BelongsToReference Class
A BelongsToReference
is a low-level API that allows access
and manipulation of a belongsTo relationship.
It is especially useful when you're dealing with async
relationships
from @ember-data/model
as it allows synchronous access to
the relationship data if loaded, as well as APIs for loading, reloading
the data or accessing available information without triggering a load.
It may also be useful when using sync
relationships with @ember-data/model
that need to be loaded/reloaded with more precise timing than marking the
relationship as async
and relying on autofetch would have allowed.
However,keep in mind that marking a relationship as async: false
will introduce
bugs into your application if the data is not always guaranteed to be available
by the time the relationship is accessed. Ergo, it is recommended when using this
approach to utilize links
for unloaded relationship state instead of identifiers.
Reference APIs are entangled with the relationship's underlying state, thus any getters or cached properties that utilize these will properly invalidate if the relationship state changes.
References are "stable", meaning that multiple calls to retrieve the reference for a given relationship will always return the same HasManyReference.
Item Index
Properties
Methods
id
()
String
public
The id
of the record that this reference refers to. Together, the
type()
and id()
methods form a composite key for the identity
map. This can be used to access the id of an async relationship
without triggering a fetch that would normally happen if you
attempted to use record.relationship.id
.
Example
// models/blog.js
import Model, { belongsTo } from '@ember-data/model';
export default class BlogModel extends Model {
@belongsTo('user', { async: true, inverse: null }) user;
}
let blog = store.push({
data: {
type: 'blog',
id: 1,
relationships: {
user: {
data: { type: 'user', id: 1 }
}
}
}
});
let userRef = blog.belongsTo('user');
// get the identifier of the reference
if (userRef.remoteType() === "id") {
let id = userRef.id();
}
Returns:
The id of the record in this belongsTo relationship.
link
()
String
public
The link Ember Data will use to fetch or reload this belongs-to relationship. By default it uses only the "related" resource linkage.
Example
// models/blog.js
import Model, { belongsTo } from '@ember-data/model';
export default Model.extend({
user: belongsTo('user', { async: true, inverse: null })
});
let blog = store.push({
data: {
type: 'blog',
id: 1,
relationships: {
user: {
links: {
related: '/articles/1/author'
}
}
}
}
});
let userRef = blog.belongsTo('user');
// get the identifier of the reference
if (userRef.remoteType() === "link") {
let link = userRef.link();
}
Returns:
The link Ember Data will use to fetch or reload this belongs-to relationship.
links
()
public
any links that have been received for this relationship
Returns:
load
-
options
Loads a record in a belongs-to relationship if it is not already loaded. If the relationship is already loaded this method does not trigger a new load.
Example
// models/blog.js
import Model, { belongsTo } from '@ember-data/model';
export default class BlogModel extends Model {
@belongsTo('user', { async: true, inverse: null }) user;
}
let blog = store.push({
data: {
type: 'blog',
id: 1,
relationships: {
user: {
data: { type: 'user', id: 1 }
}
}
}
});
let userRef = blog.belongsTo('user');
userRef.value(); // null
userRef.load().then(function(user) {
userRef.value() === user
});
You may also pass in an options object whose properties will be
fed forward. This enables you to pass adapterOptions
into the
request given to the adapter via the reference.
Example
userRef.load({ adapterOptions: { isPrivate: true } }).then(function(user) {
userRef.value() === user;
});
import Adapter from '@ember-data/adapter';
export default class UserAdapter extends Adapter {
findRecord(store, type, id, snapshot) {
// In the adapter you will have access to adapterOptions.
let adapterOptions = snapshot.adapterOptions;
}
});
Parameters:
-
options
Objectthe options to pass in.
Returns:
a promise that resolves with the record in this belongs-to relationship.
meta
()
Object
public
The meta data for the belongs-to relationship.
Example
// models/blog.js
import Model, { belongsTo } from '@ember-data/model';
export default Model.extend({
user: belongsTo('user', { async: true, inverse: null })
});
let blog = store.push({
data: {
type: 'blog',
id: 1,
relationships: {
user: {
links: {
related: {
href: '/articles/1/author'
},
},
meta: {
lastUpdated: 1458014400000
}
}
}
}
});
let userRef = blog.belongsTo('user');
userRef.meta() // { lastUpdated: 1458014400000 }
Returns:
The meta information for the belongs-to relationship.
push
-
doc
-
[skipFetch]
push
can be used to update the data in the relationship and EmberData
will treat the new data as the canonical value of this relationship on
the backend. A value of null
(e.g. { data: null }
) can be passed to
clear the relationship.
