Crate build_it

This crate provides a derive-macro to generate the builder pattern for a struct. The builder implementation contains a method for each field of the struct, ignoring fields with the #[skip] attribute. Each field to generate a method for must be of type Option. If any field is not of type Option, and doesn’t have the #[skip] attribute, the macro will panic.

Examples

use build_it::Builder;
#[derive(Default, Builder)]
struct MyAwesomeStruct {
    name: Option<String>,
    pub age: Option<u32>,
    #[build_it(skip)]
    address: String,

    /// The `#[build_it(rename = "new_name")]` attribute can be used to rename the builder
    /// method. In this case, the builder method will be called `new_name` instead of
    /// `renamed`:
    /// `let builder = MyAwesomeStruct::default().new_name("Alice".to_string());`
    #[build_it(rename = "new_name")]
    renamed: Option<String>,

    /// The `#[build_it(into)]` attribute can be used to allow the builder method to accept
    /// types that can be converted into the field type. In this case, the builder method will
    /// accept a `&str` instead of a `String`:
    /// `let builder = MyAwesomeStruct::default().name_into("Alice");`
    #[build_it(into)]
    name_into: Option<String>,

    #[build_it(skip)]
    // NOTE: While the `#[skip]` attribute is still supported, it is deprecated in favor of
    // the `#[build_it(skip)]` attribute.
    pub phone: Option<String>,
}
let builder = MyAwesomeStruct::default()
    .name("Alice".to_string())
    .age(42);
    // Note that `address` and `phone` do not have builder methods because of the #[skip]
    // attribute.
assert_eq!(builder.name, Some("Alice".to_string()));
assert_eq!(builder.age, Some(42));

// These fields are skipped, so they're value will still be the default value.
assert_eq!(builder.address, String::default());
assert_eq!(builder.phone, None);

The generated builder methods will also display the field’s documentation:

use build_it::Builder;
#[derive(Default, Builder)]
struct MyAwesomeStruct {
    /// Name of the person
    name: Option<String>,
    /// Age of the person
    age: Option<u32>,
}

This will generate the following builder methods:

impl MyAwesomeStruct {
   /// Name of the person
    pub fn name(mut self, name: String) -> Self {
        self.name = Some(name);
        self
    }
    /// Age of the person
    pub fn age(mut self, age: u32) -> Self {
        self.age = Some(age);
        self
    }
}

Derive Macros

Builder

Derive the builder pattern for a struct.