C + + Library---JSON

The C + + operation JSON requires a separate library file, rather than directly $data = Array () as PHP does.

So the first to download the C + + JSON library file, and then the syntax to be respectful to the implementation of C + + JSON additions and deletions and other operations.

1. Add a JSON

Json::value root    // New JSON data the type of root,root can be int, string, obj, array ...

2. Adding data in JSON

 root.append (12345  ); Output: [12345]root[  key  Span style= "color: #800000;" > "].append ("  this is routine array in key     ); //  add a regular array, output: {"key": [This is routine array in key]}  root[   Key  ]="   Add a relation array   " //  add associative array, output: {"key": "Add a Relation array"}  

3. Json->string (write converts JSON value to string)

Jsoncpp in the Json::write is a pure virtual class, can not be used directly, only call his subclass, Json::fastwrite (normal output) and Json::stylewrite (formatted output)

Json::value admin;admin["Admin_key"]=555; Json::fastwriter Fast_write;cout<<fast_write.write (Admin) <<Endl;//output: {"Admin_key": 555}Json::value admin;admin["Admin_key"]=555; Json::stylewriter Style_write;cout<<style_write.write (Admin) <<Endl;//Output://{//"Admin_key": 555//}

4. String->json (read writes string to JSON value)

json::value root;std:: string " {\ "key\": \ "This is Value\"} " ; Json::reader Reader;reader.parse (abc,root); Json::styledwriter Style_write;

Note: If there is no key in the JSON array, but the key is accidentally used (called), the system will automatically add a key:null

json::value admin;admin["admin_key"]=555; int bbb = admin["key"].asint ();    // output Admin with the following result: {"Admin_key": 555, "key": null}

So when you use key, you must determine whether the key exists

 if  (Root.ismember ( " key  ) {//  There is no  cout<< exist  Span style= "color: #800000;" > " <<ENDL;}  else  {cout  << " no-exist   <<endl;}  

if (!root["key"].isnull ())       // judgment exists No, does not exist automatically creates a {    cout<<"exist"<<Endl;} Else {    cout<<"no-exist but I'll create one,the value is null"< <Endl;}    

C + + Library---JSON