iphone - 使用块从数组中获取子数组非常令人困惑

Question

我有一个对象数组（json 对象） 每个对象都具有以下性质：

{
        author = "<null>";
        category =         {
            "created_at" = "2011-02-06T18:11:39Z";
            id = 4;
            name = lawyers;
        };
        "created_at" = "<null>";
        id = 693;
        "mobile_user_id" = "<null>";
        "rating_count" = 0;
        status = 1;
        text = "A brain walks into a bar and says, \"I'll have a pint of beer please. \"The barman looks at him and says \"Sorry, I can't serve you.\" \"Why not?\" asks the brain. \"You're already out of your head.\"";
        title = "A brain goes to a local bar";
    }

从这些对象数组中，我想找到类别 id = 4 的对象并创建一个子数组。

有人可以帮助我使用块并从数组中获取子数组吗？

Answer 1

我想通过“使用块”，你的意思是使用 NSArray 的方法，例如

- (NSIndexSet *)indexesOfObjectsPassingTest:(BOOL (^)(id obj, NSUInteger idx, BOOL *stop))predicate

然后它看起来像

NSIndexSet *indexes = [yourArray indexesOfObjectsPassingTest:^(id obj, NSUInteger idx, BOOL *stop) {
    return (BOOL)([[obj valueForKeyPath:@"category.id"] intValue] == 4);
}];
NSArray *filteredArray = [yourArray objectsAtIndexes:indexes];

这就是你所要求的，但我宁愿使用 filteredArrayUsingPredicate: 像这样：

NSPredicate *pred = [NSPredicate predicateWithFormat:@"category.id = %@", [NSNumber numberWithInt:4]];
NSArray *filteredArray = [yourArray filteredArrayUsingPredicate:pred];