From 3184f27c004ce49fffa118f293d263bb09723cce Mon Sep 17 00:00:00 2001
From: Matt Hunzinger <matthunz2@gmail.com>
Date: Sun, 18 Feb 2024 08:55:30 -0500
Subject: [PATCH] Add task::from_fn

---
 src/task/from_fn.rs | 39 +++++++++++++++++++++++++++++++++++++++
 src/task/mod.rs     |  9 +++++++++
 2 files changed, 48 insertions(+)
 create mode 100644 src/task/from_fn.rs

diff --git a/src/task/from_fn.rs b/src/task/from_fn.rs
new file mode 100644
index 0000000..3afed9f
--- /dev/null
+++ b/src/task/from_fn.rs
@@ -0,0 +1,39 @@
+use super::Task;
+use std::marker::PhantomData;
+
+pub fn from_fn<F, M, O>(f: F) -> FromFn<F, M>
+where
+    F: FnMut(&mut M) -> O,
+{
+    FromFn {
+        f,
+        _marker: PhantomData,
+    }
+}
+
+pub struct FromFn<F, M> {
+    f: F,
+    _marker: PhantomData<M>,
+}
+
+impl<F, M, O> Task<M> for FromFn<F, M>
+where
+    F: FnMut(&mut M) -> O,
+{
+    type Output = O;
+
+    type State = ();
+
+    fn build(&mut self, _cx: &super::Context<M, ()>, model: &mut M) -> (Self::Output, Self::State) {
+        ((self.f)(model), ())
+    }
+
+    fn rebuild(
+        &mut self,
+        _cx: &super::Context<M, ()>,
+        model: &mut M,
+        _state: &mut Self::State,
+    ) -> Self::Output {
+        (self.f)(model)
+    }
+}
diff --git a/src/task/mod.rs b/src/task/mod.rs
index a445957..9810c98 100644
--- a/src/task/mod.rs
+++ b/src/task/mod.rs
@@ -1,5 +1,8 @@
 use std::rc::Rc;
 
+mod from_fn;
+pub use self::from_fn::{from_fn, FromFn};
+
 mod then;
 pub use self::then::Then;
 
@@ -7,6 +10,12 @@ pub struct Context<M, A> {
     waker: Rc<dyn Fn(Rc<dyn Fn(&mut M) -> Option<A>>)>,
 }
 
+impl<M, A> Context<M, A> {
+    pub fn update(&self, f: impl Fn(&mut M) -> Option<A> + 'static) {
+        (self.waker)(Rc::new(f))
+    }
+}
+
 pub trait Task<M, A = ()> {
     type Output;