functions-delegate

This package, inspired by C# multicast delegation system, allow dynamic mapping of several functions/methods inside a single 'delegate' object which can later be invoked or passed as a function.

Getting started

npm i functions-delegate

import { ActionDelegate } from "functions-delegate";
import { FunctionDelegate } from "functions-delegate";

ActionDelegate vs FunctionDelegate

Both ActionDelegate and FunctionDelegate share the same interface. However, the main difference between the two classes is the return type of the invocation method.

ActionDelegate ignores the return value of the registered functions. In other words actionDelegate.invoke(..) is void. FunctionDelegate, however, will return an array containing every return value of the called functions.

See bellow for further details.

Usage

ActionDelegate

import { ActionDelegate } from "functions-delegate";

let delegate = new ActionDelegate();

let f1 = (a:string) => {
    console.log(`Hello ${a} from 1`);
}

function f2(a:string) {
    console.log(`Hello ${a} from 2`);
}

let f3 = function (a:string) {
    console.log(`Hello ${a} from 3`);
}

let action = delegate.add(f1).add(f3).add(f2).asFunction();
action('Bob');

console.log('Removing f1');
delegate.remove(f1);
delegate.invoke('Roger') //or action('Roger');

Would prints :

Hello Bob from 1
Hello Bob from 3
Hello Bob from 2
Removing f1
Hello Roger from 3
Hello Roger from 2

FunctionDelegate

import { FunctionDelegate } from "functions-delegate";

let delegate = new FunctionDelegate();

let f1 = (a:string) => {
    return `Hello ${a} from 1`;
}

let f2 = (a:string) => {
    return `Hello ${a} from 2`;
}

let action = delegate.add(f2).add(f1).asFunction();
let results = action('Bob'); //or delegate.invoke('Bob')

console.log(results)

Would prints :

['Hello Bob from 2', 'Hello Bob from 1']

Interface details

add(f:DelegateFunction): Delegate

Adds (register) a given function / method to this delegate

remove(f:DelegateFunction): Delegate

Remove (unregister) a given function / method of this delegate

invoke(...args: any[]): void | any[]

Invoke this delegate with the given arguments

Calls all registered functions with the given arguments

This method is void for ActionDelegate, and returns an array of result (any[]) for FunctionDelegate

asFunction(): DelegateFunction

Returns a function that can be called later to invoke the delegate

Example :

let action = new ActionDelegate().add(f1).add(f3).add(f2).asFunction();
action(`Bob`);

// Has the same result than
new ActionDelegate().add(f1).add(f3).add(f2).invoke('Bob');