ifletx=Some(2){dbg!(x);} 其实if let还可以接else分支的,我们再来看个例子 fnmain(){letfavorite_color:Option<&str>=None;letis_tuesday=false;letage:Result<u8,_>="34".parse();ifletSome(color)=favorite_color{println!("Using your favorite color, {color}, as the background");}elseifis...
fn use_data(data: &Vec<i32>) { // do something } fn main() { let data = vec![1, 2, 3]; use_data(&data); // Correct use_data(data); // Incorrect } 保持对参数的引用和传递一致。 在match表达式内使用=而不是if来匹配守卫: let num = 10; match num { x if x = 5 => prin...
fn use_data(data: &Vec<i32>) { // do something } fn main() { let data = vec![1, 2, 3]; use_data(&data); // Correct use_data(data); // Incorrect } 保持对参数的引用和传递一致。 在match表达式内使用=而不是if来匹配守卫 let num = 10; match num { x if x = 5 => pr...
{ user_msg = stream.next() => { let user_msg = match user_msg { Some(msg) => b!(msg), None => break Ok(()), }; if user_msg.starts_with("/help") { b!(sink.send(HELP_MSG).await); } else if user_msg.starts_with("/name") { // ... if changed_name { b!...
If we had a way to quantify over places, we could incorporate those places into a single type to give the step parameter. For example (wildly inventing syntax): for<place waker,placecontext> |cx:&'{context}mutContext<'{waker}>|{.. cx = yield ..} ...
layer2_tvl.entry(String::from("STARK")).or_insert(13.105); let stark_tvl = layer2_tvl.get("STARK"); match stark_tvl { Some(tvl) => println!("STARK TVL is {}",tvl), None => println!("STARK TVL is not found"), } }
If we know for sure that a spawned thread will definitely not outlive a certain scope, that thread could safely borrow things that do not live forever, such as local variables, as long as they outlive that scope. The Rust standard library provides thestd::thread::scopefunction to spawn such...
let year: Option = get_year("");if year.is_none() { println!("Invalid date given!");}Sometimes it’s useful to run some code only if a value is null, to ensure a variable has a non-null value. There are many ways to do it in Rust, but using match offers the most concise ...
No match in pre-checks; evaluating RuleSet rules... Initator EntityGroup matches: players Target EntityGroup matches: none Evaluating Rules... Checking direct initiator->target rules... No direct match rules found; continuing... Evaluating "players->any"... ...
Did you add an enum variant but forget to add that variant to amatchexpression? If you avoided using thematch all_expression, the compiler will tell you match arms aren't exhaustive and give you an error. Did a value that was previously always defined become nullable? Changing the type fro...