__NSDictionaryI setObject：forKey：崩溃

Question

问题是我正在更改NSDictionary ，但是即使获取了mutableCopy ，应用程序也会崩溃。

以下是复制方法 ：

+ (NSMutableDictionary *)updateQuery:(NSMutableDictionary *)currentQuery toSearchAfterAccountPaginationSequence:(NSString *)accountPaginationSequence {

    //try1
    NSMutableDictionary *mutableQuery = [currentQuery mutableCopy];

    //try2 
    NSMutableDictionary *mutableQuery2=[NSMutableDictionary dictionaryWithDictionary:currentQuery];

    //crashes on this line
    mutableQuery[@"where"][@"account_pagination_sequence"] = @{ @"lt" : accountPaginationSequence };

    return mutableQuery;
}

错误日志（应用在数量有限的设备上崩溃）

[__NSDictionaryI setObject:forKey:]: unrecognized selector sent to instance

Answer 1

我认为这是您想要实现的目标

+ (NSMutableDictionary *)updateQuery:(NSMutableDictionary *)currentQuery toSearchAfterAccountPaginationSequence:(NSString *)accountPaginationSequence {

    //try1
    NSMutableDictionary *mutableQuery = currentQuery.mutableCopy;
    NSMutableDictionary *where =  mutableQuery[@"where"].mutableCopy;

    where[@"account_pagination_sequence"] = @{ @"lt" : accountPaginationSequence };
    mutableQuery[@"where"] =  where;

    return mutableQuery;
}

编辑：在Objective-C中，对对象调用mutableCopy不是递归的。您也需要在嵌套对象中调用mutableCopy。