finish_fn

Applies to: structs functions methods

Overrides name, visibility and docs for the finishing function.

TIP

Don't confuse this with the member-level #[builder(finish_fn)] attribute.

Short syntax configures just the name.

#[builder(finish_fn = custom_name)]

Long syntax provides more flexibility. All keys are optional.

#[builder(
    finish_fn(
        name = custom_name,
        vis = "pub(crate)",
        doc {
            /// Custom docs
        }
    )
)]

name

The default name for the finishing function is chosen according to the following rules:

Syntax	Default
struct T	build
Associated fn T::new/builder()	build
Associated fn T::fn_name()	call
Free fn fn_name()	call

vis

The visibility must be enclosed with quotes. Use "" or "pub(self)" for private visibility.

The default visibility is the same as the visibility of the builder_type, which in turn, defaults to the visibility of the underlying struct or fn.

doc

Simple documentation is generated by default. The syntax of this attribute expects a block with doc comments.

doc {
    /// Doc comments
}

Examples

Struct

use bon::Builder;

#[derive(Builder)]
#[builder(finish_fn = assemble)] 
struct Article {
    id: u32
}

let article = Article::builder()
    .id(42)
    .assemble(); 

assert_eq!(article.id, 42);

Function

use bon::builder;

#[builder(finish_fn = send)] 
fn get_article(id: u32) -> String {
    format!("Some article with id {id}")
}

let response = get_article()
    .id(42)
    .send(); 

assert_eq!(response, "Some article with id 42");

Method

use bon::bon;

struct ArticlesClient;

#[bon]
impl ArticlesClient {
    #[builder(finish_fn = send)] 
    fn get_article(&self, id: u32) -> String {
        format!("Some article with id {id}")
    }
}

let response = ArticlesClient
    .get_article()
    .id(42)
    .send(); 

assert_eq!(response, "Some article with id 42");