feat(component): add once method (naver#434)

once is executed event just one time.

Ref naver#412
Close naver#412

src/component.js

@@ -112,6 +112,51 @@ eg.module("component", [eg], function(ns) {
 
 			return !isCanceled;
 		},
+		/**
+		 * Executed event just one time.
+		 * @ko 이벤트가 한번만 실행된다.
+		 * @method eg.Component#once
+		 * @param {eventName} eventName The name of the event to be attached <ko>등록할 이벤트의 이름</ko>
+		 * @param {Function} handlerToAttach The handler function of the event to be attached <ko>등록할 이벤트의 핸들러 함수</ko>
+		 * @return {eg.Component} An instance of a component itself<ko>컴포넌트 자신의 인스턴스</ko>
+		 * @example
+			var Some = eg.Class.extend(eg.Component,{
+				"hi": function(){
+					alert("hi");
+				},
+				"thing": function(){
+					this.once("hi",this.hi);
+				}
+			});
+
+			var some = new Some();
+			some.thing();
+			some.trigger("hi");
+			// fire alert("hi");
+			some.trigger("hi");
+			// Nothing happens
+		 */
+		once: function(eventName, handlerToAttach) {
+			if (typeof eventName === "object" &&
+			typeof handlerToAttach === "undefined") {
+				var eventHash = eventName;
+				var i;
+				for (i in eventHash) {
+					this.once(i, eventHash[i]);
+				}
+				return this;
+			} else if (typeof eventName === "string" &&
+				typeof handlerToAttach === "function") {
+				var self = this;
+				this.on(eventName, function listener() {
+					var arg = Array.prototype.slice.call(arguments);
+					handlerToAttach.apply(self, arg);
+					self.off(eventName, listener);
+				});
+			}
+
+			return this;
+		},
 		/**
 		 * Checks whether an event has been attached to a component.
 		 * @ko 컴포넌트에 이벤트가 등록됐는지 확인한다.

test/unit/js/component.test.js

@@ -376,4 +376,76 @@ test("The error should not occur without initialization of options property in S
 	}
 	//Then
 	ok(result);
-});
+});
+
+module("once method", {
+	setup : function(){
+		this.oClass = new TestClass({
+			"foo": 1,
+			"bar": 2
+		});
+	}
+});
+
+test("once method should be fire event one time.",function(){
+	//Given
+	var callCount = 0;
+	//When
+	this.oClass.once("test",function(){
+		callCount++;
+	});
+	this.oClass.trigger("test");
+	//Then
+	ok( callCount, 1);
+
+	//Given
+	//When
+	this.oClass.trigger("test");
+	//Then
+	ok( callCount, 1);
+});
+
+test("should be support object type.",function(){
+	//Given
+	var callCount = 0, callCount2 = 0;
+	//When
+	this.oClass.once({
+		"test": function(){
+			callCount++;
+		},
+		"test2": function(){
+			callCount2++;
+		}
+	});
+	this.oClass.trigger("test");
+	this.oClass.trigger("test2");
+	//Then
+	ok( callCount, 1);
+	ok( callCount2, 1);
+
+	//Given
+	//When
+	this.oClass.trigger("test");
+	this.oClass.trigger("test2");
+	//Then
+	ok( callCount, 1);
+	ok( callCount2, 1);
+});
+
+test("should be recevied parameters",function(){
+	//Given
+	var callCount = 0, e, a = {"a":1}, b = {"b":1}, param1;
+	this.oClass.once("test",function(event, aa){
+		callCount++;
+		e = event;
+		param1 = aa;
+	});
+
+	//When
+	this.oClass.trigger("test", a, b);
+
+	//Then
+	equal(a.a, e.a);
+	ok(typeof e.stop === "function");
+	equal(b, param1);
+});