Gabriel N. gary17
gary17
/ DowncastGenericStruct.rs
Last active
May 28, 2022 18:56
Downcasting from a trait object to a generic struct that implements the trait.
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| trait A { | |
| fn as_any_mut(&mut self) -> &mut dyn std::any::Any; | |
| } | |
| struct B<T> { | |
| _unused: T | |
| } | |
| impl<T: 'static> A for B<T> { // static, else: "the parameter type `T` may not live long enough" | |
| fn as_any_mut(&mut self) -> &mut dyn std::any::Any { | |
| self | |
| } |
gary17
/ UnwrapOrEmpty.rs
Created
May 28, 2022 16:33
Provide a default for Option<T> unwrap() through a reference to a static instance of an object, e.g. for HashMap::<&str, String>.
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| trait UnwrapOrEmpty<'a> { | |
| fn unwrap_or_empty(&self) -> &'a String; | |
| } | |
| impl<'a> UnwrapOrEmpty<'a> for Option<&'a String> { | |
| fn unwrap_or_empty(&self) -> &'a String { | |
| self.unwrap_or_else(||{ // use a closure | |
| static DEFAULT: String = String::new(); // declare a static String | |
| &DEFAULT // return a reference to a String to match HashMap::get() | |
| }) | |
| } |