spectract

Customize EOS smart contracts using JSON data compiled into C++ header files.

Prerequisites

Compiling JSON into C++ header requires only Python 3+.

Using C++ header with EOS smart contract requires only the eosiocpp compiler. There are essentially two ways to get eosiocpp available:

1. Download the code and build it, or
2. Pull an EOSIO Docker image which has eosiocpp contained within

Usage

./spectract.py <spec json input file> <output c++ header file>

The input JSON file must consist of a JSON object with each value being the variable name in C++, pointing to a JSON object describing value and type.

Example

Assume the following is contained in "data.json":

{
  "num": {
    "value": 42,
    "type": "uint8_t"
  },
  "str": {
    "value": "John Doe",
    "type": "std::string"
  },
  "float_": {
    "value": 3.1415,
    "type": "float"
  },
  "double_": {
    "value": 42.987654321,
    "type": "double"
  }
}

It is a breeze to compile into a C++ header "data.h":

% ./spectract.py data.json data.h

"data.h" now contains:

#ifndef SPECTRACT_DATA_H

namespace spectract {

struct data {
  const uint8_t num = 42;
  const std::string str = "John Doe";
  const float float_ = 3.1415;
  const double double_ = 42.987654321;
};

} // namespace spectract

#endif // SPECTRACT_DATA_H

Finally, in a smart contract the values can be accessed like:

spectract::data d;
printf("My name is %s\n", d.str);
// "My name is John Doe"