X-Git-Url: https://git.ralfj.de/rust-101.git/blobdiff_plain/2d40516a8393db1f27bb822ff95c71a1a9c82537..ab7f9b241429bd675b437d2437799de75d2f409b:/workspace/src/part12.rs

diff --git a/workspace/src/part12.rs b/workspace/src/part12.rs
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-// Rust-101, Part 12: Rc, Interior Mutability, Cell, RefCell
-// =========================================================
-
-use std::rc::Rc;
-use std::cell::{Cell, RefCell};
-
-
-
-#[derive(Clone)]
-struct Callbacks {
-    callbacks: Vec<Rc<Fn(i32)>>,
-}
-
-impl Callbacks {
-    pub fn new() -> Self {
-        Callbacks { callbacks: Vec::new() }
-    }
-
-    // Registration works just like last time, except that we are creating an `Rc` now.
-    pub fn register<F: Fn(i32)+'static>(&mut self, callback: F) {
-        unimplemented!()
-    }
-
-    pub fn call(&self, val: i32) {
-        // We only need a shared iterator here. Since `Rc` is a smart pointer, we can directly call the callback.
-        for callback in self.callbacks.iter() {
-            unimplemented!()
-        }
-    }
-}
-
-// Time for a demo!
-fn demo(c: &mut Callbacks) {
-    c.register(|val| println!("Callback 1: {}", val));
-    c.call(0); c.clone().call(1);
-}
-
-pub fn main() {
-    let mut c = Callbacks::new();
-    demo(&mut c);
-}
-
-// ## Interior Mutability
-
-// So, let us put our counter in a `Cell`, and replicate the example from the previous part.
-fn demo_cell(c: &mut Callbacks) {
-    {
-        let count = Cell::new(0);
-        // Again, we have to move ownership of the `count` into the environment closure.
-        c.register(move |val| {
-            // In here, all we have is a shared reference of our environment. But that's good enough for the `get` and `set` of the cell!
-            let new_count = count.get()+1;
-            count.set(new_count);
-            println!("Callback 2: {} ({}. time)", val, new_count);
-        } );
-    }
-
-    c.call(2); c.clone().call(3);
-}
-
-
-// ## `RefCell`
-
-// Our final version of `Callbacks` puts the closure environment into a `RefCell`.
-#[derive(Clone)]
-struct CallbacksMut {
-    callbacks: Vec<Rc<RefCell<FnMut(i32)>>>,
-}
-
-impl CallbacksMut {
-    pub fn new() -> Self {
-        CallbacksMut { callbacks: Vec::new() }
-    }
-
-    pub fn register<F: FnMut(i32)+'static>(&mut self, callback: F) {
-        unimplemented!()
-    }
-
-    pub fn call(&mut self, val: i32) {
-        for callback in self.callbacks.iter() {
-            // We have to *explicitly* borrow the contents of a `RefCell` by calling `borrow` or `borrow_mut`.
-            let mut closure = callback.borrow_mut();
-            // Unfortunately, Rust's auto-dereference of pointers is not clever enough here. We thus have to explicitly
-            // dereference the smart pointer and obtain a mutable reference to the content.
-            (&mut *closure)(val);
-        }
-    }
-}
-
-// Now we can repeat the demo from the previous part - but this time, our `CallbacksMut` type
-// can be cloned.
-fn demo_mut(c: &mut CallbacksMut) {
-    c.register(|val| println!("Callback 1: {}", val));
-    c.call(0);
-
-    {
-        let mut count: usize = 0;
-        c.register(move |val| {
-            count = count+1;
-            println!("Callback 2: {} ({}. time)", val, count);
-        } );
-    }
-    c.call(1); c.clone().call(2);
-}
-
-// **Exercise 12.1**: Write some piece of code using only the available, public interface of `CallbacksMut` such that a reentrant call to a closure
-// is happening, and the program panics because the `RefCell` refuses to hand out a second mutable borrow of the closure's environment.
-