A macro to ease the concatination of meny optional string fields like in large structs representing json objects that have many possibly empty fields

rust_easier_optional_string_field_concat.rs

use std::fmt;


macro_rules! txt_concat {
    ($($model: expr), *) => {{
        let mut s = String::new();
        $(
            if let Some(t) = $model {
                s.push_str(&t);
                s.push(' ');
            }
        )*

        s
    }};
}

struct Invoice {
    supplier_name: Option<String>,
    supplier_id: Option<String>,
    department: Option<String>,
    text: Option<String>,
}

impl Invoice {
    fn new(s_name: &str, s_id: &str, dept: &str, text: &str) -> Self {
        Invoice {
            supplier_name: Some(s_name.to_string()),
            supplier_id: Some(s_id.to_string()),
            department: Some(dept.to_string()),
            text: Some(text.to_string()),
        }
    }
}

impl fmt::Display for Invoice {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        let text = txt_concat!(
            &self.supplier_name,
            &self.supplier_id,
            &self.department,
            &self.text
            );
        write!(f, "{}", text)
    }
}