@scottburch/rxjs-msg-bus

Rxjs-msg-bus

A central message bus implimentation for rxjs.

The central msg bus is implimented as a singleton where you can add listeners and fire events.

Defining messages

Messages are defined using a Msg type. The first argument in the type is the string by which this event will be known. The second is the data type for the data sent with the event.

type MyCustomEvent = Msg<'my-custom-event', {name: string}>

Listening for and firing events

Listeners take a message type and pass back a rxjs observable like this.

type NameEnteredEvent = Msg<'name-entered-event', string>


eventListener<NameEnteredEvent>('name-entered-event').subscribe(name => console.log(name)); // Johnny Five
fireEvent<NameEnteredEvent('name-entered-event', 'Johnny Five');

Events are async, they will be fired in the future. There are several other listener functions to fit other scenarios that are described below

Installing

yarn add @scottburch/rxjs-msg-bus

npm install @scottburch/rxjs-msg-bus

Logging events

You can log events for easier troubleshooting by listening to the central bus and console logging the messages.

getCentralMsgBus().subscribe(console.log);

API

Msg<[msg-type-string], [msg-data-type]>

Defines a message type

type UserLoggedInEvent = Msg<'user-logged-in', {username: string, rememberMe: boolean}>

sendEvent<[MsgType]>([msg-type-string], [data]);

Sends an event of MsgTypecontaining data

type UserLoggedInEvent = Msg<'user-logged-in', {username: string, rememberMe: boolean}>;

eventListener<UserLoggedInEvent('user-logged-in').pipe(
	tap(data => verifyUser(data))
).subscribe();

fireEvent<UserLoggedInEvent('user-logged-in', {username: 'scott', rememberMe: true});

eventListener<[MsgType]>([msg-type-string]);

Listens for an event

type UserLoggedInEvent = Msg<'user-logged-in', {username: string, rememberMe: boolean}>;

eventListener<UserLoggedInEvent('user-logged-in').pipe(
	tap(data => verifyUser(data))
).subscribe();

fireEvent<UserLoggedInEvent('user-logged-in', {username: 'scott', rememberMe: true});

eventListenerOnce<[MsgType]>([msg-type-string]);

Same as eventListenerexcept it only fires once and then unsubscribes.

eventListenerMatchOnce<[MsgType]>([msg-type-string], data => true/false)

Same as eventListenerOnce except it takes a matcher function. If the function returns true, the rest of the code is run and the listener is unsubscribed.

type UserReadEvent = Msg<'user-read', UserId>;

eventListenerMatchOnce<UserReadEvent>('user-read', userId => userId === '12345').subscribe(
  // only user 12345 will show up here
)

fireEvent<UserReadEvent>('user-read', '22222')  // will not trigger listener code
fireEvent<UserReadEvent>('user-read', '12345')  // will trigger listener code

sendEventPartial<[MsgType]>([msg-type-string]);

Same as sendEventexcept it is a curried function where the result is partially applied

type UserLoggedInEvent = Msg<'user-logged-in', {username: string}>
type ReadUser = Msg<'read-user', User>

eventListener<UserLoggedInEvent>('user-logged-in').subscribe(sendEventPartial<ReadUser>('read-user'));