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那么只需要用文件流把这个字符串送到一个string里
然后创建一个Document对象
再把string转成const char *类型以后送到rapidjson自带的函数Parse里处理就好了
我当时遇到的是这样的json字符串:
- {"info": {"description": "This is v1.0 of the VQA dataset.", "url": "http://visualqa.org", "version": "1.0", "year": 2015, "contributor": "VQA Team", "date_created": "2015-10-02 19:35:04"}, "task_type": "Open-Ended", "data_type": "mscoco", "license": {"url": "http://creativecommons.org/licenses/by/4.0/", "name": "Creative Commons Attribution 4.0 International License"}, "data_subtype": "val2014", "questions": [{"question": "What is the table made of?", "image_id": 350623, "question_id": 3506232}, {"question": "Is the food napping on the table?", "image_id": 350623, "question_id": 3506230}, {"question": "What has been upcycled to make lights?", "image_id": 350623, "question_id": 3506231}, {"question": "Is there water in the water bottle?", "image_id": 552610, "question_id": 5526102}]}
可以发现"questions"这个标签下其实是一个数组
所以就先利用
- Value & ques = d["questions"];
把questions标签下的内容都放到一个Value对象里面
可以利用rapidjson自带的ques.IsArray()来检测是不是数组
然后再遍历这个数组
利用v.HasMember("question")来检测是否带有这个标签,如果带有这个标签的话再利用v["question"].IsString()来检测是否是这个类型
都符合的话就用temp_ques = v["question"].GetString();把它抓取出来
另外的两个也同理
总的代码如下:
- #include <cstdio>
- #include <string>
- #include <iostream>
- #include <fstream>
- #include <vector>
- #include <tuple>
- #include "rapidjson/document.h"
- #include "rapidjson/prettywriter.h"
- #include "rapidjson/filereadstream.h"
- #include "rapidjson/filewritestream.h"
- #include "rapidjson/stringbuffer.h"
- using namespace std;
- using namespace rapidjson;
- void json_analysis(const string filename, vector<tuple<string, int, int>> &result)
- {
- ifstream json_file;
- json_file.open(filename.c_str());
- string json;
- if (!json_file.is_open())
- {
- cout << "Error opening file" << endl;
- exit(1);
- }
- getline(json_file, json);
- Document d;
- d.Parse<0>(json.c_str());
- Value & ques = d["questions"];
- string temp_ques;
- int temp_ima_id, temp_ques_id;
- if (ques.IsArray())
- {
- for (size_t i = 0; i < ques.Size(); ++i)
- {
- Value & v = ques[i];
- assert(v.IsObject());
- if (v.HasMember("question") && v["question"].IsString()) {
- temp_ques = v["question"].GetString();
- }
- if (v.HasMember("image_id") && v["image_id"].IsInt()) {
- temp_ima_id = v["image_id"].GetInt();
- }
- if (v.HasMember("question_id") && v["question_id"].IsInt()) {
- temp_ques_id = v["question_id"].GetInt();
- }
- auto temp = make_tuple(temp_ques, temp_ima_id, temp_ques_id);
- result.push_back(temp);
- }
- }
- /*
- for (size_t i = 0; i < result.size(); i++){
- cout << get<0>(result[i]) << endl;
- cout << get<1>(result[i]) << endl;
- cout << get<2>(result[i]) << endl;
- }
- return 0;
- */
- }