Rust 格式/Formatting
我们已经看到，通过指定的格式格式字符串：
-
format!("{}", foo)%uA0->%uA0"3735928559" -
format!("0x{:X}", foo)%uA0->%uA0"0xDEADBEEF" -
format!("0o{:o}", foo)%uA0->%uA0"0o33653337357"
相同的变量(foo)可以格式化成不同形式，具体取决于使用哪个参数类型:%uA0X%uA0vso%uA0和%uA0unspecified.
这种格式化功能是通过特征来实现，并且每一个参数的类型有各个特征。最常见的格式特征是%uA0Display,%uA0它处理参数类型的未指定情况，例如：%uA0{}%uA0
use std::fmt::{self, Formatter, Display}
struct City {
name: &&aposstatic str,
// Latitude
lat: f32,
// Longitude
lon: f32,
}
impl Display for City {
// `f` is a buffer, this method must write the formatted string into it
fn fmt(&self, f: &mut Formatter) -> fmt::Result {
let lat_c = if self.lat >= 0.0 { &aposN&apos } else { &aposS&apos }
let lon_c = if self.lon >= 0.0 { &aposE&apos } else { &aposW&apos }
// `write!` is like `format!`, but it will write the formatted string
// into a buffer (the first argument)
write!(f, "{}: {:.3}%uB0{} {:.3}%uB0{}",
self.name, self.lat.abs(), lat_c, self.lon.abs(), lon_c)
}
}
fn main() {
for city in [
City { name: "Dublin", lat: 53.347778, lon: -6.259722 },
City { name: "Oslo", lat: 59.95, lon: 10.75 },
City { name: "Vancouver", lat: 49.25, lon: -123.1 },
].iter() {
println!("{}", *city)
}
}
下面是格式化特征和它们各自的参数类型的完整列表：
-
unspecified%uA0->%uA0
Display -
?%uA0->%uA0Debug -
o%uA0->%uA0Octal -
x%uA0->%uA0LowerHex -
X%uA0->%uA0UpperHex -
p%uA0->%uA0Pointer -
b%uA0->%uA0Binary -
e%uA0->%uA0LowerExp -
E%uA0->%uA0UpperExp