如何使用字符串值获取NSArray中对象的索引? [英] How do I get the index of an object in an NSArray using string value?

问题描述

我想获取NSMutableArray类别中的对象的索引.

I want to get the index of an object within the NSMutableArray of categories.

类别对象具有属性"category_title"，我希望能够通过传递category_title的值来获取索引.

The category object has an attribute "category_title" and I want to be able to get the index by passing the value of category_title.

我已经浏览了文档，找不到解决此问题的简单方法.

I have looked through the docs and can't find a simple way to go about this.

推荐答案

NSArray不保证您只能存储给定对象的一个​​副本，因此必须确保自己处理(或使用NSOrderedSet).

NSArray does not guarantee that you can only store one copy of a given object, so you have to make sure that you handle that yourself (or use NSOrderedSet).

也就是说，这里有几种方法.如果您的类别对象实现isEqual:来匹配category_title，则可以只使用-indexOfObject:.

That said, there are a couple approaches here. If your category objects implement isEqual: to match category_title, then you can just use -indexOfObject:.

如果您不能这样做(因为类别对象使用不同的相等性定义)，请使用-indexOfObjectPassingTest:.它需要一个块，您可以在其中进行任何您想定义测试"的测试-在这种情况下，测试category_title字符串相等性.

If you can't do that (because the category objects use a different definition of equality), use -indexOfObjectPassingTest:. It takes a block in which you can do whatever test you want to define your "test" - in this case, testing category_title string equality.

请注意，这些都是为NSArray声明的，因此，如果仅查看NSMutableArray标头/文档，就不会看到它们.

Note that these are all declared for NSArray, so you won't see them if you are only looking at the NSMutableArray header/documentation.

代码示例.这假定具有NSString属性categoryTitle的类CASCategory的对象(我不能让自己在ivar名称中加下划线:-):

Code sample. This assumes objects of class CASCategory with an NSString property categoryTitle (I can't bring myself to put underscores in an ivar name :-):

    CASCategory *cat1 = [[CASCategory alloc] init];
    [cat1 setCategoryTitle:@"foo"];
    CASCategory *cat2 = [[CASCategory alloc] init];
    [cat2 setCategoryTitle:@"bar"];
    CASCategory *cat3 = [[CASCategory alloc] init];
    [cat3 setCategoryTitle:@"baz"];

    NSMutableArray *array = [NSMutableArray arrayWithObjects:cat1, cat2, cat3, nil];
    [cat1 release];
    [cat2 release];
    [cat3 release];

    NSUInteger barIndex = [array indexOfObjectPassingTest:^BOOL(id obj, NSUInteger idx, BOOL *stop) {
        if ([[(CASCategory *)obj categoryTitle] isEqualToString:@"bar"]) {
            *stop = YES;
            return YES;
        }
        return NO;
    }];

    if (barIndex != NSNotFound) {
        NSLog(@"The title of category at index %lu is %@", barIndex, [[array objectAtIndex:barIndex] categoryTitle]);
    }
    else {
        NSLog(@"Not found");
    }

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