Use futures-preview instead of futures

web/Cargo.toml

@@ -17,7 +17,7 @@ maintenance = { status = "actively-developed" }
 [dependencies]
 iced = { version = "0.1.0-alpha", path = ".." }
 dodrio = "0.1.0"
-futures = "0.1"
+futures-preview = "=0.3.0-alpha.18"
 wasm-bindgen = "0.2.50"
 
 [dependencies.web-sys]

web/examples/tour/Cargo.toml

@@ -11,7 +11,7 @@ crate-type = ["cdylib"]
 [dependencies]
 iced_web = { path = "../.." }
 wasm-bindgen = "0.2.50"
-futures = "0.1"
+futures-preview = "=0.3.0-alpha.18"
 log = "0.4"
 console_error_panic_hook = "0.1.6"
 console_log = "0.1.2"

web/examples/tour/src/lib.rs

@@ -1,4 +1,4 @@
-use futures::{future, Future};
+use futures::Future;
 use iced_web::UserInterface;
 use wasm_bindgen::prelude::*;
 
@@ -23,10 +23,10 @@ impl iced_web::UserInterface for Tour {
     fn update(
         &mut self,
         message: tour::Message,
-    ) -> Box<dyn Future<Item = tour::Message, Error = ()>> {
+    ) -> Option<Box<dyn Future<Output = tour::Message>>> {
         self.update(message);
 
-        Box::new(future::err(()))
+        None
     }
 
     fn view(&mut self) -> iced_web::Element<tour::Message> {

web/src/lib.rs

@@ -19,7 +19,7 @@ pub trait UserInterface {
     fn update(
         &mut self,
         message: Self::Message,
-    ) -> Box<dyn Future<Item = Self::Message, Error = ()>>;
+    ) -> Option<Box<dyn Future<Output = Self::Message>>>;
 
     fn view(&mut self) -> Element<Self::Message>;