data-source-type-checking.md

Data source with type checking

tcomb - is a library for Node.js and the browser which allows you to check the types of JavaScript values at runtime with a simple and concise syntax. It's great for Domain Driven Design and for adding safety to your internal code.

Using tcomb we could check api input and output data in realtime and disable it for production env.

import DataSource from 'bivrost/data/source';
import tcomb from 'tcomb';

class UserDataSource extends DataSource {
  static steps = ['input', 'api', 'output'];

  static input = {
    user: tcomb.struct({
      id: tcomb.Number,
    }),
  };

  static output = {
    user: tcomb.struct({
      id: tcomb.Number,
      name: tcomb.String,
      lastname: tcomb.maybe(tcomb.String),
    }),
  };

  static api = {
    user: api('GET /user/:id'),
  };

  loadUser({ id }) {
    return this.invoke('user', {
      id,
    });
  }
}

const usersDataSource = new UserDataSource();

// OK
usersDataSource.loadUser({
  id: 1,
});

// Throw exception that ID attribute must be a Number.
usersDataSource.loadUser({
  id: '1',
});