https://github.com/connorjameslow/subject-matter

https://github.com/connorjameslow/subject-matter

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• Host: GitHub
• URL: https://github.com/connorjameslow/subject-matter
• Owner: ConnorJamesLow
• Created: 2022-07-10T05:45:45.000Z (over 2 years ago)
• Default Branch: main
• Last Pushed: 2022-07-10T05:49:54.000Z (over 2 years ago)
• Last Synced: 2023-03-07T19:21:33.194Z (almost 2 years ago)
• Language: TypeScript
• Size: 33.2 KB
• Stars: 0
• Watchers: 1
• Forks: 0
• Open Issues: 0
• Metadata Files:
  • Readme: README.md

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README

        
A simple `Subject` for the observer pattern.

## Documentation

### `Subject` Class

Holds a bit of state and a list of subscribers.

#### Constructor

Requires one parameter representing the initial state.

```ts

const subject = new Subject(0);

```

#### Protected Fields

If you'd like to extend `Subject`, note the following protected (using typescript) fields are available

 - `__data: T`: the current state.

 - `__observers: Record>`: a record of all currently subscribed observers.

#### Methods

 - `subscribe(observer: Observer): Unsubscriber`: adds an observer to notify when a change is pushed. Also immediately calls the observer with the current state.

 - `push(next: T): void`: push a change to observers. Other overloads:

   - `push(resolve: Updater): void`

#### Type Declaration

Where `T` is the type of data passed to the `Subject` instance.

```ts

type Observer = (d?: T) => any;

type Unsubscriber = () => boolean;

type Updater = (v?: T) => T;

```

### Example

```ts

// Create a new Subject (T = string)

const subject = new Subject('world');

// Add an observer:

const unsubscribe = subject.subscribe(v => console.log(`hello  ${v}`)); // logs "hello world"

// Push an update

subject.push('there'); // logs "hello there"

// Unsubscribe observer when done listening for changes.

unsubscribe(); // returns true

// subject.push('...') won't call the above observer anymore.

```