Add event handler examples.

examples/event_handler_js/main.rs

@@ -0,0 +1,153 @@
+//! Implementation of the Event Handler With State Pattern - JS Style
+use rhai::{Dynamic, Engine, Map, Scope, AST};
+
+use std::io::{stdin, stdout, Write};
+
+const SCRIPT_FILE: &str = "event_handler_js/script.rhai";
+
+#[derive(Debug)]
+struct Handler {
+    pub engine: Engine,
+    pub scope: Scope<'static>,
+    pub states: Dynamic,
+    pub ast: AST,
+}
+
+fn print_scope(scope: &Scope) {
+    scope
+        .iter_raw()
+        .enumerate()
+        .for_each(|(i, (name, constant, value))| {
+            println!(
+                "[{}] {}{}{} = {:?}",
+                i + 1,
+                if constant { "const " } else { "" },
+                name,
+                if value.is_shared() { " (shared)" } else { "" },
+                *value.read_lock::<Dynamic>().unwrap(),
+            )
+        });
+    println!();
+}
+
+pub fn main() {
+    println!("Events Handler Example - JS Style");
+    println!("==================================");
+
+    let mut input = String::new();
+
+    // Read script file
+    print!("Script file [{}]: ", SCRIPT_FILE);
+    stdout().flush().expect("flush stdout");
+
+    input.clear();
+
+    stdin().read_line(&mut input).expect("read input");
+
+    let path = match input.trim() {
+        "" => SCRIPT_FILE,
+        path => path,
+    };
+
+    // Create Engine
+    let engine = Engine::new();
+
+    // Use an object map to hold state
+    let mut states = Map::new();
+
+    // Default states can be added
+    states.insert("bool_state".into(), Dynamic::FALSE);
+
+    // Convert the object map into 'Dynamic'
+    let mut states: Dynamic = states.into();
+
+    // Create a custom 'Scope' to hold state
+    let mut scope = Scope::new();
+
+    // Add any system-provided state into the custom 'Scope'.
+    // Constants can be used to optimize the script.
+    scope.push_constant("MY_CONSTANT", 42_i64);
+
+    // Compile the handler script.
+    println!("> Loading script file: {}", path);
+
+    let ast = match engine.compile_file_with_scope(&mut scope, path.into()) {
+        Ok(ast) => ast,
+        Err(err) => {
+            eprintln!("! Error: {}", err);
+            println!("Cannot continue. Bye!");
+            return;
+        }
+    };
+
+    println!("> Script file loaded.");
+    println!();
+    println!("quit      = exit program");
+    println!("scope     = print scope");
+    println!("states    = print states");
+    println!("event arg = run function with argument");
+    println!();
+
+    // Run the 'init' function to initialize the state, retaining variables.
+    let result = engine.call_fn_raw(&mut scope, &ast, false, true, "init", Some(&mut states), []);
+
+    if let Err(err) = result {
+        eprintln!("! {}", err)
+    }
+
+    // Create handler instance
+    let mut handler = Handler {
+        engine,
+        scope,
+        states,
+        ast,
+    };
+
+    // Events loop
+    loop {
+        print!("event> ");
+        stdout().flush().expect("flush stdout");
+
+        // Read event
+        input.clear();
+        stdin().read_line(&mut input).expect("read input");
+
+        let mut fields = input.trim().splitn(2, ' ');
+
+        let event = fields.next().expect("event").trim();
+        let arg = fields.next().unwrap_or("");
+
+        // Process event
+        match event {
+            "quit" => break,
+
+            "scope" => {
+                print_scope(&handler.scope);
+                continue;
+            }
+
+            "states" => {
+                println!("{:?}", handler.states);
+                println!();
+                continue;
+            }
+
+            // Map all other events to function calls
+            _ => {
+                let engine = &handler.engine;
+                let scope = &mut handler.scope;
+                let ast = &handler.ast;
+                let this_ptr = Some(&mut handler.states);
+
+                let result =
+                    engine.call_fn_raw(scope, ast, false, true, event, this_ptr, [arg.into()]);
+
+                if let Err(err) = result {
+                    eprintln!("! {}", err)
+                }
+            }
+        }
+    }
+
+    println!("Bye!");
+}

examples/event_handler_js/script.rhai

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+// Implementation of the Event Handler With State Pattern - JS Style
+
+/// Initialize user-provided state.
+fn init() {
+    // Can detect system-provided default states!
+    // Add 'bool_state' as new state variable if one does not exist
+    if !("bool_state" in this) {
+        this.bool_state = false;
+    }
+    // Add 'value' as new state variable (overwrites any existing)
+    this.value = 0;
+
+    // Can also add OOP-style functions!
+    this.log = |x| print(`State = ${this.value}, data = ${x}`);
+}
+
+/// 'start' event handler
+fn start(data) {
+    if this.bool_state {
+        throw "Already started!";
+    }
+    if this.value <= 0 {
+        throw "Conditions not yet ready to start!";
+    }
+    this.bool_state = true;
+    this.value += parse_int(data);
+
+    // Constant 'MY_CONSTANT' in custom scope is also visible!
+    print(`MY_CONSTANT = ${MY_CONSTANT}`);
+}
+
+/// 'end' event handler
+fn end(data) {
+    if !this.bool_state {
+        throw "Not yet started!";
+    }
+    if this.value > 0 {
+        throw "Conditions not yet ready to end!";
+    }
+    this.bool_state = false;
+    this.value = parse_int(data);
+}
+
+/// 'update' event handler
+fn update(data) {
+    let data = parse_int(data);
+    this.value += data;
+    this.log(data);
+}