Index

Rust

  1. Guessing Game
  2. Common Programming Concepts
    1. Variables and Mutability
    2. Data Types
    3. Function
    4. Control Flow
  3. Understanding Ownership
    1. References and Borrowing
    2. The Slice Type
  4. Using Structs
    1. An Example Program Using Structs
    2. Method Syntax
  5. Enums and Pattern Matching
    1. The match Control Flow Operator
    2. Concise Control Flow with if let
  6. Managing Growing Projects with Packages, Crates, and Modules
    1. Defining Modules to Control Scope and Privacy
    2. Paths for Referring to an Item in the Module Tree
    3. Bringing Paths into Scope with the use Keyword
    4. Separating Modules into Different Files
  7. Common Collections
    1. Storing UTF-8 Encoded Text with Strings
    2. Storing Keys with Associated Values in Hash Maps
  8. Error Handling
    1. Unrecoverable Errors with panic!
    2. Recoverable Errors with Result
  9. Generic Types, Traits, and Lifetimes
    1. Traits: Defining Shared Behavior
    2. Generics Rust by Example
      1. Functions
      2. Implementation
  10. Writing Automated Tests
  11. Object Oriented Programming
  12. Adding dependancies
  13. Option Take
  14. RefCell
  15. mem
  16. Data Structure
    1. Linked List
    2. Binary search tree
    3. N-ary Sum tree
  17. Recipe
    1. Semi colon
    2. Calling rust from python
    3. Default
    4. Crytocurrency With rust
    5. Function chaining
    6. Question Mark Operator
    7. Tests with println
    8. lib and bin
    9. Append vector to hash map
    10. Random Number
    11. uuid4
    12. uwrap and option
  18. Blockchain with Rust
  19. Near Protocol
    1. Startup code
    2. Couter
    3. Status
    4. Avrit
  20. Actix-web

RefCell


RefCell



https://doc.rust-lang.org/std/cell/struct.RefCell.html

A mutable memory location with dynamically checked borrow rules

pub fn borrow(&self) -> Ref<T>
Immutably borrows the wrapped value.

fn main() {
    use std::cell::RefCell;

    let c = RefCell::new(5);
    
    let borrowed_five = c.borrow();
    let borrowed_five2 = c.borrow();
    println!("{}", borrowed_five); // 5
    println!("{}", borrowed_five2); // 5

}



pub fn borrow_mut(&self) -> RefMut<T>

Mutably borrows the wrapped value.

use std::cell::RefCell;

let c = RefCell::new(5);

*c.borrow_mut() = 7;

assert_eq!(*c.borrow(), 7);


Error code:
fn main() {
    use std::cell::RefCell;

    let c = RefCell::new(5);
    
    c.borrow_mut() = 7;
}

images/949-1.png



Another example
fn main() {
    use std::cell::RefCell;

    #[derive(Clone)]
    struct Node {
        next: String,
    }

    let c = RefCell::new(Node {
        next: "hello".to_owned(),
    });
    c.borrow_mut().next = "bye".to_owned();

    println!("{:?}", c.borrow().next); // "bye"
}