Rust by Example

11 Attributes

An attribute is metadata applied to some module, crate or item. This metadata can be used to/for:

When attributes apply to a whole crate, their syntax is #![crate_attribute], and when they apply to a module or item, the syntax is #[item_attribute] (notice the missing bang !).

Attributes can take arguments with different syntaxes:

  • #[attribute = "value"]
  • #[attribute(key = "value")]
  • #[attribute(value)]