state-model helps to define application state structure, default values and validate modifications. E.g. if app
state is too complex to remember it.

This is a es6 module. No compiled version is provided. Install via npm install state-model or yarn add state-model

API

• const sm = new StateModel(definition: Object) - create new state model instance. Definition has a specific format
• sm.set(state: Object, modifier: Object) => Object - validates modifier against definition, extends with default
  values if state doesn’t have them. Returns valid modifier or throws an error if modifier is invalid

Definition format

Every attribute of definition can have the following parameters:

• __type - required. Possible values: “*“ - any type; “string”; “array”; “number”; “object”; “null”; “boolean”
• __nullable - optional. If true, the attribute could have “null” value

• __value - optional. Used as default value of the attribute (if __type is not “object”). If __type is “object”,
  but doesn’t have default value, it will throw an error. To assign any object set __type: '*'

• PLANNED: __required - optional. Throw an error if modifier doesn’t contain required key

For example:

{
  // root object should always be of object type
  __type: 'object',
  __value: {
    'attr-1': {
      __type: '*',
      __value: {
        'attr-2': {
          __type: 'string',
          __nullable: true
        }
      }
    },
    'attr-3': {
      __type: '*',
    }
  }
}

How to use?

// In case you are using object-state-storage for state management
import StateModel from 'state-model';
const store = new ObjectStateStorage({ error: null });
// for example store contains a list of items
const sm = new StateModel({
  __type: 'object',
  __value: {
    '*': {
      __type: 'object',
      __value: {
        title: {
          __type: 'string',
        },
        timestamp: {
          __type: 'number',
        },
        display: {
          __type: 'boolean',
          __value: false,
        },
      },
    },
    error: {
      __type: 'string',
      __nullable: true,
      __value: null,
    },
  },
});
store.setState(state => sm.set(state, { id_1: { title: 'Hello world', timestamp: 1510737513759 } }));
// store.state is going to be
// {
//   id_1: { title: 'Hello world', timestamp: 1510737513759, display: false },
//   error: null,
// }
store.setState(state => {
  try {
    return sm.set(state, { id_1: { timestamp: '1510737513759' } });
  } catch (err) {
    return {
      error: err.toString(),
    };
  }
});
// store.state is going to be
// {
//   error: 'Error: Type mismatch at "id_1.timestamp" ("number" expected, but "string" received)',
//   id_1: { title: 'Hello world', timestamp: 1510737513759, display: false },
// }