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use std::{
cell::RefCell,
rc::Rc,
};
pub struct ObservableValue<T>
where T: Clone
{
value: T,
subs: Vec<Subscription<T>>,
new_id: usize,
}
#[derive(Clone, Copy, Eq, PartialEq)]
pub struct SubscriptionId(usize);
struct Subscription<T> {
id: SubscriptionId,
callback: Box<dyn Fn(&T)>
}
impl<T> ObservableValue<T>
where T: Clone
{
pub fn new(initial_value: T) -> ObservableValue<T> {
ObservableValue {
value: initial_value,
new_id: 0,
subs: Vec::with_capacity(0),
}
}
pub fn get(&self) -> &T {
&self.value
}
pub fn set(&mut self, new_value: &T) {
self.value = new_value.clone();
self.call_subscribers();
}
fn call_subscribers(&self) {
for sub in self.subs.iter() {
(sub.callback)(&self.value)
}
}
pub fn connect<F>(&mut self, callback: F) -> SubscriptionId
where F: (Fn(&T)) + 'static
{
let id = SubscriptionId(self.new_id);
self.new_id = self.new_id.checked_add(1).expect("No overflow");
self.subs.push(Subscription {
id,
callback: Box::new(callback),
});
self.subs.shrink_to_fit();
id
}
pub fn disconnect(&mut self, sub_id: SubscriptionId) {
self.subs.retain(|sub| sub.id != sub_id);
self.subs.shrink_to_fit();
}
pub fn split(self) -> (ReadHalf<T>, WriteHalf<T>) {
let inner = Rc::new(RefCell::new(self));
(
ReadHalf {
inner: inner.clone(),
},
WriteHalf {
inner: inner
}
)
}
}
pub struct ReadHalf<T>
where T: Clone
{
inner: Rc<RefCell<ObservableValue<T>>>,
}
pub struct WriteHalf<T>
where T: Clone
{
inner: Rc<RefCell<ObservableValue<T>>>,
}
impl<T> ReadHalf<T>
where T: Clone
{
pub fn get(&self) -> T {
self.inner.borrow().get().clone()
}
pub fn connect<F>(&mut self, callback: F) -> SubscriptionId
where F: (Fn(&T)) + 'static
{
self.inner.borrow_mut().connect(callback)
}
pub fn disconnect(&mut self, sub_id: SubscriptionId) {
self.inner.borrow_mut().disconnect(sub_id)
}
}
impl<T> WriteHalf<T>
where T: Clone
{
pub fn set(&mut self, new_value: &T) {
self.inner.borrow_mut().set(new_value)
}
}
#[cfg(test)]
mod test {
use std::{
cell::Cell,
rc::Rc,
};
use super::ObservableValue;
#[test]
fn new_get_set() {
let mut ov = ObservableValue::new(17);
assert_eq!(*ov.get(), 17);
ov.set(&18);
assert_eq!(*ov.get(), 18);
}
#[test]
fn connect_set() {
let mut ov = ObservableValue::<u32>::new(17);
let mirror: Rc<Cell<u32>> = Rc::new(Cell::new(0));
let mc = mirror.clone();
ov.connect(move |val| {
mc.set(*val);
});
assert_eq!(mirror.get(), 0);
ov.set(&18);
assert_eq!(mirror.get(), 18);
}
#[test]
fn disconnect() {
let mut ov = ObservableValue::<u32>::new(17);
let mirror_1: Rc<Cell<u32>> = Rc::new(Cell::new(0));
let mirror_2: Rc<Cell<u32>> = Rc::new(Cell::new(0));
let mc1 = mirror_1.clone();
let sub_id_1 = ov.connect(move |val| {
mc1.set(*val);
});
let mc2 = mirror_2.clone();
let _sub_id_2 = ov.connect(move |val| {
mc2.set(*val);
});
ov.set(&18);
assert_eq!(mirror_1.get(), 18);
assert_eq!(mirror_2.get(), 18);
ov.disconnect(sub_id_1);
ov.set(&19);
assert_eq!(mirror_1.get(), 18);
assert_eq!(mirror_2.get(), 19);
}
#[test]
fn split() {
let ov = ObservableValue::<u32>::new(17);
let (mut r, mut w) = ov.split();
let mirror: Rc<Cell<u32>> = Rc::new(Cell::new(0));
let mc = mirror.clone();
r.connect(move |val| {
mc.set(*val);
});
assert_eq!(mirror.get(), 0);
w.set(&18);
assert_eq!(mirror.get(), 18);
}
}