diff --git a/src/doc/book/structs.md b/src/doc/book/structs.md index cfd00cf997e0b..dcf74cbb0a7c4 100644 --- a/src/doc/book/structs.md +++ b/src/doc/book/structs.md @@ -117,6 +117,30 @@ fn main() { } ``` +Initialization of a data structure (struct, enum, union) can be simplified if +fields of the data structure are initialized with variables which has same +names as the fields. + +``` +#![feature(field_init_shorthand)] + +#[derive(Debug)] +struct Person<'a> { + name: &'a str, + age: u8 +} + +fn main() { + // Create struct with field init shorthand + let name = "Peter"; + let age = 27; + let peter = Person { name, age }; + + // Print debug struct + println!("{:?}", peter); +} +``` + # Update syntax A `struct` can include `..` to indicate that you want to use a copy of some diff --git a/src/doc/reference.md b/src/doc/reference.md index dfdfe32882028..8139a712bddb2 100644 --- a/src/doc/reference.md +++ b/src/doc/reference.md @@ -2757,6 +2757,28 @@ let base = Point3d {x: 1, y: 2, z: 3}; Point3d {y: 0, z: 10, .. base}; ``` +#### Struct field init shorthand + +When initializing a data structure (struct, enum, union) with named fields, +allow writing `fieldname` as a shorthand for `fieldname: fieldname`. This +allows a compact syntax for initialization, with less duplication. + +In the initializer for a `struct` with named fields, a `union` with named +fields, or an enum variant with named fields, accept an identifier `field` as a +shorthand for `field: field`. + +Example: + +``` +# #![feature(field_init_shorthand)] +# struct Point3d { x: i32, y: i32, z: i32 } +# let x = 0; +# let y_value = 0; +# let z = 0; +Point3d { x: x, y: y_value, z: z }; +Point3d { x, y: y_value, z }; +``` + ### Block expressions A _block expression_ is similar to a module in terms of the declarations that