How can I convert an NSRange to a delimited string of its values?

Question

Given an NSRange, such as:

NSRange range = NSMakeRange(1, 22);

What's the best way to convert it to a comma-separated string of its values?

@"1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22"

The best I could come up with was to iterate over the range and insert its values into an NSArray, and then call -componentsJoinedByString: on the array. But that seems pretty wasteful, not to mention inelegant. Is there no better way?

@dasdom So you know where I'm coming from, eh? I'm used to it being easy: `perl -E 'say join ",", 1..22'` — theory, May 12 '14 at 18:57
`NSMutableString *string = [[NSMutableString alloc] init];for (int i = range.location; i < range.length; i ++){[string appendFormat:"%d,",i]};[string deleteCharactersInRange:NSMakeRange(string.length-1,1)];` ? That's the kind of thing your looking for? — Larme, May 12 '14 at 18:59
Well, usually that's not the role of a `NSRange`, I only used it in NSString actually, and we don't often use that (well, I didn't see a use)... If there is some logic, why not create it on the fly? You want element 3? `[NSString stringWithFormat:@"%d", 3+offsetStart]`. — Larme, May 12 '14 at 19:05
Similar/related: [Looping using NSRange](http://stackoverflow.com/q/8320987) (note wistful mention of Python there too!) — jscs, May 12 '14 at 21:05

score 2 · Answer 1 · edited May 12 '14 at 21:23

NSMutableString *string=[@"" mutableCopy];
for (int i = range.location; i<range.length-1; i++){
   [string appendFormat:@"%d,", i];
}
[string appendString@"%d", range.length-1];

If you want to hide the code, you can turn it into a function that would take the range and turn it into a string, that way this is hidden from your code. Or maybe turn it into a NSString class method, something like

[NSString stringWithRangeValues:range];

That would be like:

+ (NSString *)stringWithRangeValues:(NSRange)range{
        NSMutableString *string=[@"" mutableCopy];
        for (int i = range.location; i<range.lenght-1; i++){
           [string appendFormat:@"%d,", i];
        }
        [string appendString@"%d", range.length-1];
        return [NSString stringWithString:string];

}

yea i noticed it and removed it. – J2theC May 12 '14 at 19:01 — J2theC, May 12 '14 at 19:01

score 2 · Answer 2 · answered May 12 '14 at 19:09

2

My version using an array:

NSMutableArray *vals = [NSMutableArray arrayWithCapacity:range.length];
for (NSUInteger i = range.location; i < range.length; i++){
    [vals addObject:@(i)];
}
NSString *string = [vals componentsJoinedByString:@","];

answered May 12 '14 at 19:09

theory

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score 2 · Answer 3 · answered May 12 '14 at 19:20

2

You can use NSIndexSet with indexSetWithIndexesInRange: to generate a list of values, and then iterate through them with enumerateIndexesUsingBlock:. E.g.

NSIndexSet *indexSet = [NSIndexSet indexSetWithIndexesInRange:range];
NSMutableArray *indices = [NSMutableArray array];
[indexSet enumerateIndexesUsingBlock:^(NSUInteger i, BOOL *stop) {
    [indices addObject:@(i)];
}];
NSString *string = [indices componentsJoinedByString:","];

answered May 12 '14 at 19:20

Dan Loewenherz

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Maybe I should have asked for increasingly complex ways to solve this problem. ;-P – theory May 12 '14 at 20:03
Hah. It was all I could think of :) I thought there might have been a way to convert an NSIndexSet to an NSArray populated with the indices of the elements, but alas, no dice. NSIndexSet is basically the higher-level version of an NSRange so my answer doesn't quite have too much of a benefit, unless you want to stay away from using NSRange directly. – Dan Loewenherz May 12 '14 at 21:06

How can I convert an NSRange to a delimited string of its values?

3 Answers3