Video address
Headline address:https://www.ixigua.com/i677586170644791348…
Station B address:https://www.bilibili.com/video/av81202308/
Source address
GitHub address:https://github.com/anonymousGiga/learn_rus…
Explanation content
1. Type alias
example:
type Kilometers = i32;
let x: i32 = 5;
let y: Kilometers = 5;
println!("x + y = {}", x + y);
Note: in the example, kilmeters is a synonym for I32. Values of the kilometers type are treated exactly as I32 types.
The main purpose of type aliases is to reduce duplication.
(1) Consider the following types:
Box<dyn Fn() + Send + 'static>
Such as code:
let f: Box<dyn Fn() + Send + 'static> = Box::new(|| println!("hi"));
fn takes_long_type(f: Box<dyn Fn() + Send + 'static>) {
// --snip--
}
fn returns_long_type() -> Box<dyn Fn() + Send + 'static> {
// --snip--
}
Use alias, code:
type Thunk = Box<dyn Fn() + Send + 'static>;
let f: Thunk = Box::new(|| println!("hi"));
fn takes_long_type(f: Thunk) {
// --snip--
}
fn returns_long_type() -> Thunk {
// --snip--
}
(2) Consider the following examples:
use std::io::Error; // The STD:: IO:: error structure in the standard library represents all possible I / O errors
use std::fmt;
pub trait Write {
fn write(&mut self, buf: &[u8]) -> Result<usize, Error>;
fn flush(&mut self) -> Result<(), Error>;
fn write_all(&mut self, buf: &[u8]) -> Result<(), Error>;
fn write_fmt(&mut self, fmt: fmt::Arguments) -> Result<(), Error>;
}
Add the following type alias declaration:
type Result<T> = std::result::Result<T, std::io::Error>;// STD:: IO:: error is placed in result < T, E >
The code can become:
pub trait Write {
fn write(&mut self, buf: &[u8]) -> Result<usize>;
fn flush(&mut self) -> Result<()>;
fn write_all(&mut self, buf: &[u8]) -> Result<()>;
fn write_fmt(&mut self, fmt: Arguments) -> Result<()>;
}
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