Rust類型轉換 - 別名

Rust類型轉換 - 別名

type語句聲明可以以現有類型被用來給一個新的名字。類型必須有 CamelCase 名稱, 或者編譯器會提出警告。例外(異常)是原始類型: usize,f32, 等.

// `NanoSecond` is a new name for `u64`.
type NanoSecond = u64;
type Inch = u64;

// Use an attribute to silence warning.
#[allow(non_camel_case_types)]
type u64_t = u64;
// TODO ^ Try removing the attribute

// Use an attribute to silence warnings
#[allow(trivial_numeric_casts)]
fn main() {
// `NanoSecond` = `Inch` = `u64_t` = `u64`.
let nanoseconds: NanoSecond = 5 as u64_t;
let inches: Inch = 2 as u64_t;

// Note that type aliases \*don't\* provide any extra type safety, because
// aliases are \*not\* new types
println!("{} nanoseconds + {} inches = {} unit?",
         nanoseconds,
         inches,
         nanoseconds + inches);

}

使用別名主要是減少輸入;例如 IoResult 是類型Result<T, IoError> 的別名.

另請參見:

屬性

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