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Overview

Design

Why Use `fastn` for Your Next Frontend?

`ftd.rive` (animation)

Container Root Attributes

`import`

Using export/exposing

Functions

Built-in Functions

Built-in Rive Functions

Built-in Local Storage Functions

Built-in Variables

`ftd` Events

Rive Events

Use color scheme package

How to make page responsive

Using JS

JS in function

Web Component

Create `fastn` package

Same argument & attribute types

`record`

`fastn` supports `record` types. These are also called `struct` in some languages.

Declaring a `record`

Before a record can be used it must be declared using the `record` syntax:

Declaring a Person record

-- record person:
caption name:
integer age:
optional body bio:

Lang:

ftd

Here we are creating a record. The name of the record is `person`. It has three fields: `name`, `age` and `bio`.

Declaring a Company record

-- record company:
caption name:
person list employees:

Lang:

ftd

In this case, the name of the record is `company`. It has two fields: caption `name` and list of `employees` of `person` type.

Declaring a `record` with default values

Sometimes, the programmer might want to provide default values to the record fields, in case if he/she doesn't specify those during initialization.

Declaring a Person record with default field values

-- record person:
caption name: Undefined
integer age:
optional body bio: Not specified

;; << Alternative way >>
-- record person:
caption name: Undefined
integer age:

-- optional body person.bio:

No bio is specified for this person.

Lang:

ftd

Declaring a Company record with default field values

-- record company:
string name: FifthTry

-- person list company.employees:

-- person:
name: Arpita
age: 22

-- person:
name: Abrar
age: 24

-- end: company.employees

Lang:

ftd

Field Types

Fields can be either one of the [built-in types](ftd/built-in-types/), another type like a [`record`](ftd/record/) or [`or-type`](ftd/or-type/).

Record Variable

A [variable](ftd/variables/) can be created with type `record`:

-- person john-snow: John Snow
age: 14

Lang:

ftd

Here we have created a new variable of type `person`, called it `amitu`, and the value of `name`, since its declared as `caption` in the record definition, is read from the "caption" area, and `age` is read from the "header". Note that we have not passed `bio`, since `bio` is declared as `optional body`, so it's not a problem. Had it been just `body` the above would not have been valid.

Record Field Update Syntax

The field which needs to be updated has to be mutable before updating its value. An individual field of a record can be updated using a syntax like this:

-- $john-snow.age: 15

-- person $john-snow: John Snow
$age: 14

Lang:

ftd

Here we have used `-- $john-snow.age: 15` to update a single field of a record. This also works if the field is a list:

-- record person:
caption name:
string list alias:

-- person $john-snow: John Snow

-- $john-snow.alias:

-- string: Aegon Targaryen
-- string: Lord Crow
-- string: The White Wolf
-- string: The Prince That Was Promised

-- end: $john-snow.alias

Lang:

ftd

Reading A Record From Rust

A `record` in `fastn` is equivalent of a `struct` in Rust.

Rust Type

To read the above `.ftd` file from Rust you will have to first create a `struct` in Rust that is compatible with our `person` definition:

#[derive(serde::Deserialize)]
struct Person {
name: String,
age: i32,
bio: Option<String>,
}

Lang:

For each field in `person` record, we have a corresponding field in our `Person` `struct`. Note that we used `age` as i32, but it could have been any type that can be deserialised from [JSON Number](https://docs.serde.rs/serde_json/struct.Number.html) since `fastn` integer is converted to `JSON Number`.

Support `fastn`!

Enjoying `fastn`? Please consider giving us a star ⭐️ on [GitHub](https://github.com/fastn-stack/fastn) to show your support!

[⭐️](https://github.com/fastn-stack/fastn)

Getting Help

Have a question or need help? Visit our [GitHub Q&A discussion](https://github.com/fastn-stack/fastn/discussions/categories/q-a) to get answers and subscribe to it to stay tuned. Join our [Discord](https://discord.gg/a7eBUeutWD) channel and share your thoughts, suggestion, question etc. Connect with our [community](/community/)!

[💻️](/community/)

Found an issue?

If you find some issue, please visit our [GitHub issues](https://github.com/fastn-stack/fastn/issues) to tell us about it.

Quick links:

- [Install `fastn`](install/) - [Create `fastn` package](create-fastn-package/) - [Expander Crash Course](expander/) - [Syntax Highlighting in Sublime Text](/sublime/)

Join us

We welcome you to join our [Discord](https://discord.gg/a7eBUeutWD) community today. We are trying to create the language for human beings and we do not believe it would be possible without your support. We would love to hear from you.