Objective-c：找到NSArray中元素的最后一个索引

Question

I have a NSArray, and I want to find the last occurrence of an element. For example:

[apple, oranges, pears, apple, bananas];
int i = lastIndexOf("apple");
out: i == 3;

I'm struggling to find a simple solution looking an the APIS, but there aren't example so it's pretty hard to understand which function I should use.

Answer 1

NSUInteger index = [array indexOfObjectWithOptions:NSEnumerationReverse
    passingTest:^(id obj, NSUInteger i, BOOL *stop) {
        return [@"apples" isEqualToString:obj];
    }];

If the array doesn't contain @"apples" , index will be NSNotFound .

Answer 2

NSArray has indexOfObjectWithOptions:passingTest: , this will allow you to search in reverse.

For example:

NSArray *myArr = @[@"apple", @"oranges", @"pears", @"apple", @"bananas"];
NSString *target = @"apple";

NSUInteger index = [myArr indexOfObjectWithOptions:NSEnumerationReverse
                                      passingTest:^BOOL(NSString *obj, NSUInteger idx, BOOL *stop) {
                                          return [target isEqualToString:obj];
                                      }];

You can find out more details of this method in the Documentation by Apple .

Answer 3

If anyone wants a reusable method with categories, I had written one for lastIndexOf.

Code can be found and freely used from here -

http://www.tejasshirodkar.com/blog/2013/06/nsarray-lastindexof-nsmutablearray-lastindexof/