How to sort NSArray of NSStrings using NSPredicate?

Question

I have NSarray contains the list of Animals. The array contains a list of animals with repeated elements. I have to make an array with distinct values in the array. Repeated values should be removed using NSPredicate .

Here is my Code :-

NSArray *arrAnimals = [[NSArray alloc] initWithObjects:@"Cat",@"Rat",@"Fish",@"Cat",@"Fish",@"Cat",@"Cat",@"Bird",@"Fish",@"Cat",@"Frog", nil];

NSPredicate *predicate = [NSPredicate predicateWithFormat:[NSString stringWithFormat:@"distinct"]];
arrAnimals = [arrAnimals filteredArrayUsingPredicate:predicate];

Here I am using "distinct" keyword for sorting the array, but not able to find any solution. I have preferred many links.

http://www.infragistics.com/community/blogs/stevez/archive/2013/10/21/ios-objective-c-filtering-a-nsarray-using-nspredicate.aspx

Please resolve my problem.

Answer 1

没有谓词，但是可以使用键值运算符：

distinct = [array valueForKeyPath:@"@distinctUnionOfObjects.self"];

Answer 2

You can remove duplicates from an array by creating a set with its objects and converting it back to an array.

NSArray *arrAnimals = [[NSArray alloc] initWithObjects:@"Cat",@"Rat",@"Fish",@"Cat",@"Fish",@"Cat",@"Cat",@"Bird",@"Fish",@"Cat",@"Frog", nil];
NSArray *arrayWithoutDuplicates = [[NSSet setWithArray:arrAnimals] allObjects];

Answer 3

try this one with answered by @iMartin

 NSArray *arrAnimals = @[@"Cat",@"Rat",@"Fish",@"Cat",@"Fish",@"Cat",@"Cat",@"Bird",@"Fish",@"Cat",@"Frog"];

    arrAnimals= [arrAnimals valueForKeyPath:@"@distinctUnionOfObjects.self"];

    arrAnimals= [arrAnimals sortedArrayUsingComparator:^NSComparisonResult(id obj1, id obj2) {
        unichar firstChar =  [obj1 characterAtIndex:0];
        unichar secondChar =  [obj2 characterAtIndex:0];

        if ( firstChar == secondChar) {
            return NSOrderedSame;
        } else {
            if ( firstChar > secondChar) {
                return NSOrderedDescending;
            } else {
                return NSOrderedAscending;
            }

        }

    }];