數組枚舉期間的應用程序崩潰

Question

此代碼有什麼問題？我得到

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

它的NSMutableArray，而不是NSArray的

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]; 

Answer 1

的問題是你枚舉過程中改變陣列。這是不行的。

請

Best way to remove from NSMutableArray while iterating?

閱讀選擇的答案所有你需要的是存在的。

Answer 2

您在迭代迭代時不能改變（更改）集合，因爲迭代器對象也需要更改。您應該將要刪除的對象添加到數組中，然後將其刪除。

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];