armanriazi•rust•concept•dynamic•dispatch

ArmanRiazi answered on June 5, 2022 Popularity 2/10 Helpfulness 1/10

answer armanriazi•rust•concept•dynamic•dispatch

armanriazi•rust•concept•dynamic•dispatch

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The code that results from monomorphization is doing static dispatch, which is when the compiler knows what method you’re calling at compile time.
This is opposed to dynamic dispatch, which is when the compiler can’t tell at compile time which method you’re calling.
In dynamic dispatch cases, the compiler emits code that at runtime will figure out which method to call.
When we use trait objects, Rust must use dynamic dispatch. The compiler doesn’t know all the types that might be used with the code that is using trait objects,
so it doesn’t know which method implemented on which type to call. Instead, at runtime, Rust uses the pointers inside the trait object to know which method to call. There is a runtime cost when this lookup happens that doesn’t occur with static dispatch. Dynamic dispatch also prevents the compiler from choosing to inline a method’s code, which in turn prevents some optimizations.
pub trait Draw {
    fn draw(&self);
}

pub struct Screen {
    pub components: Vec<Box<dyn Draw>>,
}

Popularity 2/10 Helpfulness 1/10 Language rust

Source: github.com

Tags: rust

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Contributed on Jun 05 2022

ArmanRiazi

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armanriazi•rust•concept•dynamic•dispatch

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