CODEWITHSUNDEEP
objective-cnssortdescriptor
some_id
some_id

Reputation: 29896

Sort descriptor on string returns unwanted result

I use this sort descriptor 

NSArray *sortedObjects = [self.array sortedArrayUsingDescriptors:[NSArray arrayWithObjects:[NSSortDescriptor sortDescriptorWithKey:@"index" ascending:YES], nil]];

The result is 10 and 11 are sorted alongside 1 and placed before 2.

index is 1/12
index is 10/12
index is 11/12  
index is 2/12  
index is 3/12
index is 4/12
index is 5/12
index is 8/12
index is 9/12

How can this be avoided?

Upvotes: 1

Views: 138

Answers (2)

Ramy Al Zuhouri
Ramy Al Zuhouri

Reputation: 22006

I don't know of that class are the items that you are printing, presumably strings. This happens because the '/' character has an higher value than '0'.

You have to use a custom method or block to make the comparison. So initialise also the selector, not only the key: 

NSSortDescriptor* sd= [[NSSortDescriptor alloc]initWithKey: @"index" ascending: YES selector: @selector(customCompare:)];
NSArray *sortedObjects = [self.array sortedArrayUsingDescriptors: @[ sd ] ];

In your customCompare: method you should compare the objects.

Upvotes: 0

zaph
zaph

Reputation: 112873

Use your own comparison with

- (NSArray *)sortedArrayWithOptions:(NSSortOptions)opts usingComparator:(NSComparator)cmptr

or
another sort that allows a custom comparator.

Then split up the days and compare the month and then the day.

Upvotes: 1

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