initial implementation of events#once

spec/suites/core/EventsSpec.js

@@ -245,4 +245,66 @@ describe('Events', function() {
 			expect(spy3.called).to.be(true);
 		});
 	});
+
+	describe('#once', function(){
+		it('removes event listeners after first fire', function() {
+			var obj = new Klass(),
+				spy = new sinon.spy();
+
+			obj.once('test', spy);
+			obj.fire('test');
+
+			expect(spy.called).to.be(true);
+
+			obj.fire('test');
+
+			expect(spy.callCount).to.be.lessThan(2);
+		});
+
+		it('works with object hash', function() {
+			var obj = new Klass(),
+				spy = new sinon.spy(),
+				otherSpy = new sinon.spy();
+
+			obj.once({
+				test: spy,
+				otherTest: otherSpy
+			});
+
+			obj.fire('test');
+			obj.fire('otherTest');
+
+			expect(spy.called).to.be(true);
+			expect(otherSpy.called).to.be(true);
+
+			obj.fire('test');
+			obj.fire('otherTest');
+
+			expect(spy.callCount).to.be.lessThan(2);
+			expect(otherSpy.callCount).to.be.lessThan(2);
+		});
+
+		it('only removes the fired event handler', function(){
+			var obj = new Klass(),
+				spy = new sinon.spy(),
+				otherSpy = new sinon.spy();
+
+			obj.once({
+				test: spy,
+				otherTest: otherSpy
+			});
+
+			obj.fire('test');
+
+			expect(spy.called).to.be(true);
+			expect(otherSpy.called).to.be(false);
+
+			obj.fire('otherTest');
+
+			expect(otherSpy.called).to.be(true);
+
+			expect(spy.callCount).to.be.lessThan(2);
+			expect(otherSpy.callCount).to.be.lessThan(2);
+		});
+	});
 });

src/core/Events.js

@@ -148,6 +148,29 @@ L.Mixin.Events = {
 		}
 
 		return this;
+	},
+
+	once: function(types, fn, context) {
+		handlerFor = function(fn, type, context) {
+			var handler = function() {
+				this.removeEventListener(type, fn, context);
+				this.removeEventListener(type, handler, context);
+			}
+			return handler;
+		}
+
+		if (typeof types === 'object') {
+			for (type in types) {
+				if (types.hasOwnProperty(type)) {
+					this.addEventListener(type, types[type], fn);
+					this.addEventListener(type, handlerFor(types[type], type, fn), fn);
+				}
+			}
+			return this;
+		}
+
+		this.addEventListener(types, fn, context);
+		return this.addEventListener(types, handlerFor(fn, types, context), context);
 	}
 };