overview.toml

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# Panels: displayed in a tabbed arrangement.
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[[panels]]
name = "Routing"
checked = true
content = '''
Rocket's main task is to route incoming requests to the appropriate request
handler using your application's declared routes. Routes are declared using
Rocket's _route_ attributes. The attribute describes the requests that match the
route. The attribute is placed on top of a function that is the request handler
for that route.

As an example, consider the simple route below:

```rust
#[get("/")]
fn index() -> &'static str {
   "Hello, world!"
}
```

This route, named `index`, will match against incoming HTTP `GET` requests to
the `/` path, the index. The request handler returns a string. Rocket will use
the string as the body of a fully formed HTTP response.
'''

[[panels]]
name = "Dynamic Params"
content = '''
Rocket allows you to interpret segments of a request path dynamically. To
illustrate, let's use the following route:

```rust
#[get("/hello/<name>/<age>")]
fn hello(name: String, age: u8) -> String {
    format!("Hello, {} year old named {}!", age, name)
}
```

The `hello` route above matches two dynamic path segments declared inside
brackets in the path: `<name>` and `<age>`. _Dynamic_ means that the segment can
be _any_ value the end-user desires.

Each dynamic parameter (`name` and `age`) must have a type, here `&str` and
`u8`, respectively. Rocket will attempt to parse the string in the parameter's
position in the path into that type. The route will only be called if parsing
succeeds. To parse the string, Rocket uses the
[FromParam](@api/rocket/request/trait.FromParam.html) trait,
which you can implement for your own types!
'''

[[panels]]
name = "Handling Data"
content = '''
Request body data is handled in a special way in Rocket: via the
[FromData](@api/rocket/data/trait.FromData.html) trait. Any type that implements
`FromData` can be derived from incoming body data. To tell Rocket that you're
expecting request body data, the `data` route argument is used with the name of
the parameter in the request handler:

```rust
#[post("/login", data = "<user_form>")]
fn login(user_form: Form<UserLogin>) -> String {
   format!("Hello, {}!", user_form.name)
}
```

The `login` route above says that it expects `data` of type `Form<UserLogin>` in
the `user_form` parameter. The [Form](@api/rocket/request/struct.Form.html) type
is a built-in Rocket type that knows how to parse web forms into structures.
Rocket will automatically attempt to parse the request body into the `Form` and
call the `login` handler if parsing succeeds. Other built-in `FromData` types
include [`Data`](@api/rocket/struct.Data.html),
[`Json`](@api/rocket_contrib/json/struct.Json.html), and
[`Flash`](@api/rocket/response/struct.Flash.html).
'''

[[panels]]
name = "Request Guards"
content = '''
In addition to dynamic path and data parameters, request handlers can also
contain a third type of parameter: _request guards_. Request guards aren't
declared in the route attribute, and any number of them can appear in the
request handler signature.

Request guards _protect_ the handler from running unless some set of conditions
are met by the incoming request metadata. For instance, if you are writing an
API that requires sensitive calls to be accompanied by an API key in the request
header, Rocket can protect those calls via a custom `ApiKey` request guard:

```rust
#[get("/sensitive")]
fn sensitive(key: ApiKey) { ... }
```

`ApiKey` protects the `sensitive` handler from running incorrectly. In order for
Rocket to call the `sensitive` handler, the `ApiKey` type needs to be derived
through a [`FromRequest`](@api/rocket/request/trait.FromRequest.html)
implementation, which in this case, validates the API key header. Request guards
are a powerful and unique Rocket concept; they centralize application policy and
invariants through types.
'''

[[panels]]
name = "Responders"
content = '''
The return type of a request handler can be any type that implements
[Responder](@api/rocket/response/trait.Responder.html):

```rust
#[get("/")]
fn route() -> T { ... }
```

Above, T must implement `Responder`. Rocket implements `Responder` for many of
the standard library types including `&str`, `String`, `File`, `Option`, and
`Result`. Rocket also implements custom responders such as
[Redirect](@api/rocket/response/struct.Redirect.html),
[Flash](@api/rocket/response/struct.Flash.html), and
[Template](@api/rocket_contrib/templates/struct.Template.html).

The task of a `Responder` is to generate a
[`Response`](@api/rocket/response/struct.Response.html), if possible.
`Responder`s can fail with a status code. When they do, Rocket calls the
corresponding error catcher, a `catch` route, which can be declared as follows:

```rust
#[catch(404)]
fn not_found() -> T { ... }
```
'''

[[panels]]
name = "Launching"
content = '''
Launching a Rocket application is the funnest part! For Rocket to begin
dispatching requests to routes, routes need to be _mounted_. After mounting, the
application needs to be _launched_. These two steps, usually done in a `rocket`
function, look like:

```rust
#[launch]
fn rocket() -> _ {
    rocket::build().mount("/base", routes![index, another])
}
```

The `mount` call takes a base path and a set of routes via the `routes!` macro.
The base path (`/base` above) is prepended to the path of every route in the
list. This namespaces the routes, allowing for composition. The `#[launch]`
attribute creates a `main` function that starts the server. In development,
Rocket prints useful information to the console to let you know everything is
okay.

```sh
🚀  Rocket has launched from http://localhost:8000
```
'''

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# Steps to "How Rocket Works"
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[[steps]]
name = "Validation"
color = "blue"
content = '''
First, Rocket validates a matching request by ensuring that all of the types in
a given handler can be derived from the incoming request. If the types cannot be
derived, the request is forwarded to the next matching route until a route’s
types validate or there are no more routes to try. If all routes fail, a
customizable **404** error is returned.

```rust
#[post("/user", data = "<new_user>")]
fn new_user(admin: AdminUser, new_user: Form<User>) -> T {
   ...
}
```

For the `new_user` handler above to be called, the following conditions must
hold:

  * The request method must be `POST`.
  * The request path must be `/user`.
  * The request must contain `data` in its body.
  * The request metadata must authenticate an `AdminUser`.
  * The request body must be a form that parses into a `User` struct.
'''

[[steps]]
name = "Processing"
color = "purple"
content = '''
Next, the request is processed by an arbitrary handler. This is where most of
the business logic in an application resides, and the part of your applications
you’ll likely spend the most time writing. In Rocket, handlers are simply
functions - that’s it! The only caveat is that the function’s return type must
implement the `Responder` trait. The `new_user` function above is an example of
a handler.
'''

[[steps]]
name = "Response"
color = "red"
content = '''
Finally, Rocket responds to the client by transforming the return value of the
handler into an HTTP response. The HTTP response generated from the returned
value depends on the type’s specific `Responder` trait implementation.

```rust
fn route() -> T { ... }
```

If the function above is used as a handler, for instance, then the type `T` must
implement `Responder`. Rocket provides many useful responder types out of the
box. They include:

  * `Json<T>`: Serializes the structure T into JSON and returns it to
    the client.
  * `Template`: Renders a template file and returns it to the client.
  * `Redirect`: Returns a properly formatted HTTP redirect.
  * `NamedFile`: Streams a given file to the client with the
    Content-Type taken from the file’s extension.
  * `Stream`: Streams data to the client from an arbitrary `Read` value.
  * Many Primitive Types: `String`, `&str`, `File`, `Option`, `Result`, and
    others all implement the `Responder` trait.
'''