log-custom-logger.zh.md

使用自定义记录器，记录消息

[![log-badge]][log] [![cat-debugging-badge]][cat-debugging]

实现一个自定义记录器ConsoleLogger，它打印到 stdout。为了使用记录的宏，ConsoleLogger实现log::Log trait，那么log::set_logger就能安装它了。

#[macro_use]
extern crate log;

use log::{Record, Level, Metadata, LevelFilter, SetLoggerError};

static CONSOLE_LOGGER: ConsoleLogger = ConsoleLogger;

struct ConsoleLogger;

impl log::Log for ConsoleLogger {
  fn enabled(&self, metadata: &Metadata) -> bool {
     metadata.level() <= Level::Info
    }

    fn log(&self, record: &Record) {
        if self.enabled(record.metadata()) {
            println!("Rust says: {} - {}", record.level(), record.args());
        }
    }

    fn flush(&self) {}
}

fn main() -> Result<(), SetLoggerError> {
    log::set_logger(&CONSOLE_LOGGER)?;
    log::set_max_level(LevelFilter::Info);

    info!("hello log");
    warn!("warning");
    error!("oops");
    Ok(())
}