JsonCpp经典入门

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1.JsonCpp

1.1.JsonCpp简介

JSON is a lightweight data-interchange format. It can represent numbers, strings, ordered sequences of values, and collections of name/value pairs.

JsonCpp is a C++ library that allows manipulating JSON values, including serialization and deserialization to and from strings. It can also preserve existing comment in unserialization/serialization steps, making it a convenient format to store user input files.

1.2.JsonCpp环境搭建

1.2.1.下载地址

https://github.com/open-source-parsers/jsoncpp#generating-amalgamated-source-and-header

1.2.2.Qt中JsonCpp安装

①　解压jsoncpp-master.zip包
②　在根目录下，运行python amalgamate.py
③　在根目录中生成dist文件夹包含三个文件dist/json/json-forwards.h dist/json/json.h dist/json.cpp
④　在Qt工程目录下，生成json文件夹，并拷贝json目录下。
⑤　在Qt工程中添加现有文件即可。

1.3.读写JsonCpp

1.3.1.写

#include <iostream>#include <fstream>#include "json/json.h"using namespace Json;using namespace std;#if 0{    "animals":{    "dog":[        {            "name":"Rufus",            "age":15        },        {            "name":"Marty",            "age":null        }        ]    }}#endifvoid writeJson(){    Value  rootAnimalsObj;    Value dog;    Value  dogArray;    Value  dogValueItem1;    dogValueItem1["name"] = "Rufus";    dogValueItem1["age"]  = 15;    Value  dogValueItem2;    dogValueItem2["name"] = "Marty";    dogValueItem2["age"]  = "";    dogArray.append(dogValueItem1);    dogArray.append(dogValueItem2);    dog["dog"] = dogArray;    rootAnimalsObj["animals"] = dog;    string str = rootAnimalsObj.toStyledString();    cout<<str;    ofstream ofs;    ofs.open("test_write.json");    ofs << str;    ofs.close();    return;}int main(){    writeJson();    return 0;}

1.3.2.读

#include <iostream>#include <fstream>#include "json/json.h"using namespace Json;using namespace std;#if 0{    "animals":{    "dog":[        {            "name":"Rufus",            "age":15        },        {            "name":"Marty",            "age":null        }        ]    }}#endifvoid readJson(){    ifstream is("aa.json");    if(!is)    {        cout<<"open error"<<endl;        return;    }    Reader reader;    Value root;    if(reader.parse(is,root))    {        cout<<root<<endl;        Value & dogArr = root["animals"]["dog"];        for(int i=0; i<dogArr.size(); i++)        {            cout<<dogArr[i]["name"].asString()<<endl;            cout<<dogArr[i]["age"].asInt()<<endl;        }    }    is.close();}int main(){    readJson();    return 0;}

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