迭代时是否可以从 mutablearray 中删除字典? [英] Is it possible to delete dictionary from mutablearray while iterating?

问题描述

for (int i = 0; i< [optionDataArr count]; i++) {
    NSString *sName  = [[optionDataArr objectAtIndex:i] objectForKey:kOptionName];
    NSString *sPrice = [[optionDataArr objectAtIndex:i] objectForKey:kOptionExtraPrice];

    if (sName.length == 0  && sPrice.length == 0) {
          [optionDataArr removeObjectAtIndex:i];
    }  
}

假设 optionDataArr 包含一个没有值的字典，当上面的代码执行时，我收到:

Suppose optionDataArr contains a dictionary having no values and when above code executes i receive:

Terminating app due to uncaught exception 'NSRangeException', reason: '*** -[__NSArrayM objectAtIndex:]: index 0 beyond bounds for empty array'

推荐答案

使用普通的旧 for 循环时可以删除项目，而使用快速枚举时则不能.

You can remove items when using a plain old for loop, you cannot when using fast enumeration.

不过，您的代码有问题.当您删除第 n 个元素时，下一个元素将是第 (n+2) 个.您需要手动将索引减 1 以说明移动的元素.

Your code is buggy, though. When you delete the nth element, the next element will be (n+2)th. You need to manually decrement the index by one to account for the shifted elements.

还请记住，在这种情况下，您确实需要对循环中的数组长度进行实时"边界检查，而不仅仅是使用保存长度的临时变量(或者您需要将其递减为嗯).

Also keep in mind, that in this case you really need to do "real time" bounds checking of the array length in the loop, and not just use a temporary variable holding the length (or you need to decrement that one as well).

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