NSPredicate而不是循环来过滤对象数组

Question

有人告诉我,我可以NSPredicate用来复制这种方法的结果

- (void) clearArrayOut
{
    bool goAgain = false;

    for (int j=0; j<[array count]; j++)
    {
        if ([[array objectAtIndex:j] someMethod] == NO)
        {
            [array removeObjectAtIndex:j];
            goAgain = true;
            break;
        }
    }

    if (goAgain) [self clearArrayOut];
}

如何NSPredicate根据自定义类调用的某些方法的结果来过滤数组？

Answer 1

要应用过滤器制作副本:

NSArray *filteredArray = [someArray filteredArrayUsingPredicate:
    [NSPredicate predicateWithBlock:^(id object, NSDictionary *bindings) {
        return [object someMethod]; // if someMethod returns YES, the object is kept
    }]];

要过滤NSMutableArray到位:

[someMutableArray filterUsingPredicate:
    [NSPredicate predicateWithBlock:^(id object, NSDictionary *bindings) {
        return [object someMethod]; // if someMethod returns YES, the object is kept
    }]];

但for如果我过滤一个小数组,我可能只会使用一个循环.但是,我会for以不同的方式编写我的循环,以避免不得不递减索引变量或递归调用自己:

- (void)clearArrayOut:(NSMutableArray *)array {
    for (int i = array.count - 1; i >= 0; --i) {
        if (![[array objectAtIndex:i] someMethod]) {
            [array removeObjectAtIndex:i];
        }
    }
}