foo.rs

use std::default::Default;

const DEFAULT_PER_PAGE: i64 = 10;
const DEFAULT_PAGE: i64 = 1;

#[derive(FromForm)]
pub struct Pagination {
    per_page: Option<i64>,
    page: Option<i64>
}

impl Default for Pagination {
    fn default() -> Self {
        Self {
            per_page: Some(DEFAULT_PER_PAGE),
            page: Some(DEFAULT_PAGE)
        }
    }
}

impl Pagination {
    pub fn get_per_page(&self) -> i64 {
        self.per_page.unwrap_or(DEFAULT_PER_PAGE)
    }

    pub fn get_page(&self) -> i64 {
        self.page.unwrap_or(DEFAULT_PAGE)
    }
}

#[get("/posts?<pagination>", format = "application/json")]
fn index_paginated(db: State<Db>, pagination: Pagination) -> EndpointResult<JSON<Value>> {
    let results = published_posts(&*db, Some(&pagination))?;

    Ok(JSON(json!(results)))
}

// I would like to do:
#[get("/posts?<pagination>", format = "application/json")]
fn index_paginated(db: State<Db>, pagination: &Pagination) -> EndpointResult<JSON<Value>> {
    let results = published_posts(&*db, Some(pagination))?;

    Ok(JSON(json!(results)))
}

// But rust does not like it

error[E0277]: the trait bound `&endpoints::pagination::Pagination: rocket::request::FromForm<'_>` is not satisfied
  --> src/endpoints/api_v1/posts.rs:29:1
   |
29 | #[get("/posts?<pagination>", format = "application/json")]
   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `rocket::request::FromForm<'_>` is not implemented for `&endpoints::pagination::Pagination`
   |
   = help: the following implementations were found:
             <endpoints::pagination::Pagination as rocket::request::FromForm<'rocket>>
   = note: required by `rocket::request::FromForm::from_form_items`