Rust Programming: Nested Paths to Clean Up Large use Lists

Nested paths can be used to bring multiple items from the same crate or module into scope in one line. This can be useful for reducing the number of separate use statements needed, especially in larger programs.

To use a nested path, you specify the common part of the path, followed by two colons, and then curly brackets around a list of the parts of the paths that differ. For example:

Rust

use std::{cmp::Ordering, io};

This use statement brings both std::cmp::Ordering and std::io into scope.

Nested paths can be used at any level in a path. For example, the following use statement is equivalent to the previous one:

Rust

use std::{cmp::{Ordering}, io};

You can also use the self keyword in a nested path to refer to the current module. This can be useful for merging two use statements that share a subpath. For example:

Rust

use std::io::{self, Write};

This use statement is equivalent to the following two use statements:

Rust

use std::io;
use std::io::Write;

Example:

The following example shows how to use nested paths to clean up a large list of use statements:

Rust

// Before:
use std::cmp::Ordering;
use std::io;
use std::io::Read;
use std::io::Write;
use std::path::Path;
use std::path::PathBuf;

// After:
use std::{
    cmp::Ordering,
    io::{Read, Write},
    path::{Path, PathBuf},
};

The second use statement brings all of the same items into scope, but in a more concise way.

Benefits of using nested paths:

• Reduced vertical space in files
• Improved readability
• Reduced risk of errors

When to use nested paths:

Nested paths are most useful for bringing multiple items from the same crate or module into scope. They are especially useful in larger programs, where there may be many use statements.

When not to use nested paths:

Nested paths can be confusing if they are used too deeply. It is generally best to avoid using nested paths with more than two levels of nesting.

Overall, nested paths are a powerful tool that can be used to improve the readability and maintainability of Rust code.