iOS ~ Dictionary 字典多层级时，修改子层里面的数

• 注意：

• 因为不确定 父层字典 里面的 exam 是否是 字典 Dictionary，所以这里需要 转换 一下Dictionary，再赋值给子字典“exam”的对象“ collectState”。

    NSDictionary *dataExamDic = self.dataExamDic;     
    NSMutableDictionary *dataMutableDic = [NSMutableDictionary dictionaryWithDictionary:dataExamDic];
    // 可变字典里面的子字典，不一定也是可变字典，所以再转一下可变的
   NSMutableDictionary *examMutableDic = [NSMutableDictionary dictionaryWithDictionary:dataMutableDic[@"exam"]];
   [examMutableDic setObject:@"0" forKey:@"collectState"];
   // 在逐级添加回来：
    [dataMutableDic setObject:examMutableDic forKey:@"exam"];
    self.dataExamDic = [NSDictionary dictionaryWithDictionary:dataMutableDic];

示例：

(lldb) po self.dataExamDic
{
    answertState =     {
        answer = "";
        result = 0;
    };
    exam =     {
        aItem = "\U041f\U0440\U0435\U043f\U043e\U0434\U0430\U0432\U0430\U0442\U0435\U043b\U044c.";
        analysisText = "";
        collectState = 1;
        "exam_question_type" = 1;
        result = "<null>";
        resultModelEssay = "";
        rightResult = b;
        translateText = "";
        userAnswer = "<null>";
        uuid = 0b4b60d025b5442390e7489f49be5c49;
    };
    "record_uuid" = 4bf222c48b124bd5be1fd1f4c74037be;
    state = 1;
    type = 1;
}

(lldb)