14.2.3. 筛选匹配断言的 CSV 记录

仅仅 返回 data 中字段（field）与 query 匹配的的行。

use error_chain::error_chain;

use std::io;

error_chain!{
    foreign_links {
        Io(std::io::Error);
        CsvError(csv::Error);
    }
}

fn main() -> Result<()> {
    let query = "CA";
    let data = "\
City,State,Population,Latitude,Longitude
Kenai,AK,7610,60.5544444,-151.2583333
Oakman,AL,,33.7133333,-87.3886111
Sandfort,AL,,32.3380556,-85.2233333
West Hollywood,CA,37031,34.0900000,-118.3608333";

    let mut rdr = csv::ReaderBuilder::new().from_reader(data.as_bytes());
    let mut wtr = csv::Writer::from_writer(io::stdout());

    wtr.write_record(rdr.headers()?)?;

    for result in rdr.records() {
        let record = result?;
        if record.iter().any(|field| field == query) {
            wtr.write_record(&record)?;
        }
    }

    wtr.flush()?;
    Ok(())
}

免责声明：此实例改编自csv crate 教程。