Function defineMapper

defineMapper<T, V, R>(reader: Func<T, V>, builder: Func<V, R>): Func<T, R>

Defines a mapper that reads the values from an input and invokes a builder to transform data from one schema to another.

Type Parameters

Parameters

reader: Func<T, V>
The mapper that reads values from the input an creates an intermediate format that will be passed to the builder.
builder: Func<V, R>
A mapper that takes the output of reader and constructs the output format.

Returns Func<T, R>

Example

import { Mapper as M } from '@vertexvis/utils';

interface Address {
  address: string;
  city: string;
  state: string;
  zip: string;
}

interface Person {
  name: string;
  addresses: Address[];
}

type AddressJson = Partial<Address>;
type PersonJson = {
  name?: string;
  addresses?: AddressJson[];
}

const mapAddress: M.Func<AddressJson, Address> = M.defineMapper(
  M.read(
    M.requireProp('address'),
    M.requireProp('city'),
    M.requireProp('state'),
    M.requireProp('zip')
  ),
  ([address, city, state, zip]) => ({
    address, city, state, zip
  })
);

const mapPerson: M.Func<PersonJson, Person> = M.defineMapper(
  M.read(
    M.requireProp('name'),
    M.mapProp(
      'addresses',
      M.compose(M.required('addresses'), M.mapArray(mapAddress))
    )
  ),
  ([name, addresses]) => ({ name, addresses })
)

const person = mapPerson({
  name: 'John',
  addresses: [{ address: '123', city: 'Ames', state: 'IA', zip: '50010' }]
})

See

read - a helper function to read and validate input values.