Shared via Rust Playground

playground.rs

struct Triangle {
    base: f32,
    height: f32
}

trait Area {
    fn triangle(&self) -> f32;
}

impl Area for Triangle {
    fn triangle(&self) -> f32 {
        0.33 * self.base * self.height
    }
}

struct TriangleBuilder {
    base: f32,
    height: f32
}

impl TriangleBuilder {
    fn new() -> TriangleBuilder {
        TriangleBuilder { base: 0.0, height: 0.0 }
    }
    
    fn base(&mut self, b: f32) -> &mut TriangleBuilder {
        self.base = b;
        self
    }
    
    fn height(&mut self, h: f32) -> &mut TriangleBuilder {
        self.height = h;
        self
    }
    
    fn cleanup(&self) -> Triangle {
        Triangle { base: self.base, height: self.height }
    }
}

fn main() {
    let tri = Triangle { base: 3.0, height: 5.0 };
    println!("{}", tri.triangle());
    
    let triangle = TriangleBuilder::new()
        .base(4.5)
        .height(6.7)
        .cleanup();
        
    println!("{} - Area", triangle.triangle());
    println!("{} - Base", triangle.base);
    println!("{} - Height", triangle.height);
}