Function map

Reactivily apply a map function to each element in an array, persisting map-results for each object, based on identity.

This is useful when you have a large collection of items that need to be transformed into a different shape (adding/removing/modifying data/properties) and you want the transform to be efficient when iterating over that data.

A common use case where this map resource provides benefits over is

class MyClass {\
  @cached
  get wrappedRecords() {
    return this.records.map(record => new SomeWrapper(record));
  }
}

Even though the above is @cached, if any tracked data accessed during the evaluation of wrappedRecords changes, the entire array.map will re-run, often doing duplicate work for every unchanged item in the array.

Returns

an object that behaves like an array. This shouldn't be modified directly. Instead, you can freely modify the data returned by the data function, which should be tracked in order to benefit from this abstraction.

Example

 import { map } from 'ember-resources/util/map';

 class MyClass {
   wrappedRecords = map(this, {
     data: () => this.records,
     map: (record) => new SomeWrapper(record),
   }),
 }