React Entities Schema

React Entities Schema is an add-on to React Entities that performs runtime type checking on your app state using PropTypes.

Setup

To install:

npm install react-entities-schema

You also need to install React Entities and PropTypes, if you haven't done so yet:

npm install react-entities
npm install prop-types

Getting Started

This documentation assumes that you are already familiar with React Entities and the concepts of creating and using entities. You can find its documentation here.

React Entities Schema extends the React Entities library by enforcing structure to your entities using schema. It uses the PropTypes library to perform the schema-based runtime type checking on entities. You can refer to the PropTypes official documentation here

The type checking happens on every call to an entity's setState(). If the new state does not conform to the schema, a warning will be logged in the console (but no exception will be thrown). Because it uses PropTypes, type checking is only performed on non-production builds. This prevents any performance impact to production builds.

Creating Structured Entities

When creating a structured entity, we use the same format for defining a regular entity but we add a mandatory field called schema.

  import { T } from 'react-entities-schema';
 
  export const initialState = {
    value: 0
  };
 
  export const schema = {
    value: T.number.isRequired
  };
 
  export const increment = counter => by => {
    counter.setState({ value: counter.state.value + by });
  };
 
  export const decrement = counter => by => {
    counter.setState({ value: counter.state.value - by });
  };

Defining the schema

The format for defining the schema is exactly the same as defining a component's PropTypes, except that you need to use the wrapper called T from React Entities Schema. Do not use PropTypes directly for defining schema.

Note that unlike a React component's PropTypes, the top-level structure of the schema is strict, i.e. any prop key that is not defined in the schema will fail the type checking. For example, if the schema is:

  export const schema = {
    value: T.number.isRequired
  };

then setState({ wasReset: true }) will fail type checking because wasReset is not defined in the schema.

Automatically generating the initial state

Because the state of the structured entity has to strictly conform to the schema at all times, a valid initial state value is automatically generated, based on the schema, if an initialState value is not found in the entity definition.

Schema props that are not indicated as isRequired will always get an initial value of null, while those with isRequired will follow this initial-value table of common prop types:

Type	Default Value
T.string.isRequired	''
T.number.isRequired	0
T.bool.isRequired	false
T.array.isRequired	[]
T.object.isRequired	{}
T.func.isRequired	() => {}
T.instanceOf(C).isRequired	new C()
T.oneOf([1, 2, 3]).isRequired	1
T.oneOfType([T.number, T.string]).isRequired	0
T.any.isRequired	''

Both T.shape().isRequired and T.strict().isRequired will get an initial value of an object with its props getting default values based on the table above.

Naming the entity (optional)

A name value can be included in the structured entity definition. This is purely optional as it is only used to identify the entity on console warnings.

This is a typical structured entity format, with the optional name and implicit initial state:

entities/counter.js

  import { T } from 'react-entities-schema';
 
  export const name = 'counter';
 
  export const schema = {
    value: T.number.isRequired
  };
 
  export const increment = counter => by => {
    counter.setState({ value: counter.state.value + by });
  };
 
  export const decrement = counter => by => {
    counter.setState({ value: counter.state.value - by });
  };

Creating Structured Entity Hooks

For structured entities we need to use makeEntityWithSchema instead of the usual makeEntity function.

entities/index.js

import { makeEntityWithSchema } from 'react-entities-schema';
import * as counter from './counter';
 
export const useCounter = makeEntityWithSchema(counter);

This also supports all features of makeEntity including dependency injection, as detailed in the React Entities documentation.

Using Structured Entity Hooks in Components

A structured entity hook is used and behaves in the same way as a regular entity hook. All recipes in the React Entities documentation also apply to structured entities.