Objective-c: find the last index of an element in a NSArray

问题

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.

回答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.

回答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.

回答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/

来源：https://stackoverflow.com/questions/12940431/objective-c-find-the-last-index-of-an-element-in-a-nsarray

标签

objective-c

find

nsarray