Iterator::find

Iterator::find is a function which when passed an iterator, will return
the first element which satisfies the predicate as an Option. Its
signature:

  1. pub trait Iterator {
  2.     // The type being iterated over.
  3.     type Item;
  5.     // `find` takes `&mut self` meaning the caller may be borrowed
  6.     // and modified, but not consumed.
  7.     fn find<P>(&mut self, predicate: P) -> Option<Self::Item> where
  8.         // `FnMut` meaning any captured variable may at most be
  9.         // modified, not consumed. `&Self::Item` states it takes
  10.         // arguments to the closure by reference.
  11.         P: FnMut(&Self::Item) -> bool {}
  12. }
  1. fn main() {
  2.     let vec1 = vec![1, 2, 3];
  3.     let vec2 = vec![4, 5, 6];
  5.     // `iter()` for vecs yields `&i32`.
  6.     let mut iter = vec1.iter();
  7.     // `into_iter()` for vecs yields `i32`.
  8.     let mut into_iter = vec2.into_iter();
  10.     // A reference to what is yielded is `&&i32`. Destructure to `i32`.
  11.     println!("Find 2 in vec1: {:?}", iter     .find(|&&x| x == 2));
  12.     // A reference to what is yielded is `&i32`. Destructure to `i32`.
  13.     println!("Find 2 in vec2: {:?}", into_iter.find(| &x| x == 2));
  15.     let array1 = [1, 2, 3];
  16.     let array2 = [4, 5, 6];
  18.     // `iter()` for arrays yields `&i32`
  19.     println!("Find 2 in array1: {:?}", array1.iter()     .find(|&&x| x == 2));
  20.     // `into_iter()` for arrays unusually yields `&i32`
  21.     println!("Find 2 in array2: {:?}", array2.into_iter().find(|&&x| x == 2));
  22. }

See also:

std::iter::Iterator::find