Example model
import Model, { belongsTo } from '@ember-data/model';
export default class BlogModel extends Model {
@belongsTo('user', { async: true, inverse: null }) user;
}
Setup some initial state, note we haven't loaded the user yet:
const blog = store.push({
data: {
type: 'blog',
id: '1',
relationships: {
user: {
data: { type: 'user', id: '1' }
}
}
}
});
const userRef = blog.belongsTo('user');
userRef.id(); // '1'
Update the state using push
, note we can do this even without
having loaded the user yet by providing a resource-identifier.
Both full a resource and a resource-identifier are supported.
await userRef.push({
data: {
type: 'user',
id: '2',
}
});
userRef.id(); // '2'
You may also pass in links and meta fore the relationship, and sideload additional resources that might be required.
await userRef.push({
data: {
type: 'user',
id: '2',
},
links: {
related: '/articles/1/author'
},
meta: {
lastUpdated: Date.now()
},
included: [
{
type: 'user-preview',
id: '2',
attributes: {
username: '@runspired'
}
}
]
});
By default, the store will attempt to fetch the record if it is not loaded or its
resource data is not included in the call to push
before resolving the returned
promise with the new state..
Alternatively, pass true
as the second argument to avoid fetching unloaded records
and instead the promise will resolve with void without attempting to fetch. This is
particularly useful if you want to update the state of the relationship without
forcing the load of all of the associated record.
Parameters:
-
doc
Objecta JSONAPI document object describing the new value of this relationship.
-
[skipFetch]
Boolean optionalif
true
, do not attempt to fetch unloaded records
Returns:
reload
-
options
Triggers a reload of the value in this relationship. If the
remoteType is "link"
Ember Data will use the relationship link to
reload the relationship. Otherwise it will reload the record by its
id.
Example
// models/blog.js
import Model, { belongsTo } from '@ember-data/model';
export default class BlogModel extends Model {
@belongsTo('user', { async: true, inverse: null }) user;
}
let blog = store.push({
data: {
type: 'blog',
id: 1,
relationships: {
user: {
data: { type: 'user', id: 1 }
}
}
}
});
let userRef = blog.belongsTo('user');
userRef.reload().then(function(user) {
userRef.value() === user
});
You may also pass in an options object whose properties will be
fed forward. This enables you to pass adapterOptions
into the
request given to the adapter via the reference. A full example
can be found in the load
method.
Example
userRef.reload({ adapterOptions: { isPrivate: true } })
Parameters:
-
options
Objectthe options to pass in.
Returns:
a promise that resolves with the record in this belongs-to relationship after the reload has completed.
remoteType
()
String
public
This returns a string that represents how the reference will be looked up when it is loaded. If the relationship has a link it will use the "link" otherwise it defaults to "id".
Example
import Model, { hasMany } from '@ember-data/model';
export default class PostModel extends Model {
@hasMany('comment', { async: true, inverse: null }) comments;
}
let post = store.push({
data: {
type: 'post',
id: 1,
relationships: {
comments: {
data: [{ type: 'comment', id: 1 }]
}
}
}
});
let commentsRef = post.hasMany('comments');
// get the identifier of the reference
if (commentsRef.remoteType() === "ids") {
let ids = commentsRef.ids();
} else if (commentsRef.remoteType() === "link") {
let link = commentsRef.link();
}
Returns:
The name of the remote type. This should either be link
or id
value
()
Model
public
value()
synchronously returns the current value of the belongs-to
relationship. Unlike record.relationshipName
, calling
value()
on a reference does not trigger a fetch if the async
relationship is not yet loaded. If the relationship is not loaded
it will always return null
.
Example
// models/blog.js
import Model, { belongsTo } from '@ember-data/model';
export default class BlogModel extends Model {
@belongsTo('user', { async: true, inverse: null }) user;
}
let blog = store.push({
data: {
type: 'blog',
id: 1,
relationships: {
user: {
data: { type: 'user', id: 1 }
}
}
}
});
let userRef = blog.belongsTo('user');
userRef.value(); // null
// provide data for reference
userRef.push({
data: {
type: 'user',
id: 1,
attributes: {
username: "@user"
}
}
}).then(function(user) {
userRef.value(); // user
});
Returns:
the record in this relationship
Properties
identifier
StableRecordIdentifier | null
public
The identifier of the record that this reference refers to.
null
if no related record is known.
key
String
public
The field name on the parent record for this has-many relationship.
type
String
public
The type of resource this relationship will contain.