How to get fmt::Display from a struct to display it in the fmt::Display of another struct?

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Im not sure how to name this question as I am new to Rust so feel free to suggest edits.

I have two structs. One is a Job struct, which contains a few numbers like how long a job takes, etc. The other is a JobSequence, which contains a Vec() of Jobs.

I implemented the fmt::Display trait for the Job so that it prints out its three number in this way:

(10, 12, 43)

Now, I would like to implement the fmt::Display trait for the JobSequence struct so that it iterates over each Job in the vector and displays them in this way:

(0, 10, 5)
(30, 10, 5)
(0, 10, 5)
(0, 10, 5)
(0, 10, 5)

I think(?) I should reuse the implemented trait of the Job struct and use it so that it simply, in a way, printouts them as a semi-list. This is my current implementation, but i have a feeling that is sloppy and there is a better way:

pub struct JobSequence {
    pub job_sequence: Vec<Job>,
}

impl fmt::Display for JobSequence {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        let mut final_output = String::new();
        for i in &self.job_sequence {
            final_output.push_str(i.to_string().as_str());
            final_output.push_str("\n");
        }
        write!(f, "{}", final_output)
    }
}
rust struct
1 Answers

You can re-use the the Display impl by passing it directly to write! with the {} format string:

impl fmt::Display for JobSequence {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        for i in &self.job_sequence {
            writeln!(f, "{}", i)?;
        }
        Ok(())
    }
}

You can read more about the different traits used by the formatting macros in the docs. (A plain {} uses std::fmt::Display.)

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