如何在Rust中将字符连接到字符串？

fn main() {
    let mut s = String::new();
    s.push('a');
    s.push('b');
    s.push('c');
    println!("{}", s); // 输出: abc
}

fn main() {
    let mut s = String::new();
    let chars = ['a', 'b', 'c'];
    s.push_str(&chars.iter().map(|&c| c.to_string()).collect::<String>());
    println!("{}", s); // 输出: abc
}

fn main() {
    let s = format!("{}{}{}", 'a', 'b', 'c');
    println!("{}", s); // 输出: abc
}

fn main() {
    let chars = ['a', 'b', 'c'];
    let s: String = chars.iter().map(|&c| c.to_string()).collect();
    println!("{}", s); // 输出: abc
}

fn main() {
    let s = "abc";
    let mut string = s.to_string();
    string.push('d');
    println!("{}", string); // 输出: abcd
}