本节对第三节的代码进行重构一下。
我们发现$.computed其实也是一种$.observable，因此可以写成这样：
var validValueType = $.oneObject("Null,NaN,Undefined,Boolean,Number,String")$.dependencyChain = (function () { var _frames = []; return { begin: function (ret) { _frames.push(ret); }, end: function () { _frames.pop(); }, collect: function (self) { if (_frames.length > 0) { self.list = self.list || []; var fn = _frames[_frames.length - 1]; if ( self.list.indexOf( fn ) >= 0) return; self.list.push(fn); } } };})();$.notifyUpdate = function(observable){ var list = observable.list if($.type(list,"Array")){ for(var i = 0, el; el = list[i++];){ el();//通知顶层的computed更新自身 } }}$.computed = function(obj, scope){ var args//构建一个至少拥有getter,scope属性的对象 if(typeof obj == "function"){ args = { getter: obj, scope: scope } }else if( typeof obj == "object" && obj && obj.getter){ args = obj } return $.observable(args, true)}$.observable = function(old, isComputed){ var cur, getter, setter, scope function ret(neo){ var set;//判定是读方法还是写方法 if(arguments.length){ //setter neo = typeof setter === "function" ? setter.call( scope, neo ) : neo set = true; }else{ //getter if(typeof getter === "function"){ $.dependencyChain.begin(ret);//只有computed才在依赖链中暴露自身 neo = getter.call( scope ) console.log(neo+"!!!!!!!!!!")//用来查看执行情况 $.dependencyChain.end() }else{ neo = cur } $.dependencyChain.collect(ret)//将暴露到依赖链的computed放到自己的通知列表中 } if(cur !== neo ){ cur = neo; $.notifyUpdate(ret) } return set ? ret : cur } if( isComputed == true){ getter = old.getter; setter = old.setter; scope = old.scope; ret();//必须先执行一次 }else{ old = validValueType[$.type(old)] ? old : void 0; cur = old;//将上一次的传参保存到cur中,ret与它构成闭包 ret(old);//必须先执行一次 } return ret}function MyViewModel() { this.firstName = $.observable('Planet'); this.lastName = $.observable('Earth'); this.fullName = $.computed({ getter: function () { return this.firstName() + " " + this.lastName(); }, setter: function (value) { var lastSpacePos = value.lastIndexOf(" "); if (lastSpacePos > 0) { // Ignore values with no space character this.firstName(value.substring(0, lastSpacePos)); // Update "firstName" this.lastName(value.substring(lastSpacePos + 1)); // Update "lastName" } }, scope: this }); this.card = $.computed(function(){ return this.fullName() +" 屌丝" },this); this.wordcard = $.computed(function(){ return this.card() +"工作卡 " },this) this.wordcardA = $.computed(function(){ return this.wordcard() +"A " },this)}window.onload = function(){ var model = new MyViewModel(); $.log("==================") model.lastName("last"); $.log("==================")} |
打印如下：
Planet Earth 屌丝!!!!!!!!!!Planet Earth 屌丝工作卡 !!!!!!!!!!Planet Earth!!!!!!!!!!Planet Earth 屌丝!!!!!!!!!!Planet Earth 屌丝工作卡 !!!!!!!!!!Planet Earth 屌丝工作卡 A !!!!!!!!!!==================Planet last!!!!!!!!!!Planet last!!!!!!!!!!Planet last 屌丝!!!!!!!!!!Planet last!!!!!!!!!!Planet last 屌丝!!!!!!!!!!Planet last 屌丝工作卡 !!!!!!!!!!Planet last!!!!!!!!!!Planet last 屌丝!!!!!!!!!!Planet last 屌丝工作卡 !!!!!!!!!!Planet last 屌丝工作卡 A !!!!!!!!!!================== |
依赖链发生效力了！不过感觉糟极了，有许多通知是没必要的。我们在$.notifyUpdate与$.observable添加缓存机制看看：
$.notifyUpdate = function(observable){ var list = observable.list; if($.type(list,"Array")){ for(var i = 0, el; el = list[i++];){ delete el.cache;//清除缓存 el();//通知顶层的computed更新自身 } } }//**********************略*************** $.observable = function(old, isComputed){//**********************略*************** function ret(neo){ var set;//判定是读方法还是写方法 if(arguments.length){ //setter neo = typeof setter === "function" ? setter.apply( scope, arguments ) : neo set = true; }else{ //getter if(typeof getter === "function"){ $.dependencyChain.begin(ret);//只有computed才在依赖链中暴露自身 if("cache" in ret){ neo = ret.cache;//从缓存中读取,防止递归 }else{ neo = getter.call( scope ); ret.cache = neo;//保存到缓存 console.log(neo+"!!!!!!!!!!");// } $.dependencyChain.end() }else{ neo = cur } $.dependencyChain.collect(ret)//将暴露到依赖链的computed放到自己的通知列表中 } if(cur !== neo ){ cur = neo; $.notifyUpdate(ret); } return set ? ret : cur }//**********************略*************** if( isComputed == true){ getter = old.getter; setter = old.setter; scope = old.scope; ret();//必须先执行一次 }else{ old = validValueType[$.type(old)] ? old : void 0; cur = old;//将上一次的传参保存到cur中,ret与它构成闭包 ret(old);//必须先执行一次 } return ret} |
这时它的情况就好多了：
PlanetEarthPlanet Earth!!!!!!!!!!Planet Earth 屌丝!!!!!!!!!!Planet Earth 屌丝工作卡 !!!!!!!!!!Planet Earth 屌丝工作卡 A !!!!!!!!!!==================Planet last!!!!!!!!!!Planet last 屌丝!!!!!!!!!!Planet last 屌丝工作卡 !!!!!!!!!!Planet last 屌丝工作卡 A !!!!!!!!!!================== |
标签: javascript, mass
