Cannot modify a struct field from implementation: “cannot borrow immutable borrowed content as mutable”

Question

I\'m trying to implement an iterator which will yield prime numbers. I store already found prime numbers in a Vec.

Here\'s my implementation:

Answer 1

Your PrimesIterator type contains a non-mutable reference to a Vec. You need to declare it as a mutable reference:

struct PrimesIterator<'a> {
    primes: &'a mut Vec,
    index: usize,
}

This will of course require you to also modify the iter() function to make sure it passes a mutable reference:

impl Primes {
    fn new() -> Primes {
        Primes { primes: vec!(2, 3) }
    }

    fn iter(&mut self) -> PrimesIterator {
        PrimesIterator { primes: &mut self.primes, index : 0 }
    }
}