Transfer List

• Introduction
• Getting started
  • Base input
  • Labels
  • Defining options
  • Values
  • Searchable
  • Max
  • Transfer on select
• Asynchrony
  • Asynchronous options
  • Option loader
• Slots
  • Source and target options
• Examples
  • Ranked order
• Props & Attributes
• Sections
  • Wrapper of transfer list
  • Source
  • Transfer controls
  • Target
• Accessibility
  • Keyboard Interactions

Introduction

The transfer list input is ideal for situations where the end-user needs to select and sort multiple values from a list of options. In this example, we are allowing the end-user to select from a group of guests and move them to a VIP list:

Getting started

In this section, we will be covering the basics of how to replicate the 'Guests vs VIPs' example from above.

Base input

Below is an example of the transfer list input with the minimum required props. As you can see, there are two list boxes: the source list box and the target list box. The source list box will contain the list of options, and the target list box will contain the selected options:

Labels

Let's add some label props to make clear to the end-user how to use the transfer list input. We'll add a label prop to explain the directive to the user, and source-label and target-label props to indicate which list box is the source and which is the target:

Source and target empty messages

In this state, with no options passed and no values selected, we can display a custom message to the user by setting the source-empty-message and target-empty-message props:

Defining options

The options prop can accept three different formats of values:

• An array of objects with value and label keys
• An array of strings 'A', 'B', 'C'
• An object literal with key-value pairs { a: 'A', b: 'B', c: 'C' }
• A function that returns any of the above

Let's go ahead and populate the transfer list's options with a list of guest names:

Values

The value of the transfer list input is an array. Selected option values from the source list will be appended to the array. To show the value changing in the example below, let's wrap the transfer list input in a FormKit form, set the name of the transfer list input to vips, and show the value of the form itself in a <pre> tag (if you are unfamiliar with FormKit forms, you can read more here):

Initial values

The transfer list input can be pre-populated with values by setting the value prop on the transferlist itself or a wrapping form or group. Remember that the values you pass to the value prop need to match the keys of the values in your option list:

Searchable

The transfer list input can be made searchable by setting the searchable prop. In this example we'll set the searchable prop and also set a placeholder prop for the search input:

Filtering

The transfer list input will filter options with its own internal search function. You can replace this search function by providing the filter prop a function of your own. Your function will receive two arguments, the option being iterated over and the current search value:

Clear on select

By default, the transfer list input will clear the search input on select. You can change this behavior by setting the clear-on-select prop to false:

Max

The transfer list input can be limited to a maximum number of selected values by setting the max prop. For just this example, let's set the max prop to 2 to limit the number of VIPs that can be selected:

Transfer on select

By default, the transfer list input will add or remove options on click. You can change this behavior by setting the transfer-on-select prop to false. Now, the transfer list will behave more like a traditional transfer list:

Asynchrony

Asynchronous options

Here we have a transfer list input that loads its options from an asynchronous function. The function is called when the component is mounted and the options are subsequently loaded into the source list box:

Pagination

Now let's say that our API request does not fetch all the options we need, but instead returns a paginated response. The transfer list input can handle pagination with minor configuration to the asynchronous function.

When assigning the options prop to an asynchronous function, the function will be called with the FormKit context object as its first argument. This context object contains a page property (the current page we are attempting to load) that is tracked by the transfer list input, and hasNextPage, which is a callback function we can use to tell the transfer list that there are more options to load:

Search

The transfer list input can also load options asynchronously when the user searches. In this example, we'll add back the searchable prop, and change getGuests() to searchGuests(). When the user searches, searchGuests() will now be called with the same context object as before, but this time, we will destructure just the search property. Additionally, we'll modify getGuests() to only return guests when a search value is provided:

Option loader

Rehydrating values

The transfer list input also provides an optionLoader prop that allows you to rehydrate values that are not in the options list. In this example, we'll provide the transfer list an initial value (a guest ID), and assign the optionLoader to a function that will make a request to the API to fetch the individual guest data:

Notice in the example above that the optionLoader function getGuest is passed two arguments: the value of the selected option (in this case, the movie ID) and the cachedOption. The cachedOption is used for preventing unnecessary lookups; if the cachedOption is not null it means the selected option has already been loaded, and you can return the cachedOption directly.

Fetching additional data

You can also use use the optionLoader to fetch additional data on selected values that is not already in the options list. In this example, after selecting an option, we are going to perform a look-up to load the selected guest's age:

Slots

Just like any other FormKit input, the transfer list input allows you to utilize slots to customize its markup.

Source and target options

Now that we are loading additional data on selected values (the age and email address of the selected guest), let's customize the look of the selected values by using the target-option slots:

Examples

Ranked order

The transfer list input can be used to create a ranked list, let's do that with the greatest NBA players:

Props & Attributes

Sections

You can target a specific section of an input using that section's "key", allowing you to modify that section's classes, HTML (via :sections-schema), or content (via slots). Read more about sections here.

Wrapper of transfer list

Source

Transfer controls

Target

Accessibility

All FormKit inputs are designed with the following accessibility considerations in mind. Help us continually improve accessibility for all by filing accessibility issues here:

Keyboard Interactions