Struct rocket::request::Form

pub struct Form<'f, T: FromForm<'f> + 'f> { /* fields omitted */ }

A FromData type for parsing FromForm types.

This type implements the FromData trait. It provides a generic means to parse arbitrary structures from incoming form data.

Usage

This type can be used with any type that implements the FromForm trait. The trait can be automatically derived; see the FromForm documentation for more information on deriving or implementing the trait.

Because Form implement FromData, it can be used directly as a target of the data = "<param>" route parameter. For instance, if some structure of type T implements the FromForm trait, an incoming form can be automatically parsed into the T structure with the following route and handler:

#[post("/form_submit", data = "<param>")]
fn submit(form: Form<T>) ... { ... }

To preserve memory safety, if the underlying structure type contains references into form data, the type can only be borrowed via the get or get_mut methods. Otherwise, the parsed structure can be retrieved with the into_inner method.

With References

The simplest data structure with a reference into form data looks like this:

#[derive(FromForm)]
struct UserInput<'f> {
    value: &'f str
}

This corresponds to a form with a single field named value that should be a string. A handler for this type can be written as:

#[post("/submit", data = "<user_input>")]
fn submit_task<'r>(user_input: Form<'r, UserInput<'r>>) -> String {
    format!("Your value: {}", user_input.get().value)
}

Note that the `r lifetime is used twice in the handler's signature: this is necessary to tie the lifetime of the structure to the lifetime of the request data.

Without References

The owned analog of the UserInput type above is:

#[derive(FromForm)]
struct OwnedUserInput {
    value: String
}

The handler is written similarly:

#[post("/submit", data = "<user_input>")]
fn submit_task(user_input: Form<OwnedUserInput>) -> String {
    let input: OwnedUserInput = user_input.into_inner();
    format!("Your value: {}", input.value)
}

Note that no lifetime annotations are required: Rust is able to infer the lifetime as `static. Because the lifetime is `static, the into_inner method can be used to directly retrieve the parsed value.

Performance and Correctness Considerations

Whether you should use a str or String in your FromForm type depends on your use case. The primary question to answer is: Can the input contain characters that must be URL encoded? Note that this includes commmon characters such as spaces. If so, then you must use String, whose FromFormValue implementation deserializes the URL encoded string for you. Because the str references will refer directly to the underlying form data, they will be raw and URL encoded.

If your string values will not contain URL encoded characters, using str will result in fewer allocation and is thus spreferred.

Methods

impl<'f, T: FromForm<'f> + 'f> Form<'f, T>

fn get(&'f self) -> &'f T

Immutably borrow the parsed type.

fn get_mut(&'f mut self) -> &'f mut T

Mutably borrow the parsed type.

fn raw_form_string(&self) -> &str

Returns the raw form string that was used to parse the encapsulated object.

impl<'f, T: FromForm<'f> + 'static> Form<'f, T>

fn into_inner(self) -> T

Consume this object and move out the parsed object.

Trait Implementations

impl<'f, T: FromForm<'f> + Debug + 'f> Debug for Form<'f, T>

fn fmt(&self, f: &mut Formatter) -> Result

Formats the value using the given formatter.

impl<'f, T: FromForm<'f>> FromData for Form<'f, T> where T::Error: Debug

Parses a Form from incoming form data.

If the content type of the request data is not application/x-www-form-urlencoded, Forwards the request. If the form data cannot be parsed into a T, a Failure with status code UnprocessableEntity is returned. If the form string is malformed, a Failure with status code BadRequest is returned. Finally, if reading the incoming stream fails, returns a Failure with status code InternalServerError. In all failure cases, the raw form string is returned if it was able to be retrieved from the incoming stream.

All relevant warnings and errors are written to the console in Rocket logging format.

type Error = Option<String>

The raw form string, if it was able to be retrieved from the request.

fn from_data(request: &Request, data: Data) -> Outcome<Self, Self::Error>

Parses an instance of Self from the incoming request body data.