Sorting an nsarray of strings not string based

Question

So i have an array that i retrieve from a web service in no particular order

example:

0 => x large, 
1 => large, 
2 => XX large, 
3 => small,
4 => medium, 
5 => x small

I need to sort them: firstly based on specific - which could be reverse alphabetic:

small
medium
large

Secondly i need to sort them based on their 'x' counter parts:

x small
small
medium
large
x large
xx large

I know i can do this with brute force string matching but i would really like a suggestion on how to do this tidily, perhaps a regex or something more elegant?

Answer 1

Use NSComparator block syntax. Something like

NSArray * sizes = [NSArray arrayWithObjects:  @"x small",@"small",@"medium",@"large",@"x large", nil];

NSArray *sortedBySizes =[array sortedArrayUsingComparator:^NSComparisonResult(id obj1, id obj2) {
    if ([sizes indexOfObject:[obj1 size]]> [sizes indexOfObject:[obj2 size]])
        return (NSComparisonResult)NSOrderedAscending;
    if ([sizes indexOfObject:[obj1 size]]< [sizes indexOfObject:[obj2 size]])
        return (NSComparisonResult)NSOrderedDescending;
    return (NSComparisonResult)NSOrderedSame;
}];

---

In the second approach I added a mapping between the numbers send by the web server and the x-sizes. Now [obj size]; is suppose to return a NSNumber object.

NSArray * sizesStrings = [NSArray arrayWithObjects:  @"x small",@"small",
                                                     @"medium",@"large",
                                                     @"x large",@"xx large", 
                                                     nil];
NSArray * sizesNumbers = [NSArray arrayWithObjects:[NSNumber numberWithInt:5],
                                                   [NSNumber numberWithInt:3],
                                                   [NSNumber numberWithInt:4],
                                                   [NSNumber numberWithInt:1],
                                                   [NSNumber numberWithInt:0],
                                                   [NSNumber numberWithInt:2], 
                                                   nil];

NSDictionary *sizes = [NSDictionary dictionaryWithObjects:sizesStrings 
                                                   forKeys:sizesNumbers];

NSArray *sortedBySizes = [array sortedArrayUsingComparator:^NSComparisonResult(id obj1, id obj2) {
    NSString *sizeObj1String = [sizes objectForKey:[obj1 size]];
    NSString *sizeObj2String = [sizes objectForKey:[obj1 size]];

    int i1 = [sizesStrings indexOfObject:sizeObj1String];
    int i2 = [sizesStrings indexOfObject:sizeObj2String];

    if (i1 > i2)
        return (NSComparisonResult)NSOrderedAscending;
    if (i2 > i1)
        return (NSComparisonResult)NSOrderedDescending;
    return (NSComparisonResult)NSOrderedSame;
}];

---

The second task of the question — the grouping into small, medium, large — could be done like this:

NSDictionary *groups = [NSDictionary dictionaryWithObjects:[NSArray arrayWithObjects:[NSMutableArray array],[NSMutableArray array],[NSMutableArray array], nil] 
                                    forKeys:[NSArray arrayWithObjects:@"small",@"medium",@"large",nil]
                        ];
[array enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {
    int i = [[obj size] intValue];
    if (i == 5 || i == 3) 
        [[groups objectForKey:@"small"] addObject:obj];
    else if (i == 2 || i == 0 || i == 1)
        [[groups objectForKey:@"large"] addObject:obj];
    else
        [[groups objectForKey:@"medium"] addObject:obj];

}];

Answer 2

First, add a category to NSString for sanity's sake

@implementation NSString (NSStringContainsCategory)

- (BOOL)contains:(NSString*)string;
{
    if(IsEmpty(string)) {
        return NO;
    }

    NSRange range = [self rangeOfString:string options:NSCaseInsensitiveSearch];

    if (range.location != NSNotFound) {
        return YES;
    }

    return NO;
}

@end

Then,

NSMutableArray* sortMe = [NSMutableArray arrayWithArray:theArrayYouWantToSort];

NSComparator smlComparator = ^NSComparisonResult(id string1, id string2) {
    // 1 = small, 2 = medium, 3 = large        
    NSNumber* string1Number = [NSNumber numberWithInt:0];
    NSNumber* string2Number = [NSNumber numberWithInt:0];

    if([string1 contains:@"large"]) {
        string1Number = [NSNumber numberWithInt:3];
    } else if([string1 contains:@"medium"]) {
        string1Number = [NSNumber numberWithInt:2];
    } else if([string1 contains:@"small"]) {
        string1Number = [NSNumber numberWithInt:1];
    }

    if([string2 contains:@"large"]) {
        string2Number = [NSNumber numberWithInt:3];
    } else if([string2 contains:@"medium"]) {
        string2Number = [NSNumber numberWithInt:2];
    } else if([string2 contains:@"small"]) {
        string2Number = [NSNumber numberWithInt:1];
    }

    NSComparisonResult compareSml = [string1Number compare:string2Number];

    if(compareSml == 0) {
        // if they are the same size, just use normal string comparison to sort x xx xxx etc
        return [string1 compare:string2];
    }
    return compareSml;
};

[sortMe sortUsingComparator:smlComparator];

I wouldn't call it elegant, but it's the simplest answer I could think of. You may want to reverse the ordering to suit your needs - just apply negative to comparison result. Comment if this doesn't work out, and I'll give it another look.

Answer 3

maybe you can sort your strings where "xx s" was replaced by "z", "xs" was replaced by "v" and "xl" replaced with "b" and "xx l" with "a". q