add vh section

content/docs/application.md

@@ -72,3 +72,36 @@ Combining multiple applications with different state is possible as well.
 This limitation can easily be overcome with the [App::boxed](https://docs.rs/actix-web/*/actix_web/struct.App.html#method.boxed) method, which converts an App into a boxed trait object.
 
 {{< include-example example="application" file="state.rs" section="combine" >}}
+
+## Using an Application Prefix to Compose Applications
+
+The `App::prefix()` method allows to set a specific application prefix.
+This prefix represents a resource prefix that will be prepended to all resource patterns added
+by the resource configuration. This can be used to help mount a set of routes at a different
+location than the included callable's author intended while still maintaining the same
+resource names.
+
+For example:
+
+{{< include-example example="url-dispatch" file="prefix.rs" section="prefix" >}}
+
+In the above example, the *show_users* route will have an effective route pattern of
+*/users/show* instead of */show* because the application's prefix argument will be prepended
+to the pattern. The route will then only match if the URL path is */users/show*,
+and when the `HttpRequest.url_for()` function is called with the route name show_users,
+it will generate a URL with that same path.
+
+## Application predicates and virtual hosting
+
+You can think of a predicate as a simple function that accepts a *request* object reference
+and returns *true* or *false*. Formally, a predicate is any object that implements the
+[`Predicate`](../actix_web/pred/trait.Predicate.html) trait. Actix provides
+several predicates, you can check
+[functions section](../../actix-web/actix_web/pred/index.html#functions) of api docs.
+
+Any of this predicates could be used 
+with [`App::filter()`](../actix_web/struct.App.html#method.filter) method. One of the
+provided predicates is [`Host`](../actix_web/pred/fn.Host.html), it can be used
+as application's filter based on request's host information.
+
+{{< include-example example="application" file="vh.rs" section="vh" >}}

examples/application/src/main.rs

@@ -3,6 +3,7 @@ extern crate actix_web;
 use actix_web::{http::Method, server, App, HttpRequest, HttpResponse, Responder};
 
 mod state;
+mod vh;
 
 fn make_app() {
 // <make_app>

examples/application/src/vh.rs

@@ -0,0 +1,23 @@
+#![allow(unused)]
+extern crate actix_web;
+use actix_web::{http::Method, server, App, HttpRequest, HttpResponse, Responder};
+
+mod state;
+
+// <vh>
+fn main() {
+    let server = server::new(|| {
+        vec![
+            App::new()
+                .filter(pred::Host("www.rust-lang.org"))
+                .resource("/", |r| r.f(|r| HttpResponse::Ok())),
+            App::new()
+                .filter(pred::Host("users.rust-lang.org"))
+                .resource("/", |r| r.f(|r| HttpResponse::Ok())),
+            App::new().resource("/", |r| r.f(|r| HttpResponse::Ok())),
+        ]
+    });
+
+    server.run();
+}
+// </vh>