CODEWITHSUNDEEP
typescriptmapped-types
NSjonas
NSjonas

Reputation: 12032

Mapping Enum to Type

I'm trying to use mapped type on an enum: 

export enum CurrencyType {
  USD = "USD",
  AUD = "AUD",
  GBP = "GBP",
  CAD = "CAD"
}

to achieve this type:

type Rates = {
  AUD: number;
  CAD: number;
  GBP: number;
  USD: number;
}

I thought I could do something like this:

type Rates = {
  [P in keyof CurrencyType]: number;
};

but that results in this instead:

type Rates = {
    toString: number;
    charAt: number;
    charCodeAt: number;
    concat: number;
    indexOf: number;
    lastIndexOf: number;
    localeCompare: number;
    match: number;
    replace: number;
    //...
}

I tried using union literals instead of enum, 

export type CurrencyType = "USD" | "AUD" | "GBP" | "CAD";`

but it gives the same result.

The only thing I can get to work, is by doing this:

type Rates = {
  [P in typeof CurrencyType.AUD | CurrencyType.USD | CurrencyType.GBP | CurrencyType.CAD]: number;
};

but obviously that defeats the whole purpose!

Is there anyway to do this?

Upvotes: 4

Views: 2451

Answers (1)

NSjonas
NSjonas

Reputation: 12032

wow it was right in front of me. As always, I was over complicating it and not reading the documentation thoroughly.

type Rate = {
  [P in CurrencyType]: number;
};

I'll leave this up in case it helps someone else

Upvotes: 15

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