How do I accept a key/value pair as an argument to a class method? | TypeScript Community | Page 1

dim shore Jan 21, 2023, 2:30 PM

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This code is throwing an error for some reason:

magicWand([key: string]: Function) {

    }

lost juniper Jan 21, 2023, 2:35 PM

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uh yeah because that's not valid

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what are you trying to do?

dim shore Jan 21, 2023, 2:35 PM

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Why's that?

lost juniper Jan 21, 2023, 2:35 PM

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...i don't even know how to explain that. why do you think it's valid

dim shore Jan 21, 2023, 2:36 PM

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I'll admit I'm basically trying to replicate some code in the form of a class: first answer of this: https://stackoverflow.com/questions/62446219/typescript-javascript-call-function-by-string-name

Stack Overflow

Typescript/Javascript: Call function by string name

I have a *.ts file with lots of exported functions like:

export function newItemFoo() {
return {foo: 0, bar: '', baz: true};
}

export function newItemBar() {
return {foo: 0, bar: ''};
}

...

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I'm new to Typescript, in my head I was passing a key that was of type value and a pointer to a function.

lost juniper Jan 21, 2023, 2:36 PM

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separate parameters are separated by ,

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[K: string]: Function is wrapped inside an object there, that's what makes that valid, it's an index signature

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what kind of input are you expecting with this

dim shore Jan 21, 2023, 2:38 PM

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So I tried making it an object and it still didn't play nice.

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I'm trying to replicate the symbol table from the post above.

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The first answer.

lost juniper Jan 21, 2023, 2:38 PM

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dim shore So I tried making it an object and it still didn't play nice.

you still need an actual parameter

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const magicWand: { [K: string]: Function }
//    ^ name     ^ type
//                 ^ index signature, part of the type

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do you know js?

dim shore Jan 21, 2023, 2:39 PM

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Yeah.

lost juniper Jan 21, 2023, 2:40 PM

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try writing it out in js first

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then add types

dim shore Jan 21, 2023, 2:40 PM

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so a class method?

lost juniper Jan 21, 2023, 2:40 PM

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yeah, start with minimal types

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write it out as you would in js

dim shore Jan 21, 2023, 2:41 PM

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magicWand(pair) { // body }

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pair being an object parameter I guess.

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Is it perhaps an interface that I need to define?

lost juniper Jan 21, 2023, 2:42 PM

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right, so now add type annotations to that method

dim shore Jan 21, 2023, 2:43 PM

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magicWand(pair: object) { // body }

lost juniper Jan 21, 2023, 2:43 PM

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no, that's not correct

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you want pair to be a specifc shape here, so you have to specify that

dim shore Jan 21, 2023, 2:44 PM

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magicWand(pair: {key: string, func: Function}) { // body }

terse edge Jan 21, 2023, 2:44 PM

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where did pair go :(

dim shore Jan 21, 2023, 2:44 PM

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I guess I'm unsure how to annotate sub-properties of an argument.

terse edge Jan 21, 2023, 2:45 PM

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!hb object types

modern apexBOT Jan 21, 2023, 2:45 PM

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Handbook

Object Types

dim shore Jan 21, 2023, 2:45 PM

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Ah cool.

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oh my god

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okay i know what i did wrong

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thanks for the help

#How do I accept a key/value pair as an argument to a class method?