API.md

API

createLoader(pattern:string|object|function, loaderDescriptor: object, options: object)

This function create a new data loader from loaderDescriptor.

const exampleLoader = createLoader('ACTION_TYPE_REQUEST',{
  shouldFetch: (context) => {
    // ...
  },
  fetch: (context) => {
    // ...
  },
  loading: (context) => {
    // ...
  },
  success: (context, result) => {
  },
  error: (context, err) => {
    // ...
  }
}, {
  ttl: 10000,
  retryTimes: 3,
  retryWait: fixedWait(500),
})

When an action that matches pattern is dispatched, the created loader will start loading data.

pattern:string|object|function

(required)

pattern uses the following rules:

1. If the pattern is an object, action is matched by _.isEqual(action, pattern) with lodash.
2. If the pattern is a function, action is matched by pattern(action) === true.
3. Otherwise, action is matched by action.type === pattern.

loaderDescriptor: object

(required)

loaderDescriptor is an object contains several functions. It MAY contains the following keys:

• shouldFetch:function optional
• loading: function optional
• fetch: function required
• success: function required
• error: function required

shouldFetch(context:object)

(optional)

This function is called first. If it returns true, this data loader will do nothing.

fetch(context: object)

(required)

This function is used to fetch data. It is only called if shouldFetch() returns true.

success(context:object, result:any)

(required)

Must returns an action. Called whenever a value resolves.

error(context:object, err:any)

(required)

Must returns an action. Called whenever a value rejects.

loading(context:object)

(optional)

Must returns an action. Called before fetching data.

functions will be called in this order:

##### shouldFetch -> loading -> fetch -> success or error

About context:object

context usually contains

• dispatch,
• getState
• action
• (other variables provided by middleware)

dispatch and getState are functions of redux store.

action is original dispatched action. It usually contains parameters for fetching data.

You can use createDataLoaderMiddleware(loaders, args) to add extra objects to context.

options:object

(optional)

options provides following optional values:

1. ttl: Provides a value in millisecond to cache the loader in order to prevent duplicated requests. (default: 10000, n/a to server side applications)
2. retryTimes: Total try times when fetching failed. (default: 1)
3. retryWait: Wait stategy that sleeps before retrying: (default: fixedWait(0)), see wait-strategies.js for detail.

---

createDataLoaderMiddleware(loaders: Array, args: object)

Returns a redux middleware.

loaders:Array

(required)

An array of created data loaders.

args:object

(_optional)

All the args(key-value) will be added to context.

---

load(action: object)

Returns a Promise.

Wrap an action and returns a Promise that can be processed by dataLoaderMiddleware.