faq.md

FAQ

• Why is it discouraged to accept a reference to a String (&String), Vec (&Vec), or Box (&Box) as a function argument?

  • To allow more generic code.

• What are the differences between String and str?

  • String is the dynamic heap string type, like Vec: use it when you need to own or modify your string data.
  • str is an immutable sequence of UTF-8 bytes of dynamic length somewhere in memory. Since the size is unknown, one can only handle it behind a pointer. This means that str most commonly2 appears as &str: a reference to some UTF-8 data, normally called a "string slice" or just a "slice".
  • Use String if you need owned string data (like passing strings to other threads, or building them at runtime), and use &str if you only need a view of a string.

• Why are explicit lifetimes needed in Rust?

  • The main reason is that while the compiler can see what your code does, it doesn't know what your intent was.

• What is the difference between iter and into_iter?

  • iter() iterates over the items by borrowing.
  • into_iter() iterates over the items, moving them into the new scope (takes ownership).
  • iter_mut() iterates over the items, giving a mutable reference to each item.