28 lines
571 B
Plaintext
28 lines
571 B
Plaintext
trait Thingable {
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fn thing(&self) -> &str;
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}
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struct Delegator<T>(Option<T>);
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struct Delegate {}
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impl Thingable for Delegate {
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fn thing(&self) -> &'static str {
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"Delegate implementation"
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}
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}
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impl<T: Thingable> Thingable for Delegator<T> {
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fn thing(&self) -> &str {
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self.0.as_ref().map(|d| d.thing()).unwrap_or("Default implmementation")
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}
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}
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fn main() {
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let d: Delegator<Delegate> = Delegator(None);
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println!("{}", d.thing());
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let d: Delegator<Delegate> = Delegator(Some(Delegate {}));
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println!("{}", d.thing());
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}
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