Iterator

TL;DR

  • Use .iter() when you only need to look at elements.
  • Use .iter_mut() when you want to modify elements in place.
  • Use .into_iter() when you need ownership and want to consume or move elements.

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#Summary

Method Returns Ownership Typical Use Case
.iter() &T Borrow only read elements
.iter_mut() &mut T Mutable borrow modify elements in place
.into_iter() T Ownership consume/move elements

#Example 

pub fn transformer(input: Vec<(String, Command)>) -> Vec<String> {
	input.into_iter().map(|(s, c)| match c {
		Command::Uppercase => s.to_uppercase(),
		Command::Trim => s.trim().to_string(),
		Command::Append(amount) => s + &"bar".repeat(amount),
	}) .collect()
}

#.map(|(s, c)| match c { ... })

  • Applies a function to each element.
  • Destructures the tuple (s, c) into the string s and the command c.
  • Depending on the command, produces a new String:
    • Uppercase → converts the string to uppercase.
    • Trim → removes leading and trailing whitespace.
    • Append(amount) → appends “bar” amount times.

#.collect()

  • Collects the results of the iterator.
  • Builds a new vector: Vec<String>.

#.iter_iter()

  • Creates a consuming iterator.
  • The original vector gives up its elements → we now own the Strings.
  • Important because s + “bar” consumes the string (ownership).
  • After calling this, the original vector can no longer be used.

#Trait Iterator

Implementing iterators with Trait Iterator.