python;gutter:true;</p>
<h1>[macro_use]</h1>
<p>extern crate mopa;</p>
<p>struct Bear {
// This might be a pretty fat bear.</p>
<pre><code>fatness: u16,
</code></pre>
<p>}</p>
<p>impl Bear {
fn eat(&mut self, person: Box) {
self.fatness = (self.fatness as i16 + person.weight()) as u16;
}
}</p>
<p>trait Person: mopa::Any {
fn panic(&self);
fn yell(&self) { println!("Argh!"); }
fn sleep(&self);
fn weight(&self) -> i16;
}</p>
<p>mopafy!(Person);</p>
<p>struct Benny {
// (Benny is not a superhero. He can't carry more than 256kg of food at once.)
kilograms_of_food: u8,
}</p>
<p>impl Person for Benny {
fn panic(&self) { self.yell() }
fn sleep(&self) { /<em> ... </em>/ }
fn weight(&self) -> i16 {
// Who's trying to find out? I'm scared!</p>
<pre><code> self.yell();
self.kilograms_of_food as i16 + 60
}
</code></pre>
<p>}</p>
<p>struct Chris;</p>
<p>impl Chris {
// Normal people wouldn't be brave enough to hit a bear but Chris might.</p>
<pre><code>fn hit(&self, bear: &mut Bear) {
println!("Chris hits the bear! How brave! (Or maybe stupid?)");
// Meh, boundary conditions, what use are they in examples?
// Chris clearly hits quite hard. Poor bear.
bear.fatness -= 1;
}
</code></pre>
<p>}</p>
<p>impl Person for Chris {
fn panic(&self) { /<em> ... </em>/ }
fn sleep(&self) { /<em> ... </em>/ }
fn weight(&self) -> i16 { -5 /<em> antigravity device! cool! </em>/ }
}</p>
<p>fn simulate_simulation(person: Box, bear: &mut Bear) {
if person.is::() {
// None of the others do, but Benny knows this particular
// bear by reputation and he's <em>really</em> going to be worried.</p>
<pre><code> person.yell()
}
// If it happens to be Chris, he'll hit the bear.
person.downcast_ref::().map(|chris| chris.hit(bear));
bear.eat(person);
</code></pre>
<p>}</p>
<p>fn main() {
let mut bear = Bear { fatness: 10 };
simulate_simulation(Box::new(Benny { kilograms_of_food: 5 }), &mut bear);
simulate_simulation(Box::new(Chris), &mut bear);
}
Original: https://www.cnblogs.com/pythonClub/p/16518377.html
Author: CrossPython
Title: rust mopa
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