepted Answer · 2013-05-02 07:29:24Z

1

What you're asking is impossible. You want to have your items sorted in 3 different orders without saving them into different arrays AND without sorting them every time the sorting method changes.

You can't get it for free. You can pay either with memory or with performance. I'd go for memory, since it's not as costly as you think. Only the pointers to the NSDictionaries are kept in your array, so it shouldn't take too much memory.

answered May 2, 2013 at 7:29

Eli Ganem

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1 Comment

aLevelOfIndirection Over a year ago

I would like to add that unless you are sorting tens of thousands of objects, sorting takes hardly any time at all. You are better off sorting the array each time the user requests a change in the sort order.

karim · Accepted Answer · 2013-05-02 07:50:12Z

0

NSArray takes only objects as its elements. And objects pointers are stored in the array. So I guess, the option you are talking about, saving indexes in another array is something similar like saving pointers in sorting order. So, you have create 3 different arrays with the pointers to objects in a particular order, it will be the same, not taking more memory. When you copy the sorted objects in new arrays, the objects will not be allocated again, only their pointers will be stored. However you have to do the sorting in right way.

answered May 2, 2013 at 7:50

karim

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Comments

Monolo · Accepted Answer · 2013-05-02 08:49:26Z

If you want to keep your data in a single array, then you can use an NSMutableArray and (re-)sort it whenever the sort criteria changes.

Notice however that this means that if your data array is part of your model, and your sorting order is a presentation (UI) issue, then you are effectively mixing model, view and controller functionality in one object. Bad ( :-) ) but not the first time it has happened in history.

Here is an example using sort descriptors directly on keys of your dictionaries:

NSMutableArray *data = // ... your data as a mutable array

NSString* sortKey = // ... one of the 3 dictionary keys that you wish to sort by

NSSortDescriptor *sd = [NSSortDescriptor sortDescriptorWithKey:sortKey ascending:YES];

[data sortUsingDescriptors:@[sd]];

The data array is now sorted without using an extra array variable.

Dipen Panchasara · Accepted Answer · 2013-05-02 08:51:00Z

Step1 : Declare Enum Definition before import statement

enum COMP_TYPE {
    LOCALIZE_COMPARE = 1,
    CASE_INSENSITIVE = 2,
    LOCALIZE_CASE_INSENSITIVE = 3
    };

Step2 : Define following function in your .m file

-(NSArray *)sortArray:(NSArray *)arr WithType:(int)type andKey:(NSString *)key andOrder:(BOOL)order
{
    SEL _compareSelector;
    switch (type) {
        case LOCALIZE_COMPARE:
            _compareSelector = @selector(localizedCompare:);
            break;
        case CASE_INSENSITIVE:
            _compareSelector = @selector(caseInsensitiveCompare:);
            break;
        case LOCALIZE_CASE_INSENSITIVE:
            _compareSelector = @selector(localizedCaseInsensitiveCompare:);
            break;

        default:
            break;
    }
     NSSortDescriptor* sortDescriptor = [NSSortDescriptor sortDescriptorWithKey:key ascending:order selector:_compareSelector];
    return [arr sortedArrayUsingDescriptors:[NSArray arrayWithObject:sortDescriptor]];
}

Step3 : Declare your Array of Dictionary

NSArray *myArr = [NSArray arrayWithObjects:[NSDictionary dictionaryWithObjectsAndKeys:@"stack", @"name",
                                   @"goa", @"name1",nil],
         [NSDictionary dictionaryWithObjectsAndKeys:@"stack", @"name",
          @"goa", @"name1",nil],
         [NSDictionary dictionaryWithObjectsAndKeys:@"objective", @"name",
          @"c++", @"name1",nil], nil];

Step4 : call function with diferent Parameter

NSLog(@"%@",[self sortArray:myArr WithType:LOCALIZE_COMPARE andKey:@"name" andOrder:YES]);
NSLog(@"%@",[self sortArray:myArr WithType:CASE_INSENSITIVE andKey:@"name" andOrder:YES]);
NSLog(@"%@",[self sortArray:myArr WithType:LOCALIZE_CASE_INSENSITIVE andKey:@"name" andOrder:YES]);

Regexident · Accepted Answer · 2013-05-02 10:26:50Z

0

It is not possible to sort the same array for different orders.
You need to save the array each time before sorting.

edited May 2, 2013 at 10:26

Regexident

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answered May 2, 2013 at 7:35

Suraj Gupta

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