Implementing the strategy pattern in Rust

code review
5

This is what I came up with: Playground

It uses dynamic dispatch, but you could make it generic I guess. The advantage is that the strategy can be selected at runtime, but the disadvantage is that the implementation trait must be object safe.

The main idea is to use a struct instead of a trait for the TextFormatter:

// A struct that can format something with different strategies
pub struct TextFormatter<'a> {
    strategy: &'a dyn TextFormatterImpl,
}

The trait implementing the strategies is private, so it can't be implemented in other modules:

trait TextFormatterImpl {
    fn bold_impl(&self, f: &mut Formatter<'_>, value: &dyn Display) -> fmt::Result;

    fn strike_impl(&self, f: &mut Formatter<'_>, value: &dyn Display) -> fmt::Result;
}

EDIT: Here's a Playground using generics.

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