rustlings/exercises/quiz2.rs

// quiz2.rs
//
// This is a quiz for the following sections:
// - Strings
// - Vecs
// - Move semantics
// - Modules
// - Enums
//
// Let's build a little machine in the form of a function. As input, we're going
// to give a list of strings and commands. These commands determine what action
// is going to be applied to the string. It can either be:
// - Uppercase the string
// - Trim the string
// - Append "bar" to the string a specified amount of times
// The exact form of this will be:
// - The input is going to be a Vector of a 2-length tuple,
//   the first element is the string, the second one is the command.
// - The output element is going to be a Vector of strings.
//
// No hints this time!


#[derive(Debug,PartialEq)]
pub enum Command {
    Uppercase,
    Trim,
    Append(usize),
}

mod my_module {
    use super::Command;

    // TODO: Complete the function signature!
    pub fn transformer(input: Vec<(String,Command)>)-> Vec<String> {
        // TODO: Complete the output declaration!
        let mut output:Vec<String> = vec![];
        for (string, command) in input.iter() {
            // TODO: Complete the function body. You can do it!
            match command{
                Command::Uppercase=>{
                    output.push(string.to_uppercase())
                }
                Command::Trim=>{
                    output.push(string.trim().to_string())
                }
                Command::Append(size)=>{
                    // let mut ap = string.clone();
                    // for _ in 0..*size {
                    //     ap.push_str("bar");
                    // }
                    // output.push(ap);
                
                    let repeated_bar: String = if *size == 1 {
                        String::from("bar")
                    } else {
                        //这里如果是这样写的话，需要排除1，否则无法正确凭借，只有当重复时候可以使用repeat
                        std::iter::repeat("bar").take(*size).collect()
                    };
                    let result = string.clone() + &repeated_bar;
                    output.push(result);
                }
            }
        }
        output
    }
}

#[cfg(test)]
mod tests {
    // TODO: What do we need to import to have `transformer` in scope?
    use super::my_module::transformer;
    use super::Command;

    #[test]
    fn it_works() {
        let output = transformer(vec![
            ("hello".into(), Command::Uppercase),
            (" all roads lead to rome! ".into(), Command::Trim),
            ("foo".into(), Command::Append(1)),
            ("bar".into(), Command::Append(5)),
        ]);
        assert_eq!(output[0], "HELLO");
        assert_eq!(output[1], "all roads lead to rome!");
        assert_eq!(output[2], "foobar");
        assert_eq!(output[3], "barbarbarbarbarbar");
    }
}