pub struct FamilyIterator<'a> {
    offset: usize,
    family: &'a Family,
}

impl<'a> Iterator for FamilyIterator<'a> {
    type Item = &'a Person;

    fn next(&mut self) -> Option<&'a Person> {
        let result = match self.offset {
            0 => &self.family.a,
            1 => &self.family.b,
            2 => &self.family.c,
            _ => return None,
        };
        self.offset += 1;
        Some(&result)
    }
}

impl<'a> IntoIterator for &'a Family {
    type Item = &'a Person;
    type IntoIter = FamilyIterator<'a>;

    fn into_iter(self) -> Self::IntoIter {
        FamilyIterator {
            offset: 0,
            family: self,
        }
    }
}

#[derive(Debug)]
pub struct Person {
    age: usize,
}

#[derive(Debug)]
pub struct Family {
    a: Person,
    b: Person,
    c: Person,
}

fn main() {
    let family = Family {
        a: Person { age: 1 },
        b: Person { age: 2 },
        c: Person { age: 3 },
    };
    println!("Current family: {:?}", family);
    /*
    for person in &family {
        println!("Person's age: {:?}", person.age);
        person.age += 1
    }*/
    println!("Updated family: {:?}", family);
}