IOS 中会发生crash的操作

对字典和数组进行下列操作时会产生crash：

对于字典来说：

查询时，key=nil 或者 key=null 时都能正常运行

插入时，，key=nil 或者 key=null 都会crash

对于数组来说

index越界会crash

添加对象为nil时会crash

    NSDictionary *dic = @{@"key":@"value"};

    NSString *value = [dic objectForKey:nil];

    value = [dic objectForKey:[NSNull null]];

    NSMutableDictionary *mutDic = [dic copy];

    value = [mutDic objectForKey:nil];

    value = [mutDic objectForKey:[NSNull null]];

    

    value = [mutDic objectForKey:[NSNull null]];

    

    //    [mutDic setObject:@"123" forKey:nil];crash

    //    [mutDic setObject:nil forKey:@"123"];crash

    //    [mutDic setObject:[NSNull null] forKey:@"key"];crash

    //    [mutDic setObject:@"value" forKey:[NSNull null]];crash

    

//    [mutDic removeObjectForKey:nil]; //crash

//    [mutDic removeObjectForKey:[NSNull null]];//crash

//

    NSArray *arr = @[@(1),@(2),@(3)];

//    value = [arr objectAtIndex:4];//crash

    NSMutableArray *mutArr = [arr mutableCopy];

    

//    [mutArr insertObject:@(5) atIndex:5];//crash

//    [mutArr removeObjectAtIndex:5]; //crash

//    [mutArr replaceObjectAtIndex:5 withObject:@"5"];//crash

//    [mutArr insertObject:nil atIndex:0]; //crash

    

    [mutArr insertObject:[NSNull null] atIndex:0];

    [mutArr replaceObjectAtIndex:0 withObject:[NSNull null]];