Query Parameters

Query parameters are optional key-value pairs that appear to the right of the ? in a URL. For example, the following URL has two query params, sort and page, with respective values ASC and 2:

http://example.com/articles?sort=ASC&page=2

Query params allow for additional application state to be serialized into the URL that can't otherwise fit into the path of the URL (i.e. everything to the left of the ?). Common use cases for query params include representing the current page number in a paginated collection, filter criteria, or sorting criteria.

Specifying Query Parameters

Query params are declared on route-driven controllers. For example, to configure query params that are active within the articles route, they must be declared on controller:articles.

To add a category query parameter that will filter out all the articles that haven't been categorized as popular we'd specify 'category' as one of controller:article's queryParams:

import Ember from 'ember';

export default Ember.Controller.extend({
  queryParams: ['category'],
  category: null
});

This sets up a binding between the category query param in the URL, and the category property on controller:articles. In other words, once the articles route has been entered, any changes to the category query param in the URL will update the category property on controller:articles, and vice versa. Note that you can't bind queryParams to computed properties, they have to be values.

Now we need to define a computed property of our category-filtered array that the articles template will render:

import Ember from 'ember';

export default Ember.Controller.extend({
  queryParams: ['category'],
  category: null,

  filteredArticles: Ember.computed('category', 'model', function() {
    let category = this.get('category');
    let articles = this.get('model');

    if (category) {
      return articles.filterBy('category', category);
    } else {
      return articles;
    }
  })
});

With this code, we have established the following behaviors:

1. If the user navigates to /articles, category will be null, so the articles won't be filtered.
2. If the user navigates to /articles?category=recent, category will be set to "recent", so articles will be filtered.
3. Once inside the articles route, any changes to the category property on controller:articles will cause the URL to update the query param. By default, a query param property change won't cause a full router transition (i.e. it won't call model hooks and setupController, etc.); it will only update the URL.

link-to Helper

The link-to helper supports specifying query params using the query-params subexpression helper.

// Explicitly set target query params
{{#link-to "posts" (query-params direction="asc")}}Sort{{/link-to}}

// Binding is also supported
{{#link-to "posts" (query-params direction=otherDirection)}}Sort{{/link-to}}

In the above examples, direction is presumably a query param property on the posts controller, but it could also refer to a direction property on any of the controllers associated with the posts route hierarchy, matching the leaf-most controller with the supplied property name.

The link-to helper takes into account query parameters when determining its "active" state, and will set the class appropriately. The active state is determined by calculating whether the query params end up the same after clicking a link. You don't have to supply all of the current, active query params for this to be true.

transitionTo

Route#transitionTo and Controller#transitionToRoute accept a final argument, which is an object with the key queryParams.

this.transitionTo('post', object, { queryParams: { showDetails: true }});
this.transitionTo('posts', { queryParams: { sort: 'title' }});

// if you want to transition the query parameters without changing the route
this.transitionTo({ queryParams: { direction: 'asc' }});

You can also add query params to URL transitions:

this.transitionTo('/posts/1?sort=date&showDetails=true');

Opting into a full transition

Arguments provided to transitionTo or link-to only correspond to a change in query param values, and not a change in the route hierarchy, it is not considered a full transition, which means that hooks like model and setupController won't fire by default, but rather only controller properties will be updated with new query param values, as will the URL.

But some query param changes necessitate loading data from the server, in which case it is desirable to opt into a full-on transition. To opt into a full transition when a controller query param property changes, you can use the optional queryParams configuration hash on the Route associated with that controller, and set that query param's refreshModel config property to true:

import Ember from 'ember';

export default Ember.Route.extend({
  queryParams: {
    category: {
      refreshModel: true
    }
  },
  model(params) {
    // This gets called upon entering 'articles' route
    // for the first time, and we opt into refiring it upon
    // query param changes by setting `refreshModel:true` above.

