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andremichelle/callIfExists.ts

Last active October 28, 2022 14:13
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Safe call to optional methods in interface (nice for visitor pattern)
Raw
callIfExists.ts
class Bar { type: 'bar' = 'bar' }
interface Foo {
hello?(): string
world?(event: Bar, foo: number): string
george?(): string
}
const bar: Foo = {
hello: () => 'world',
world: (bar: Bar, foo: number) => `bar is ${bar.type} and foo is ${foo}`
}
const callIfExists = <F extends (...args: any[]) => any>
(func: F | undefined, ...args: Parameters<F>): ReturnType<F> | void =>
{ if (func !== undefined) return func.apply(null, args) }
console.log(callIfExists(bar.hello))
console.log(callIfExists(bar.world, new Bar(), 42))
console.log(callIfExists(bar.george))
// These will produce errors
// const r: number = callIfExists(bar.hello)
// callIfExists(bar.hello, 1)
// callIfExists(bar.world)
// callIfExists(bar.world, new Bar(), '42')
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