Function

readOnly (dependentKey) ComputedProperty public

Module:	@ember/object

Defined in packages/@ember/object/lib/computed/computed_macros.js:1076

Available since v1.5.0

import { readOnly } from '@ember/object/computed';

dependentKey

String

returns

ComputedProperty

computed property which creates a one way computed property to the original value for property.

Where computed.oneWay provides oneWay bindings, computed.readOnly provides a readOnly one way binding. Very often when using computed.oneWay one does not also want changes to propagate back up, as they will replace the value.

This prevents the reverse flow, and also throws an exception when it occurs.

Example:

import { set } from '@ember/object';
import { readOnly } from '@ember/object/computed';

class User {
  constructor(firstName, lastName) {
    set(this, 'firstName', firstName);
    set(this, 'lastName', lastName);
  }

  @readOnly('firstName') nickName;
});

let teddy = new User('Teddy', 'Zeenny');

teddy.nickName; // 'Teddy'

set(teddy, 'nickName', 'TeddyBear'); // throws Exception
// throw new EmberError('Cannot Set: nickName on: <User:ember27288>' );`

teddy.firstName; // 'Teddy'

Classic Class Example:

import EmberObject, { set } from '@ember/object';
import { readOnly } from '@ember/object/computed';

let User = EmberObject.extend({
  firstName: null,
  lastName: null,

  nickName: readOnly('firstName')
});

let teddy = User.create({
  firstName: 'Teddy',
  lastName:  'Zeenny'
});

teddy.nickName; // 'Teddy'

set(teddy, 'nickName', 'TeddyBear'); // throws Exception
// throw new EmberError('Cannot Set: nickName on: <User:ember27288>' );`

teddy.firstName; // 'Teddy'