Implement future-based `Command` in `iced_core`

3 files changed, 60 insertions, 0 deletions

diff --git a/core/Cargo.toml b/core/Cargo.toml
index a244bcba..f2492345 100644
--- a/core/Cargo.toml
+++ b/core/Cargo.toml
@@ -6,3 +6,10 @@ edition = "2018"
 description = "The essential concepts of Iced"
 license = "MIT"
 repository = "https://github.com/hecrj/iced"
+
+[features]
+# Exposes a future-based `Command` type
+command = ["futures"]
+
+[dependencies]
+futures = { version = "0.3", optional = true }
diff --git a/core/src/command.rs b/core/src/command.rs
new file mode 100644
index 00000000..ae901bd8
--- /dev/null
+++ b/core/src/command.rs
@@ -0,0 +1,49 @@
+use futures::future::{BoxFuture, Future, FutureExt};
+
+pub struct Command<T> {
+    futures: Vec<BoxFuture<'static, T>>,
+}
+
+impl<T> Command<T> {
+    pub fn none() -> Self {
+        Self {
+            futures: Vec::new(),
+        }
+    }
+
+    pub fn attempt<A>(
+        future: impl Future<Output = T> + 'static + Send,
+        f: impl Fn(T) -> A + 'static + Send,
+    ) -> Command<A> {
+        Command {
+            futures: vec![future.map(f).boxed()],
+        }
+    }
+
+    pub fn batch(commands: impl Iterator<Item = Command<T>>) -> Self {
+        Self {
+            futures: commands.flat_map(|command| command.futures).collect(),
+        }
+    }
+
+    pub fn futures(self) -> Vec<BoxFuture<'static, T>> {
+        self.futures
+    }
+}
+
+impl<T, A> From<A> for Command<T>
+where
+    A: Future<Output = T> + 'static + Send,
+{
+    fn from(future: A) -> Self {
+        Self {
+            futures: vec![future.boxed()],
+        }
+    }
+}
+
+impl<T> std::fmt::Debug for Command<T> {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        f.debug_struct("Command").finish()
+    }
+}
diff --git a/core/src/lib.rs b/core/src/lib.rs
index b61f2eae..3816f8a2 100644
--- a/core/src/lib.rs
+++ b/core/src/lib.rs
@@ -3,6 +3,8 @@ pub mod widget;
 mod align;
 mod background;
 mod color;
+#[cfg(feature = "command")]
+mod command;
 mod font;
 mod length;
 mod point;
@@ -12,6 +14,8 @@ mod vector;
 pub use align::Align;
 pub use background::Background;
 pub use color::Color;
+#[cfg(feature = "command")]
+pub use command::Command;
 pub use font::Font;
 pub use length::Length;
 pub use point::Point;