CODEWITHSUNDEEP
rustborrow-checker
tkachuko
tkachuko

Reputation: 1986

Move of struct instance in closure and in iteration

I recently started to learn rust using simple exercises with structs. In this particular case I would like to iterate over a collection field in a struct. However I keep getting compilation errors because reference to a struct cannot be used in a filter method as well as in a loop:

#[derive(Debug, PartialEq)]
pub struct CustomSet<T> {
    buckets: Vec<LinkedList<T>>,
    size: usize,
}

impl<T> CustomSet<T> where T: Eq + Clone + Hashable {
  pub fn new(input: &[T]) -> Self -> {...} // implemented
  pub fn contains(self, element: &T) -> bool {...} //implemented
  pub fn add(&mut self, element: T) {...} // implemented
  pub fn is_subset(&self, other: &Self) -> bool {
    for bucket in &self.buckets {
      for el in bucket {
        // error: cannot move out of `*other` which is behind a shared reference
        if !other.contains(&el) {
          return false;
        }
      }
    }
    return true;
  }
  pub fn intersection(&self, other: &Self) -> Self {
    let mut result = CustomSet::new(&[]);
    self.buckets.iter().for_each(|bucket|
      bucket.iter()
        // Cannot move out of `*other`, as `other` is a captured variable in an `FnMut` closure
        .filter(|el| other.contains(el))
        .for_each(|el| result.add(el.clone()))
      );
    result
  }
}

I guess my two misunderstandings are:

Thanks in advance for any help in understanding this behavior and your suggestions how to fix it.

Upvotes: 0

Views: 132

Answers (1)

tkachuko
tkachuko

Reputation: 1986

As suggested by Silvio in the comment the issue is in contains method that borrows the object. Changing the method to use the reference made it all work.

Upvotes: 0

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