在自定义类上实现NSFastEnumeration

Question

我有一个继承自NSObject的类.它使用NSMutableArray来保存子对象,例如使用NSMutableArray*项的People来保存Person对象.如何在项目上实现NSFastEnumerator？

我尝试过以下但是无效:

@interface People : NSObject <NSFastEnumeration>
{
    NSMutableArray *items;
}

@implementation ...

- (NSUInteger)countByEnumeratingWithState:(NSFastEnumerationState *)state objects:(id *)stackbuf count:(NSUInteger)len
{
    if(state->state == 0)
    {
        state->mutationsPtr = (unsigned long *)self;
        state->itemsPtr = items;
        state->state = [items count];
        return count;
    }
    else
        return 0;
}

Answer 1

您没有正确使用NSFastEnumerationState结构.请参阅NSFastEnumeration Protocol Reference并查看常量部分以查看每个字段的说明.在你的情况下,你应该保持state->mutationsPtr为零.state->itemsPtr应该设置为对象的C数组,而不是NSArray或NSMutableArray.您还需要将相同的对象放入作为stackbuf传递的数组中.

但是,由于您使用NSMutableArray来包含要枚举的对象,因此您只需将调用转发给该对象:

- (NSUInteger)countByEnumeratingWithState:(NSFastEnumerationState *)state objects:(id *)stackbuf count:(NSUInteger)len {
    return [items countByEnumeratingWithState:state objects:stackbuf count:len];
}