JTOC: JSON to CPP Generator Tool

This is a custom cpp code generator I intend to use for my platformer game.

Purpose

Games usually have a lot of parameters and it should be comfortable to use json schemas to keep them. This tool should help me with this.

The main purpose is a development of this game. I recently decided that it's time to introduce json configs with constants because it's too much for me to recompile the game after changing any constant. Sometimes I wish to test the behaviour of units with different parameters. I also want to have one function FromJson(...) which will parse the whole config into object so this object (not the rapidjson::document) will be accessed in the application.

This way I expect to have the autocompletion hints, no additional typecasts and searches in dictionaries, no additional checks whether the field exist or not, etc. It's a great help in development proccess.

Another purpose is to play with python.

Features

It generates:

• classes
• object parser functions: FromJson(const rapidjson::Value&, T& object)

Target cpp standard: c++11 or higher

Restrictions

Types

It's now only support several simple types:

self.methods_by_type = {
  'bool': 'GetBool()', 
  'float': 'GetFloat()', 
  'int': 'GetInt()', 
  'std::string': 'GetString()'}

It also can generate arrays like std::array<T, Size> if T is a simple type from above.

Array of custom (user-defined) types is also supported but has strict restriction. All subobjects of the same array MUST have the same structure i.e, all their keys are SAME (so they can be converted to the objects of the same type). Of course values can be different. See example below.

Snippet taken from here

{
  "menu": {  
    "id": "file",  
    "value": "File",  
    "popup": {  
      "menuitem": [  
        { "value": "New", "onclick": "CreateDoc()"},  
        { "value": "Open", "onclick": "OpenDoc()"},  
        { "value": "Save", "onclick": "SaveDoc()"}  
      ]  
    }  
  }
}  

Cpp generator can handle now this type of schemas:

struct Menuitem {
  std::string value;
  std::string onclick;
};

struct Popup {
  std::array<Menuitem, 3> menuitem;
};

struct Menu {
  std::string id;
  std::string value;
  Popup popup;
};

You can see more detailed output here

Names

Naming conventions? Thrown away... Now it supports JSON SCHEMA with snake_case_without_capitals. These types and variables will be converted to CamelCase with uppercase first letter for class name and camelCaseVariables for other variables/data members.
Obviously ACRONYMS not supported.

Toolchain

• Python3

Run

Provide input and output file names like in the example

$ ls
external/  gen.py  LICENSE  README.md  res/
$ py gen.py -h
usage: gen.py [-h] [-i INPUT] [-o OUTPUT]

Generate a c++ file from the json schema

optional arguments:
  -h, --help            show this help message and exit
  -i INPUT, --input INPUT
                        path to json schema
  -o OUTPUT, --output OUTPUT
                        c++ file which will be generated from json schema
$ py gen.py -i res/example_0.json -o res/example_0.hpp