数组枚举期间应用崩溃 [英] App crash during array enumerating

问题描述

此代码有什么问题？我得到

What is wrong with this code ? I get

 Collection <NSCFArray: 0x101e1b6d0> was mutated while being enumerated

这是NSMutableArray，而不是NSArray

It is NSMutableArray, not NSArray

NSMutableArray *set = [[NSMutableArray alloc]initWithObjects:@"first", @"second", @"third", @"third", nil];

    [set enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop)
     {
         if([obj isEqualToString:@"third"])
         {
             [set removeObjectAtIndex:idx];
         }
     }];

    [pool drain];

推荐答案

您不能在（您正在迭代它，因为迭代器对象也需要更改。您应该将要删除的对象添加到数组中，然后再删除它们。

You can't mutate (change) a collection while you are iterating it because the iterator object would need to change too. You should add the objects you want to remove to an array and remove them afterwards.

NSMutableArray *set = [[NSMutableArray alloc]initWithObjects:@"first", @"second", @"third", @"third", nil];

NSMutableArray *arrayOfObjectsToRemove = [[NSMutableArray alloc] init];
[set enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop)
 {
     if([obj isEqualToString:@"third"])
     {
         [arrayOfObjectsToRemove addObject:obj];
     }
 }];

[set removeObjectsInArray:arrayOfObjectsToRemove];

[pool drain];

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