Typescript use keyof when passing an array as type

Question

I have the following interfaces:

interface ColDef<Entity, Field extends keyof Entity> {
    field: Field;
    valueGetter(value: Entity[Field], entity: Entity): any
}


interface Options<Entity> {
    colDefs: ColDef<Entity, ??>[]
}

const options: Options<{ name: string }> = {
    colDefs: [{
        field: 'name',
        valueGetter(value) {
        // how do I make value typed as string??
        }
    }]
}

I want to infer the entity field type in the valueGetter function. The issue is that I ColDef is required the key as the second generic, but I'm passing an array. How can I solve this?

Dimava · Accepted Answer · 2022-12-11 13:18:46Z

1

interface ColDef<Entity, Field extends keyof Entity> {
  field: Field;
  valueGetter(value: Entity[Field], entity: Entity): any
}

type A = {
  name: string;
  age: number;
}


interface Options<Entity> {
  colDefs: { [K in keyof Entity]: ColDef<Entity, K> }[keyof Entity][]
}

type What = { [K in keyof A]: ColDef<A, K> }
//   ^?
// type What = {
//     name: ColDef<A, "name">;
//     age: ColDef<A, "age">;
// }

type What1 = { [K in keyof A]: ColDef<A, K> }[keyof A]
//   ^?
// type What1 = ColDef<A, "name"> | ColDef<A, "age">


const options: Options<A> = {
  colDefs: [{
    field: 'name',
    valueGetter(value) {
      //        ^? (parameter) value: string
      // how do I make value typed as string??
    }
  }]
}

answered Dec 11, 2022 at 13:18

Dimava

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