jsontool

Header-only C++ JSON library.

Overview

jsontool provides a simple API for producing and consuming JSON data:

• jsontool::var: a variant class representing a piece of JSON data.
• jsontool::parse: convert a JSON string to a jsontool::var.
• jsontool::stringify: convert a jsontool::var to a JSON string.

Usage

• Consuming JSON data
  • Parsing JSON
  • Operators
  • Type checking
  • Iteration
• Producing JSON data

Consuming JSON data

Parsing JSON

Use the parse function to create a var object from a string. Access its members using subscript notation (square brackets).

#include "jsontool.h"
// ...
std::string json = "[1, true, \"three\"]";  // some test data
jsontool::var data = jsontool::parse(json); // parse it
cout << data[2] << endl;                    // output: three

Operators

Assignment, cast and comparison operators behave as closely as possible to standard ECMA-262, edition 5. For example, objects and arrays are copied by reference, while primitives are copied by value. The == operator uses the abstract comparison algorithm, so 0 is equal to false, 1 is equal to true, 33 is equal to "33", and so on.

Type checking

The var class exposes the following methods to check the internal data type:

inline bool isUndefined();
inline bool isNull();
inline bool isBoolean();
inline bool isNumber();
inline bool isString();
inline bool isObject();
inline bool isArray();

Iteration

Internally, jsontool stores array data as vector<var> and object data as map<string, var>, and variants will cast to these types for member iteration.

using namespace std;
using namespace jsontool;

string json = "{ \"x\": 32.1, \"y\": 78.9 }";   // some test data
map<string, var> data = parse(json);            // parse it
map<string, var>::iterator i;                   // map iterator
for (i = data.begin(); i != data.end(); ++i) {  // iterate
    cout << i->first << endl;                   // output: x, y
    cout << i->second << endl;                  // output: 32.1, 78.9
}

jsontool::Array and jsontool::Object can be used as aliases for vector<var> and map<string, var>, respectively.

Producing JSON data

Use the stringify function to convert a var object to a JSON string.

using namespace std;
using namespace jsontool;

Object result;
string tags[] = { "good", "bad", "ugly" };

result["id"] = 32;
result["name"] = "Bob";
result["tags"] = tags;

cout << stringify(result) << endl;
// output: {"id":32,"name":"Bob","tags":["good","bad","ugly"]}

Most data types will convert to vars, including two dimensional arrays, which are interpreted as objects. The example above can be rewritten as:

using namespace std;
using namespace jsontool;

string tags[] = { "good", "bad", "ugly" };

var result[][2] = { 
    { "id", 32 }, 
    { "name", "Bob" }, 
    { "tags", tags } 
};

cout << stringify(result) << endl;
// output: {"id":32,"name":"Bob","tags":["good","bad","ugly"]}