comparable to asynchronous systems, but they do not actually make things asynchronous). Asynchronous operations in Tornado generally return placeholder objects (Futures), with the exception of some low- level get_current_user() may not, so the latter form is necessary if loading the user requires asynchronous operations. The user object may be any type of the application’s choosing. RequestHandler.detach() → IOStream response to a ping frame is received. exception tornado.websocket.WebSocketClosedError Raised by operations on a closed connection. Added in version 3.2. Client-side support tornado.websocket.websocket_connect(url:

comparable to asynchronous systems, but they do not actually make things asynchronous). Asynchronous operations in Tornado generally return placeholder objects (Futures), with the exception of some low-level get_current_user() may not, so the latter form is necessary if loading the user requires asynchronous operations. The user object may be any type of the application’s choosing. RequestHandler.detach() → IOStream response to a ping frame is received. exception tornado.websocket.WebSocketClosedError Raised by operations on a closed connection. Added in version 3.2. Client-side support tornado.websocket.websocket_connect(url:

height: 12 }, ]; let mut sort_operations = vec![]; let value = String::from("closure called"); list.sort_by_key(|r| { sort_operations.push(value); r.width }); value（一个 String）插入 sort_operations vector 来实现计数。闭包捕获了 value，然后通过将 value 的所有权转移给 sort_operations vector 的方式将其移出闭包。这个闭包只能被调用一次；尝试第二次调用它将无法工作，因为 这时 value 已经不在闭包的环境中，无法被再次插入 sort_operations 中！因而，这个闭包只 实现了 FnOn sort_by_key(|r| { | --- captured by this `FnMut` closure 18 | sort_operations.push(value); | ^^^^^ move occurs because `value` has type `String`