ion-select
Selects are form controls to select an option, or options, from a set of options. When a user taps the select, a dialog appears with all of the options in a large, easy to select list.
A select should be used with child <ion-select-option>
elements. If the child option is not given a value
attribute then its text will be used as the value.
If value
is set on the <ion-select>
, the selected option will be chosen based on that value.
Labels
Labels should be used to describe the select. They can be used visually, and they will also be read out by screen readers when the user is focused on the select. This makes it easy for the user to understand the intent of the select. Select has several ways to assign a label:
Select has several options for supplying a label for the component:
label
property: used for plaintext labelslabel
slot: used for custom HTML labelsaria-label
: used to provide a label for screen readers but adds no visible label
Label Placement
Labels will take up the width of their content by default. Developers can use the labelPlacement
property to control how the label is placed relative to the control. While the label
property is used here, labelPlacement
can also be used with the label
slot.
Label Slot
While plaintext labels should be passed in via the label
property, if custom HTML is needed, it can be passed through the label
slot instead.
No Visible Label
If no visible label is needed, developers should still supply an aria-label
so the select is accessible to screen readers.
Single Selection
By default, the select allows the user to select only one option. The alert interface presents users with a radio button styled list of options. The select component's value receives the value of the selected option's value.
Keyboard interactions for single selection are described in the Keyboard Interactions section below.
Multiple Selection
By adding the multiple
attribute to select, users are able to select multiple options. When multiple options can be selected, the alert or popover overlay presents users with a checkbox styled list of options. The select component's value receives an array of all of the selected option values.
The action-sheet
interface is not supported with multiple selection.
Keyboard interactions for multiple selection are described in the Keyboard Interactions section below.
Interfaces
By default, select uses ion-alert to open up the overlay of options in an alert. The interface can be changed to use ion-action-sheet or ion-popover by passing action-sheet
or popover
, respectively, to the interface
property. Read on to the other sections for the limitations of the different interfaces.
Alert
Action Sheet
Popover
Responding to Interaction
The main ways of handling user interaction with the select are the ionChange
, ionDismiss
, and ionCancel
events. See Events for more details on these and other events that select fires.
Console
Console messages will appear here when logged from the example above.
Object Value References
When using objects for select values, it is possible for the identities of these objects to change if they are coming from a server or database, while the selected value's identity remains the same. For example, this can occur when an existing record with the desired object value is loaded into the select, but the newly retrieved select options now have different identities. This will result in the select appearing to have no value at all, even though the original selection in still intact.
By default, the select uses object equality (===
) to determine if an option is selected. This can be overridden by providing a property name or a function to the compareWith
property.
Using compareWith
Console
Console messages will appear here when logged from the example above.
Object Values and Multiple Selection
Console
Console messages will appear here when logged from the example above.
Justification
Developers can use the justify
property to control how the label and control are packed on a line.
Filled Selects
Material Design offers filled styles for a select. The fill
property on the select can be set to either "solid"
or "outline"
.
Since the fill
styles visually defines the select container, selects that use fill
should not be used in ion-item
.
Select Buttons
The alert supports two buttons: Cancel
and OK
. Each button's text can be customized using the cancelText
and okText
properties.
The action-sheet
and popover
interfaces do not have an OK
button, clicking on any of the options will automatically close the overlay and select that value. The popover
interface does not have a Cancel
button, clicking on the backdrop will close the overlay.
Interface Options
Since select uses the alert, action sheet and popover interfaces, options can be passed to these components through the interfaceOptions
property. This can be used to pass a custom header, subheader, css class, and more.
See the ion-alert docs, ion-action-sheet docs, and ion-popover docs for the properties that each interface accepts.
Note: interfaceOptions
will not override inputs
or buttons
with the alert
interface.
Start and End Slots
The start
and end
slots can be used to place icons, buttons, or prefix/suffix text on either side of the select. If the slot content is clicked, the select will not open.
In most cases, Icon components placed in these slots should have aria-hidden="true"
. See the Icon accessibility docs for more information.
If slot content is meant to be interacted with, it should be wrapped in an interactive element such as a Button. This ensures that the content can be tabbed to.
Customization
There are two units that make up the Select component and each need to be styled separately. The ion-select
element is represented on the view by the selected value(s), or placeholder if there is none, and dropdown icon. The interface, which is defined in the Interfaces section above, is the dialog that opens when clicking on the ion-select
. The interface contains all of the options defined by adding ion-select-option
elements. The following sections will go over the differences between styling these.
Styling Select Element
As mentioned, the ion-select
element consists only of the value(s), or placeholder, and icon that is displayed on the view. To customize this, style using a combination of CSS and any of the CSS custom properties.
Alternatively, depending on the browser support needed, CSS shadow parts can be used to style the select. Notice that by using ::part
, any CSS property on the element can be targeted.
Styling Select Interface
Customizing the interface dialog should be done by following the Customization section in that interface's documentation:
However, the Select Option does set a class for easier styling and allows for the ability to pass a class to the overlay option, see the Select Options documentation for usage examples of customizing options.
Custom Toggle Icons
The icon that displays next to the select text can be set to any Ionicon using the toggleIcon
and/or expandedIcon
properties.
Icon Flip Behavior
By default, when the select is open, the toggle icon will automatically rotate on md
mode and remain static on ios
mode. This behavior can be customized using CSS.
The below example also uses a custom toggleIcon
to better demonstrate the flip behavior on ios
, since the default icon is vertically symmetrical.
Typeahead Component
Typeahead or autocomplete functionality can be built using existing Ionic components. We recommend using an ion-modal
to make the best use of the available screen space.
Interfaces
SelectChangeEventDetail
interface SelectChangeEventDetail<T = any> {
value: T;
}
SelectCustomEvent
While not required, this interface can be used in place of the CustomEvent
interface for stronger typing with Ionic events emitted from this component.
interface SelectCustomEvent<T = any> extends CustomEvent {
detail: SelectChangeEventDetail<T>;
target: HTMLIonSelectElement;
}
Migrating from Legacy Select Syntax
A simpler select syntax was introduced in Ionic 7.0. This new syntax reduces the boilerplate required to setup an select, resolves accessibility issues, and improves the developer experience.
Developers can perform this migration one select at a time. While developers can continue using the legacy syntax, we recommend migrating as soon as possible.
Using the Modern Syntax
Using the modern syntax involves two steps:
- Remove
ion-label
and use thelabel
property onion-select
instead. The placement of the label can be configured using thelabelPlacement
property onion-select
. - Move any usage of
fill
andshape
fromion-item
on toion-select
.
- JavaScript
- Angular
- React
- Vue
<!-- Label and Label Position -->
<!-- Before -->
<ion-item>
<ion-label position="floating">Favorite Fruit:</ion-label>
<ion-select>...</ion-select>
</ion-item>
<!-- After -->
<ion-item>
<ion-select label="Favorite Fruit:" label-placement="floating">...</ion-select>
</ion-item>
<!-- Fill -->
<!-- Before -->
<ion-item fill="outline" shape="round">
<ion-label position="floating">Favorite Fruit:</ion-label>
<ion-select>...</ion-select>
</ion-item>
<!-- After -->
<!-- Inputs using `fill` should not be placed in ion-item -->
<ion-select fill="outline" shape="round" label="Favorite Fruit:" label-placement="floating">...</ion-select>