在这篇简短的文章中，我描述并命名了构建器模式的表亲——builder lite。
与使用单独的构建器对象的传统构建器不同，构建器精简版重用对象本身来提供构建器功能。
这是一个builder lite说明性示例
pub struct Shape {
position: Vec3,
geometry: Geometry,
material: Option<Material>,
}
impl Shape {
pub fn new(geometry: Geometry) -> Shape {
Shape {
position: Vec3::default(),
geometry,
material: None,
}
}
pub fn with_position(mut self, position: Vec3) -> Shape {
self.position = position;
self
}
pub fn with_material(mut self, material: Material) -> Shape {
self.material = Some(material);
self
}
}
// Call site
let shape = Shape::new(Geometry::Sphere::with_radius(1))
.with_position(Vec3(0, 9, 2))
.with_material(Material::SolidColor(Color::Red));
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builder-lite 的主要好处是它是new方法的增量、零成本演进。因此，它在代码快速发展、方向不确定的情况下特别有用。也就是说，在构建应用程序而不是库时适用。
相比之下，完全的构建器builder在定义站点要冗长得多，并且需要在调用站点进行一些额外的调用，如下：
pub struct Shape {
position: Vec3,
geometry: Geometry,
material: Option<Material>,
}
pub struct ShapeBuilder {
position: Option<Vec3>,
geometry: Option<Geometry>,
texture: Option<Texture>,
}
impl Shape {
pub fn builder() -> ShapeBuilder { ... }
}
impl ShapeBuilder {
pub fn position(&mut self, position: Vec3) -> &mut Self { ... }
pub fn geometry(&mut self, geometry: Geometry) -> &mut Self { ... }
pub fn material(&mut self, material: Material) -> &mut Self { ... }
pub fn build(&self) -> Shape { ... }
}
// Call site
let shape = Shape::builder()
.position(Vec3(9, 2))
.geometry(Geometry::Sphere::with_radius(1))
.material(Material::SolidColor(Color::Red))
.build();
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