Lightweight TypeScript RemoteData implementation
npm install @abraham/remotedataRead Slaying a UI Antipattern with Web Components (and TypeScript) for a more thorough guide.
This is an example class that gets a tweet (type Status) from a remote HTTP API.
import { Failure, fold, Initialized, Pending, RemoteData, Success } from '@abraham/remotedata';
import { Status } from 'twitter-d';
// Define what the RemoteData Failure and Success types will be.
type State = RemoteData<number, Status>;
class Thing {
// Set the initial state as Initialized.
private state: State = new Initialized();
constructor() {
// On instantiation start the remote call and render the current state.
this.getStatus();
this.render();
}
private async function getStatus() {
// Before starting the remote call set the current state to Pending.
this.state = new Pending();
// Perform the actual remote request.
const response = await fetch('https://api.example.com/tweet');
if (response.ok) {
// If the request succeeds set the state to Success with the returned data.
const status: Status = await response.json();
this.state = new Success(status);
} else {
// If the request does not succeed set the state to Failure with the reason.
this.state = new Failure(status_code);
}
// Render the new state.
this.render();
}
private get view(state: State): (state: State) => string {
// Use `fold` to easily define logic based on the current state.
// Fold takes four methods as parameters in the order of Initialized, Pending, Failure, and
// Success and returns a method that takes a `RemoteData` state instance as a parameter. When
// the returned method gets called with a `RemoteData` state, the method matching the correct
// state gets called.
return fold<string, number, Status>(
// What to do if the state is Initialized.
() => 'Initialized',
// What to do if the request is Pending.
() => 'Loading...',
// What to do if the request fails.
(error: number) => `Error: ${error}`,
// What to do if the request succeeds.
(status: Status) => `Got tweet from ${status.screen_name}`,
);
}
private render(): string {
// Render the current state in your UI.
// `this.view` returns a method which is executed with the current state as a parameter.
const text: string = this.view(this.state);
// Maybe put it in a template.
}
}Using included type guards.
import { RemoteData } from '@abraham/remotedata';
import { Status } from 'twitter-d';
import { getState } from './state';
// Define what the RemoteData Failure and Success types will be.
type State = RemoteData<number, Status>;
const state: State = getState();
if (isSuccess(state)) {
// state is known to be of type Success<Status>
console.log(state.data.full_text);
}