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// This Source Code Form is subject to the terms of the // Mozilla Public License, v. 2.0. If a copy of the MPL was // not distributed with this file, You can obtain one at // http://mozilla.org/MPL/2.0/. //! Crate which contains a "handler map", a structure that maps message types with "handlers" that //! can be called with them. //! //! The focal point of this crate is the `HandlerMap` type, which stores information about //! functions which receive various types. This can be used to encode event handlers, message //! handlers, or other situations where you want to dynamically select a function to call based on //! the data it receives. //! //! To register a handler, pass it to `insert`: //! //! ```rust //! use handler_map::HandlerMap; //! //! /// Message which prints to the console when received. //! struct MyMessage; //! //! fn handle(_: MyMessage) { //! println!("got your message!"); //! } //! //! let mut map = HandlerMap::new(); //! map.insert(handle); //! ``` //! //! This adds the handler to the map so that it can be `call`ed later on: //! //! ```rust //! # use handler_map::HandlerMap; //! //! # /// Message which prints to the console when received. //! # struct MyMessage; //! //! # fn handle(_: MyMessage) { //! # println!("got your message!"); //! # } //! //! # let mut map = HandlerMap::new(); //! # map.insert(handle); //! map.call(MyMessage); //! ``` //! //! The map can also take closures, as long as they implement `Fn` and don't capture any references //! to their environment: //! //! ```rust //! use handler_map::HandlerMap; //! use std::rc::Rc; //! use std::cell::Cell; //! //! /// Message which increments an accumulator when received. //! struct MyMessage; //! //! let mut map = HandlerMap::new(); //! let acc = Rc::new(Cell::new(0)); //! { //! let acc = acc.clone(); //! map.insert(move |_: MyMessage| { //! acc.set(acc.get() + 1); //! }); //! } //! //! // call the handler a few times to increment the counter //! map.call(MyMessage); //! map.call(MyMessage); //! map.call(MyMessage); //! //! assert_eq!(acc.get(), 3); //! ``` //! //! `call` can take a message of any type, even if that type hasn't been registered. It returns a //! `bool` representing whether a handler was called. If a handler for that type has been //! registered in the map, it returns `true`; otherwise, it returns `false`. If you want to check //! that a handler has been registered without calling it, use `is_registered` or //! `val_is_registered`. //! //! If you want to remove an event from the handler, call `remove`: //! //! ```rust //! use handler_map::HandlerMap; //! //! struct MyMessage; //! fn handle_msg(_: MyMessage) {} //! //! let mut map = HandlerMap::new(); //! map.insert(handle_msg); //! //! assert!(map.is_registered::<MyMessage>()); //! //! map.remove::<MyMessage>(); //! //! assert!(!map.is_registered::<MyMessage>()); //! ``` mod boxfn; use std::any::{Any, TypeId}; use std::collections::HashMap; use boxfn::{BoxFn, Opaque}; /// Struct that maps types with functions or closures that can receive them. /// /// See the [module-level documentation](index.html) for more information. #[derive(Default)] pub struct HandlerMap(HashMap<TypeId, BoxFn<'static, Opaque>>); impl HandlerMap { /// Creates a new map with no handlers. pub fn new() -> HandlerMap { Self::default() } /// Registers a new handler into the map. pub fn insert<T: Any, F: Fn(T) + 'static>(&mut self, handler: F) { let ptr: BoxFn<'static, T, F> = Box::new(handler).into(); let ptr: BoxFn<'static, Opaque> = ptr.erase().erase_arg(); let id = TypeId::of::<T>(); self.0.insert(id, ptr); } /// Un-registers the handler for the given type from this map. pub fn remove<T: Any>(&mut self) { let id = TypeId::of::<T>(); self.0.remove(&id); } /// Returns true if the given message type has a handler registered in the map. pub fn is_registered<T: Any>(&self) -> bool { let id = TypeId::of::<T>(); self.0.contains_key(&id) } /// Returns true if the given message has a handler registered in this map. /// /// This is the same operation as `is_registered`, but allows you to call it with a value /// rather than having to supply the type. pub fn val_is_registered<T: Any>(&self, _msg: &T) -> bool { self.is_registered::<T>() } /// Calls the handler with the given message, returning whether the handler was registered. pub fn call<T: Any>(&self, msg: T) -> bool { let id = TypeId::of::<T>(); if let Some(act) = self.0.get(&id) { unsafe { act.call_erased(msg); } true } else { false } } } #[cfg(test)] mod tests { use super::HandlerMap; #[test] fn it_works() { struct MyMessage; fn respond(_: MyMessage) {} let mut map = HandlerMap::new(); map.insert(respond); assert!(map.call(MyMessage)); } #[test] fn no_handler() { struct MyMessage; let map = HandlerMap::new(); assert!(!map.call(MyMessage)); } #[test] fn handler_is_called() { use std::sync::Arc; use std::sync::atomic::AtomicUsize; use std::sync::atomic::Ordering::SeqCst; let mut map = HandlerMap::new(); struct FancyCaller; let acc = Arc::new(AtomicUsize::new(0)); { let acc = acc.clone(); map.insert(move |_: FancyCaller| { acc.fetch_add(1, SeqCst); }); } map.call(FancyCaller); map.call(FancyCaller); map.call(FancyCaller); assert_eq!(acc.load(SeqCst), 3); } }