A Rust struct groups named fields into one logical value. It is similar to a class, but does not support inheritance. Start with an artwork that has one field: `name: String`. A value supplies that field when it is created; `to_string()` converts the name’s string literal into a `String`. section 2.1
Listing 2.2 Struct representing an artwork
struct Artwork {
name: String,
}
fn main() {
let art1 = Artwork {
name: "Boy with Apple".to_string()
};
}
The `Artwork` declaration names the field and its type; the value created in `main` supplies the field’s value. section 2.1
Passing an `Artwork` to `admire_art(art: Artwork)` moves that value into the function. Trying to pass the same variable again produces a “use of moved value” error. The grouped fields make a convenient function argument, but ownership still matters. section 2.1
The same pattern scales to external data:
- For JSON with a string `name` and numeric `value`, define `struct Data { name: String, value: i32 }`. Derive `serde::Deserialize`, then give the parsed result the type `Data` when calling `serde_json::from_str`. section 6.3
- For an XML search feed, define related `Feed`, `Entry`, and `Author` structs. Fields include `Vec<Entry>` and `Vec<Author>`; the fetched XML is parsed into a `Feed`. section 9.3.1
When the data does not match
If JSON supplies a string for `name` but `Data` declares `name: i32`, deserialization reports a type error. In the shown code, calling `unwrap()` on that error causes a panic. A struct’s field types therefore describe what the parser expects, not what arbitrary input will contain. section 6.3
