I have these two interfaces
interface PersonRequirements{
user:string,
password:string,
id:number
}
export interface Requirement<R> {
name: keyof R & string,
save: () => any,/* I want this return type to be same as return type of founded key in R*/
}
and here is my use case elsewhere
const idRequirement:Requirement<PersonRequirements>={
name:"id",
save:function ():number/* I want this return type to be same as id's return type(number) but in a generic type safe way*/{
//
}
}
I want to make save() return type to be same as id's return type but in a generic type safe way how can I do that ?
You can declare another generic parameter that takes the property name in at compile time.
export interface Requirement<R, N extends keyof R & string> {
name: N; // this will force the name property to be the same as being passed in
save(): R[N];
}
Then using it like this
const idRequirement: Requirement<PersonRequirements, "id"> ={
name: "id",
save: () => 0
}