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design_pattern-visitor.rs
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design_pattern-visitor.rs
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//! Example of design pattern inspired from Head First Design Patterns
//!
//! Tested with rust-1.29.1
//!
//! @author Eliovir <http://github.com/~eliovir>
//!
//! @license MIT license <http://www.opensource.org/licenses/mit-license.php>
//!
//! @since 2018-10-01
trait HasName {
fn name(&self) -> String;
}
trait Visitor<T> {
fn visit(&self, visitable: &T);
}
trait Visitable<T> {
fn accept(&self, visitor: &T);
}
/*
* Traits implementations
*/
// Generic Visitor
struct Inspector {
name: String
}
impl Inspector {
fn new(name: &str) -> Inspector {
Inspector{name: name.to_string()}
}
}
impl<T> Visitor<T> for Inspector where T: HasName + Visitable<Inspector> {
fn visit(&self, visitable: &T) {
println!("{} visits {}.", self.name, visitable.name());
}
}
impl HasName for Inspector {
fn name(&self) -> String {
self.name.to_string()
}
}
// First Visitable
struct Firm {
name: String
}
impl Firm {
fn new(name: &str) -> Firm {
Firm{name: name.to_string()}
}
}
impl Visitable<Inspector> for Firm {
fn accept(&self, visitor: &Inspector) {
println!("{} accepts {}.", self.name, visitor.name());
visitor.visit(self);
}
}
impl HasName for Firm {
fn name(&self) -> String {
self.name.to_string()
}
}
// 2nd Visitable
struct Foundation {
name: String
}
impl Foundation {
fn new(name: &str) -> Foundation {
Foundation{name: name.to_string()}
}
}
impl Visitable<Inspector> for Foundation {
fn accept(&self, visitor: &Inspector) {
println!("{} accepts {}", self.name, visitor.name());
visitor.visit(self);
}
}
impl HasName for Foundation {
fn name(&self) -> String {
self.name.to_string()
}
}
fn main() {
let firm = Firm::new("Big firm");
let inspector = Inspector::new("Chief");
firm.accept(&inspector);
let foundation = Foundation::new("Famous foundation");
foundation.accept(&inspector);
}