There's a couple of questions related to this but none I could find that match my requirements.
I wish to create a factory that, based on the type, requires a factory for each key of that object that contains the value and the entire object. For example:
type Row = {
foo: string
bar: number
baz: unknown
}
const factory: MyMagicType<Row> = [{
field: 'foo',
// Infers value as string
factory: (value, obj) => ..
}, {
field: 'bar',
// Infers value as number
factory: (value, obj) => ..
}]
^also throws that 'baz' hasn't been populated
I have tried using generics for this but got stuck.
type MyMagicType<TObj extends Record<string, unknown>, TField extends keyof TObj> {
field: TField,
factory: (val: TObj[TField], source: TObj) => any
}[]
But this doesn't work due to the field needing to be inferred rather than passed into the generic.
How can I omit the TField but still let it infer from field?
CodePudding user response：
Not sure how you want to type the second parameter and the return value of your factory functions, but here is a possible implementation of MyMagicType that types the first parameter correctly:
type Row = {
foo: string
bar: number
baz: unknown
};
type MyMagicType<T extends object> = Array<{
[K in keyof T]: {
field: K,
factory: (value: T[K], obj: any) => any,
}
}[keyof T]>;
const factory: MyMagicType<Row> = [{
field: 'foo',
// Infers value as string
factory: (value, obj) => undefined
}, {
field: 'bar',
// Infers value as number
factory: (value, obj) => undefined
}];