所以我有这样一个问题:
struct User {
reference: String,
email: String,
firstname: String,
lastname: String
}
fn main() {
let user = User {
reference: "ref".to_string(),
email: "em@ail.com".to_string(),
firstname: "John".to_string(),
lastname: "Doe".to_string()
};
concat!(&user.firstname.as_string(), " ", &user.lastname.as_string());
}
这里返回了一个错误:
error: expected a literal
concat!(&user.firstname.as_string(), " ", &user.lastname.as_string());
^~~~~~~~~~~~~~~~~~~~~~~~~~
但是我认为.as_string()
已经使其成为文字了,不是吗?我还发现到处都有as_slice()
和as_str()
的引用,这很令人困惑。到底哪一个是正确的?
更新好的,我希望不必在这里粘贴整个内容,但我似乎必须这样做:
extern crate postgres;
use postgres::{Connection, SslMode};
struct User {
reference: String,
email: String,
firstname: String,
lastname: String
}
fn main() {
let conn = Connection::connect("postgres://postgres:postgres@localhost/mydb", &SslMode::None).unwrap();
let user = User {
reference: "ref".to_string(),
email: "em@ail.com".to_string(),
firstname: "John".to_string(),
lastname: "Doe".to_string()
};
let query = "INSERT INTO foo (user_id, name) VALUES ((SELECT id FROM user WHERE email = $1), $2)";
conn.execute(query, &[&user.email, concat!(&user.firstname.as_slice(), " ", &user.lastname.as_slice())]).unwrap();
}