FmtOr

一个易于格式化缺失值的扩展特质。

示例

use fmtor::FmtOr;

let maybe_box: Option<Box<()>> = None;

println!("The box is at: {:p}", maybe_box.fmt_or("Null"));

打印： 盒子在：Null

lib.rs:

fmtor

查看 FmtOr 特质。

示例

use fmtor::FmtOr;

let maybe_ref: Option<&()> = None;

assert_eq!(
    "Null",
    format!("{:p}", maybe_ref.fmt_or("Null"))
);

use fmtor::FmtOr;

struct NullMarker;
impl std::fmt::Display for NullMarker {
    fn fmt(&self, out: &mut std::fmt::Formatter) -> std::fmt::Result {
        out.write_str("Null")
    }    
}
let maybe_ref: Option<&u32> = None;

assert_eq!(
    "Null",
    format!("{:x}", maybe_ref.fmt_or(NullMarker))
);