NSMutableArray没有正确地将数据存储到循环中

我尝试将一些NSMutableDictionaries存储到NSMutableArray抛出for循环：

 NSMutableArray *productsIdAndQuantities = [[NSMutableArray alloc]init]; NSMutableDictionary *element = [[NSMutableDictionary alloc]init]; for (id object in shoppingArray) { [element setObject:[object valueForKey:@"proId"] forKey:@"id"]; [element setObject:[object valueForKey:@"qty"] forKey:@"quantity"]; NSLog(@"%@",element);//tested, it's different on every iteration [productsIdAndQuantities addObject:element]; } 

循环结束后，我尝试调试productsIdAndQuantities ，刚出来它包含上面循环的项目的确切数量，但是有一个值。

这就是我的意思：

循环内部（ NSLog(@"%@",element); ）：

 { id = 13293; quantity = "-2"; } { id = 12632; quantity = "-5"; } 

循环之后（ NSLog(@"%@",productsIdAndQuantities);相同值!!!!!）：

 ( { id = 12632; quantity = "-5"; }, { id = 12632; quantity = "-5"; } ) 

Answer 1

您正在将相同的字典添加到数组中; 改为使用它，每次迭代都会分配一个新的字典：

 NSMutableArray *productsIdAndQuantities = [[NSMutableArray alloc]init]; for (id object in shoppingArray) { NSMutableDictionary *element = [[NSMutableDictionary alloc]init]; [element setObject:[object valueForKey:@"proId"] forKey:@"id"]; [element setObject:[object valueForKey:@"qty"] forKey:@"quantity"]; NSLog(@"%@",element);//tested, it's different on every iteration [productsIdAndQuantities addObject:element]; } 

注意：这假设您正在使用ARC，否则您将向右，左和中心泄漏词典…