@appnest/typed-actions
A lightweight library to create and type check flux/redux actions in typescript
Last updated a year ago by runebm .
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@appnest/typed-actions

What is this?

typed-actions is a lightweight library to create and type check flux/redux actions in typescript.

The library doesn't come with a dispatcher, its only purpose is to type check actions.

:fire: Features

:sparkles: Type magic - Define actions with the least amount of work on your side.

:mag: Small - No dependencies. Gzipped size: 483 B.

:vertical_traffic_light: Built in status - All statuses come with either a START, SUCCESS or FAILURE status. This removes boilerplate for asynchronous action dispatching.

:sparkles: Type Magic

Using this library you avoid keeping track of uncomfortable many boilerplate interfaces in order to type check actions in typescript. Read the section without this library to see what typing hell you avoid.

This is based the following Typescript features, including features from 3.0: type guards, conditional types, union types, generic rest parameters and optional elements in tuple types.

:vertical_traffic_light: Built in status

All actions created using this library comes with a status. This status can be either START, SUCCESS or FAILURE. All actions must have a status because this become very handy when creating actions in an asynchronous flow. This way you avoid a lot of boilerplate (see without this library)

Example

Let's start with a general example of how you would use this library.

Here we use an async action creator. You only need to define this action creator once for a given action, then it can be used to easily create and typecheck actions with different statuses: START, SUCCESS and FAILURE. This is done using the methods start, success and failure on the async action creator.

import { defaultAsyncActionCreator, isAction, Action } from "@appnest/typed-actions";

// 1: Make an action creator
const listUsers = defaultAsyncActionCreator<string[]>("LIST_USERS");

// 2: Create an action
const action = listUsers.success(["John", "Jane"]);
// { type: "LIST_USERS/SUCCESS", payload: ["John", "Jane"], id: "LIST_USERS", status: "SUCCESS" }

// 3: Dispatch the action any way you like

// 4: Handle the action in a store
function handler (action: Action) {

  if (isAction(action, listUsers.success)) {
    // Payload is type of "string[]" in this scope.
    console.log(action.payload.join(", "));

  } else if (isAction(action, listUsers.failure)) {
    // Payload is type of "Error" in this scope.
    console.log(`Something went wrong: ${action.payload.message}`)
  }

}

Walkhrough

Step 1: Make an action creator

In order to generate type safe actions you will first need to make an action creator. actionCreator takes a generic parameter that becomes the type of the action payload.

import { actionCreator } from "@appnest/typed-actions";

const sendMsg = actionCreator<string>("SENG_MSG_ACTION");

Step 2: Create the action

The action creator can now be used to create actions with a payload of the specified type.

const action = sendMsg("Hello World");

Here's the content of this action.

{ 
  type: "MY_ACTION/SUCCESS",
  id: "MY_ACTION",
  status: "SUCCESS",
  payload: "Hello World",
  meta: undefined
}

You will notice that the status is "SUCCESS". All actions must have a status becauses this become very handy when spawning actions in an asynchronous flow. "SUCCESS" is the default status.

Step 3: Dispatch the action

The action can be dispatched any way you like (for example redux store.dispatch(action)). This library is only build for creating and typechecking actions, not for dispatching them.

Step 4: Handle the action

Now you are ready to check the action type. This is done using the isAction function.

import { isAction, Action } from "@appnest/typed-actions";

function handler (action: Action) {

  // Check if "action" is of type "sendMsg"
  if (isAction(action, sendMsg)) {

    // Type of "payload" is "string" in this scope
    console.log(action.payload); 

  }

}

Without this library

Here is an example of what you would have to do if you did not use this library. Typed actions are achieved using discriminated unions. In addition it's difficult to automate dispatching eg. failure actions because the status is baked into the type.

// 1: Make a bunch of interfaces
interface ListUserStartAction {
  type: "LIST_USER/START";
}

interface ListUserSuccessAction {
  type: "LIST_USER/SUCCESS";
  payload: string[];
}

interface ListUserFailureAction {
  type: "LIST_USER/FAILURE";
  payload: Error;
}

type Action = ListUserStartAction | ListUserSuccessAction | ListUserFailureAction;

// 2: Create an action
const action: Action = {
  type: "LIST_USER/SUCCESS",
  payload: ["John", "Jane"]
};

// 3: Dispatch the action

// 4: Handle the action
function handler (action: Action) {
  switch (action.type) {

    case "LIST_USER/SUCCESS":
      // Payload is type of "string[]" in this scope.
      console.log(action.payload.join(", "));
      break;

    case "LIST_USER/FAILURE":
      // Payload is type of "Error" in this scope.
      console.log(`Something went wrong: ${action.payload.message}`);
      break;
  }
}

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