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53 lines
1.6 KiB
Rust
53 lines
1.6 KiB
Rust
// refcell1.rs
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//
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// Interior mutability is a design pattern in Rust that allows you to mutate
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// data even when there are immutable references to that data;
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// normally, this action is disallowed by the borrowing rules.
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// The RefCell<T> type represents single ownership over the data it holds.
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// Recall the borrowing rules in Rust:
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// 1. At any given time, you can have either (but not both) one mutable
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// reference or any number of immutable references.
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// 2. References must always be valid.
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// With references and Box<T>, the borrowing rules’ invariants are enforced at
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// compile time. With RefCell<T>, these invariants are enforced at runtime.
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// With references, if you break these rules, you’ll get a compiler error.
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// With RefCell<T>, if you break these rules, your program will panic and exit.
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// The RefCell<T> type is useful when you’re sure your code follows the
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// borrowing rules but the compiler is unable to understand and guarantee that.
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// I AM NOT DONE
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use std::cell::RefCell;
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#[derive(Debug)]
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#[allow(dead_code)]
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struct User {
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name: RefCell<String>,
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}
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#[allow(dead_code)]
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impl User {
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fn name(&self) -> String {
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self.name.borrow().to_string()
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}
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// Note: do not use &mut self!
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fn set_name(&self, name: String) {
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todo!()
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}
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}
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fn main() {
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let u = User {
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name: RefCell::new("Alice".to_string()),
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};
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println!("My name is {}!", *u.name.borrow());
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let new_name = "Bob".to_string();
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u.set_name(new_name.clone());
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println!("My name is {}!", *u.name.borrow());
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}
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