Listing

Print tasks with a for loop.

Listing

Printing the tasks only needs reading, so &self is enough. We loop over the vector by borrowing it with &self.gorevler:

fn listele(&self) {
    for g in &self.gorevler {
        let isaret = if g.bitti { "x" } else { " " };
        println!("[{}] {}: {}", isaret, g.id, g.metin);
    }
}

Had we written for g in self.gorevler, we would try to move the vector; since a field behind &self can't be moved, we'd get a compile error.

Empty list message

A descriptive message for an empty list is a good user experience:

fn listele(&self) {
    if self.gorevler.is_empty() {
        println!("Görev yok.");
        return;
    }
    for g in &self.gorevler {
        // ...
    }
}

An early return keeps the main logic unindented.

Exercise List the tasks

Write the methods ekle and listele for Liste. Add "Süt al" and "Kod yaz" and call listele().

Show example solution

struct Gorev {
    id: u32,
    metin: String,
    bitti: bool,
}

struct Liste {
    gorevler: Vec<Gorev>,
    sonraki_id: u32,
}

impl Liste {
    fn ekle(&mut self, metin: &str) -> u32 {
        self.sonraki_id += 1;
        self.gorevler.push(Gorev {
            id: self.sonraki_id,
            metin: metin.to_string(),
            bitti: false,
        });
        self.sonraki_id
    }
    fn listele(&self) {
        for g in &self.gorevler {
            let isaret = if g.bitti { "x" } else { " " };
            println!("[{}] {}: {}", isaret, g.id, g.metin);
        }
    }
}

fn main() {
    let mut liste = Liste {
        gorevler: Vec::new(),
        sonraki_id: 0,
    };
    liste.ekle("Süt al");
    liste.ekle("Kod yaz");
    liste.listele();
}

Test yourself

What does <code>listele</code> print if the list is empty?
- Nothing; the loop never runs
- It panics
- It prints "[]"
- It prints None
Show answer

Nothing; the loop never runs — A for loop over an empty vector runs zero times. To be user-friendly, a separate message can be shown with is_empty.

Loop by borrowing

for g in ____self.gorevler {
    println!("{}", g.metin);
}

Show answer

for g in &self.gorevler {
    println!("{}", g.metin);
}

Loop and result

for g in &v

Borrows
for g in &mut v

Loops while modifying
for g in v

Moves
v.is_empty()

Is it empty?

Next lesson: Marking done

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