    // params has format of { category: "someValueOrJustNull" },
    // which we can forward to the server.
    return this.get('store').query('article', params);
  }
});

import Ember from 'ember';

export default Ember.Controller.extend({
  queryParams: ['category'],
  category: null
});

Update URL with replaceState instead

By default, Ember will use pushState to update the URL in the address bar in response to a controller query param property change, but if you would like to use replaceState instead (which prevents an additional item from being added to your browser's history), you can specify this on the Route's queryParams config hash, e.g. (continued from the example above):

import Ember from 'ember';

export default Ember.Route.extend({
  queryParams: {
    category: {
      replace: true
    }
  }
});

Note that the name of this config property and its default value of false is similar to the link-to helper's, which also lets you opt into a replaceState transition via replace=true.

Map a controller's property to a different query param key

By default, specifying foo as a controller query param property will bind to a query param whose key is foo, e.g. ?foo=123. You can also map a controller property to a different query param key using the following configuration syntax:

import Ember from 'ember';

export default Ember.Controller.extend({
  queryParams: {
    category: 'articles_category'
  },
  category: null
});

This will cause changes to the controller:articles's category property to update the articles_category query param, and vice versa.

Note that query params that require additional customization can be provided along with strings in the queryParams array.

import Ember from 'ember';

export default Ember.Controller.extend({
  queryParams: ['page', 'filter', {
    category: 'articles_category'
  }],
  category: null,
  page: 1,
  filter: 'recent'
});

Default values and deserialization

In the following example, the controller query param property page is considered to have a default value of 1.

import Ember from 'ember';

export default Ember.Controller.extend({
  queryParams: 'page',
  page: 1
});

This affects query param behavior in two ways:

1. Query param values are cast to the same datatype as the default value, e.g. a URL change from /?page=3 to /?page=2 will set controller:articles's page property to the number 2, rather than the string "2". The same also applies to boolean default values.
2. When a controller's query param property is currently set to its default value, this value won't be serialized into the URL. So in the above example, if page is 1, the URL might look like /articles, but once someone sets the controller's page value to 2, the URL will become /articles?page=2.

Sticky Query Param Values

By default, query param values in Ember are "sticky", in that if you make changes to a query param and then leave and re-enter the route, the new value of that query param will be preserved (rather than reset to its default). This is a particularly handy default for preserving sort/filter parameters as you navigate back and forth between routes.

Furthermore, these sticky query param values are remembered/restored according to the model loaded into the route. So, given a team route with dynamic segment /:team_name and controller query param "filter", if you navigate to /badgers and filter by "rookies", then navigate to /bears and filter by "best", and then navigate to /potatoes and filter by "worst", then given the following nav bar links,

{{#link-to "team" "badgers"}}Badgers{{/link-to}}
{{#link-to "team" "bears"}}Bears{{/link-to}}
{{#link-to "team" "potatoes"}}Potatoes{{/link-to}}

the generated links would be

<a href="/badgers?filter=rookies">Badgers</a>
<a href="/bears?filter=best">Bears</a>
<a href="/potatoes?filter=worst">Potatoes</a>

This illustrates that once you change a query param, it is stored and tied to the model loaded into the route.

If you wish to reset a query param, you have two options:

1. explicitly pass in the default value for that query param into link-to or transitionTo.
2. use the Route.resetController hook to set query param values back to their defaults before exiting the route or changing the route's model.

In the following example, the controller's page query param is reset to 1, while still scoped to the pre-transition ArticlesRoute model. The result of this is that all links pointing back into the exited route will use the newly reset value 1 as the value for the page query param.

import Ember from 'ember';

export default Ember.Route.extend({
  resetController(controller, isExiting, transition) {
    if (isExiting) {
      // isExiting would be false if only the route's model was changing
      controller.set('page', 1);
    }
  }
});

In some cases, you might not want the sticky query param value to be scoped to the route's model but would rather reuse a query param's value even as a route's model changes. This can be accomplished by setting the scope option to "controller" within the controller's queryParams config hash:

import Ember from 'ember';

export default Ember.Controller.extend({
  queryParams: [{
    showMagnifyingGlass: {
      scope: 'controller'
    }
  }]
});

The following demonstrates how you can override both the scope and the query param URL key of a single controller query param property:

import Ember from 'ember';

export default Ember.Controller.extend({
  queryParams: ['page', 'filter',
    {
      showMagnifyingGlass: {
        scope: 'controller',
        as: 'glass'
      }
    }
  ]
});