In fastn, the list keyword can be used to create an array or list of values. The list keyword is followed by the data type of the values that the list will contain.

Declaring a `list`

To declare a new list variable, you can use the following syntax:

Declaring a list

-- <data-type> list <list-name>:

-- <value>
-- <value>
-- <value>
-- ...

-- end: <list-name>

Lang:

ftd

Also make sure to use the end syntax -- end: <list-name> to mark the end of the list during initialization.

For example, to create a list of strings called weekdays, you would use the following syntax:

a list of string

-- string list weekdays:

-- string: Sunday
-- string: Monday
-- string: Tuesday
-- string: Wednesday
-- string: Thursday
-- string: Friday
-- string: Saturday

-- end: weekdays

Lang:

ftd

This creates a new variable called weekdays, which is a list of strings. The list is initialized with seven strings representing the days of the week.

By default, lists in fastn are immutable, which means that their contents cannot be changed after they are initialized. However, you can make a list mutable by prefixing it with a $ symbol, like this:

Mutable Variable

-- string list $weekdays:
-- end: $weekdays

Lang:

ftd

Let's checkout the list declaration for the more complex type data like record.

Record list

-- record person:
caption name:
body bio:

-- person list people:

-- person: Amit Upadhyay

Amit is CEO of FifthTry.

-- person: Shobhit Sharma

Shobhit is a developer at FifthTry.

-- end: people

Lang:

ftd

Here we have created a list of person objects, called it people, and created two person objects and inserted them the people list.

`ftd.ui` type as a list

You can use ftd.ui list type or children type to pass a UI component in a list.

Using ftd.ui list type

-- ftd.ui list uis:

-- ftd.text: Hello World!
color: $inherited.colors.text-strong

-- ftd.text: I love `fastn`.
color: $inherited.colors.text-strong

-- end: uis

Lang:

ftd

Using children type

-- foo:

-- ftd.text: Hello World!
color: $inherited.colors.text-strong

-- ftd.text: I love `fastn`.
color: $inherited.colors.text-strong

-- end: foo

-- component foo:
children uis:

... some code here

-- end: foo

Lang:

ftd

Accessing list items

Once you have created a list, you can access its elements using indexing or looping.

Once you have created a list, you can access its items using their index. In fastn, indexing starts at 0. Or you can use

Using `loop`

You can also access the elements of a list using a loop. In fastn, you can use the $loop$ keyword to iterate over a list. Here's an example:

-- ftd.text: $obj
$loop$: $weekdays as $obj

Lang:

ftd

Output

Sunday

Monday

Tuesday

Wednesday

Thursday

Friday

Saturday

This code will output each element of the weekdays list on a separate line. Similarly, To iterate over a uis list, you would use the following syntax:

-- obj:
$loop$: $uis as $obj

Lang:

ftd

Output

Hello World!

I love fastn.

Using index

You can access an element of a list by its index. In fastn, list indexing is zero-based, which means the first element of a list has an index of 0, the second element has an index of 1, and so on. You can use the . operator to access an element of a list by its index.

For example, to access the first item in the weekdays list, you would use the following syntax:

-- ftd.text: $weekdays.0
color: $inherited.colors.text-strong

Lang:

ftd

Output

Sunday

Similarly, To access the first component in the uis list, you would use the following syntax:

-- uis.0:

Lang:

ftd

Output

Hello World!

$processor$

A list can be created using platform provided processors:

Using $processor$

-- string list foo:
$processor$: some-list

Lang:

ftd

Here the value of the list will be provided by the some-list processor.

If we already have a list we can insert values to it using $processor$ as well:

-- string list $foo:
-- end: $foo

-- $foo:
$processor$: some-list

Lang:

ftd

list

Declaring a list

ftd.ui type as a list

Accessing list items

Using loop

Using index

$processor$

`list`

Declaring a `list`

`ftd.ui` type as a list

Using `loop`