在快速枚举中跟踪索引

Question

我想在使用快速枚举时得到当前对象的索引,即

for (MyClass *entry in savedArray) {
// What is the index of |entry| in |savedArray|?
}

Answer 1

查看NSArray的API ,您将看到该方法

- (void)enumerateObjectsUsingBlock:(void (^)(id obj, NSUInteger idx, BOOL *stop))block

所以试一试

[savedArray enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {

    //... Do your usual stuff here

    obj  // This is the current object
    idx  // This is the index of the current object
    stop // Set this to true if you want to stop

}];

Answer 2

我认为最直接的解决方案是简单地手动增加索引.

NSUInteger indexInSavedArray = 0;
for (MyClass *entry in savedArray) {
   indexInSavedArray++;
 }

或者,您可以不使用快速枚举.

    for (NSUInteger indexInSavedArray = 0; indexInSavedArray < savedArray.count; indexInSavedArray++) {
       [savedArray objectAtIndex:indexInSavedArray];
     }

Answer 3

这个问题已经得到解答了,但我想我会补充说,计数迭代实际上是iOS Developer Library文档中提到的技术:

NSArray *array = <#Get an array#>;
NSUInteger index = 0;

for (id element in array) {
    NSLog(@"Element at index %u is: %@", index, element);
    index++;
}

我确信会有一个奇特的伎俩,但我猜不是.:)