iphone - NSMutableArray 不是替换对象吗？

Question

我想替换NSMutableArrayobect 中的数组对象。我正在获取oldArray并_alertsArray改变它的价值，并想oldArray用newArray. 但是没有效果！！

NSArray *oldArray = (NSArray *)[_alertsArray objectAtIndex:[indexPath row]];
NSMutableArray *newArray = [[NSMutableArray alloc] initWithArray:oldArray copyItems:YES];
[newArray replaceObjectAtIndex:3 withObject:@"YES"];
[_alertsArray replaceObjectAtIndex:[indexPath row] withObject:newArray];

Answer 1

NSMutableArray *newArray = [_alertsArray mutableCopy];
[newArray replaceObjectAtIndex:3 withObject:@"YES"];
_alertsArray = newArray;