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Rust method as function pointer
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| use std::collections::HashMap; | |
| macro_rules! handler { | |
| ($kernel:expr, $method:ident) => { | |
| Box::new(|x| $kernel.$method(x)) | |
| }; | |
| } | |
| fn main() { | |
| let k = Kernel::new(); | |
| k.recv("test".to_string(), "this is a test of the emergency broadcast system".to_string()); | |
| } | |
| struct Msg{ | |
| msg_type: String, | |
| msg: String | |
| } | |
| struct Kernel<'env> { | |
| handlers: HandlerCollection<'env> | |
| } | |
| impl Kernel<'_> { | |
| fn new() -> Self { | |
| let s = Self { | |
| handlers: HandlerCollection::new() | |
| }; | |
| s.handlers.add_handler(String::from("test"), handler!(s, test_handler)); | |
| s | |
| } | |
| fn recv(&self, msg_type: String, msg: String) { | |
| self.handlers.call(msg_type, msg) | |
| } | |
| pub fn test_handler(&self, msg: String) -> Result<(), &'static str> { | |
| println!("test msg: {}", msg); | |
| Ok(()) | |
| } | |
| } | |
| type HandlerFn<'env> = Box<dyn 'env + Fn(String) -> Result<(), &'static str>>; | |
| struct HandlerCollection<'env> { | |
| collection: HashMap<String, HandlerFn<'env>>, | |
| } | |
| impl HandlerCollection<'_> { | |
| fn new() -> Self { | |
| let mut s = Self { | |
| collection: HashMap::new(), | |
| }; | |
| s | |
| } | |
| fn add_handler(&mut self, name: String, handler: HandlerFn) { | |
| // cannot infer an appropriate lifetime due to conflicting requirements | |
| self.collection.insert(name, handler); | |
| } | |
| fn call(&self, msg_type: String, msg: String) { | |
| let handler = match self.collection.get(&msg_type) { | |
| Some(x) => x, | |
| None => { | |
| println!("no message handler found for message type: '{}'", msg_type); | |
| return; | |
| } | |
| }; | |
| match handler(msg) { | |
| Ok(()) => return, | |
| Err(e) => println!("error while handling {}: {}", msg_type, e), | |
| }; | |
| } | |
| } |
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