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在ActionScript3中,如何将循环中数组的当前值传递给事件侦听器

scope loops actionscript-3 flex

1

Hooray Im Helping codaddict · 技术社区 · 16 年前

代码示例:

var gospels : Array = ["john", "mark", "matthew", "paul"];

for each (var book : String in gospels)
{
  var loader : URLLoader = new URLLoader();
  loader.load(new URLRequest("http://example.com/" + name));

  trace(book) // outputs current value of array

  loader.addEventListener(Event.COMPLETE, function(e : Event) : void {
    trace(book); // prints paul 4 times
  });
}

"john" , "mark" "matthew" ,及 "paul" ?

4 回复 | 直到 16 年前

1

4

Lior Cohen 16 年前

var gospels:Array = ["john", "mark", "matthew", "paul"];

for each (var item:String in gospels)
{
  (function(book:String){
    var loader : URLLoader = new URLLoader();
    loader.load(new URLRequest("http://example.com/" + name));

    trace(book) // outputs current value of array

    loader.addEventListener(Event.COMPLETE, function(e:Event):void {
      trace(book); // prints paul 4 times
    });
  }(item));
}

2

Vincent Osinga 16 年前

我认为更优雅的方法是编写URLLoader的超类,如:

class MyURLLoader extends URLLoader {
  public var book:String;

  function MyURLLoader(aBook:String){
    book = aBook;
    super();
  }
}

然后在循环中使用此类,如:

var gospels : Array = ["john", "mark", "matthew", "paul"];

for each (var book : String in gospels)
{
  var loader : MyURLLoader = new MyURLLoader(book);
  loader.load(new URLRequest("http://example.com/" + name));

  trace(book) // outputs current value of array

  loader.addEventListener(Event.COMPLETE, function(e : Event) : void {
    var myUrlLoader:MyURLLoader = e.target as MyURLLoader;
    trace (myUrlLoader.book);
  });
}

3

1

Markus Johnsson 16 年前

Michael Brewer Davis答案的一个变体,但这里使用Array.forEach,并以这种方式引入一个新变量 book 对于每个迭代:

var gospels : Array = ["john", "mark", "matthew", "paul"];

gospels.forEach(function (book: String, i: int, a: Array): void {
  var loader : URLLoader = new URLLoader();
  loader.load(new URLRequest("http://example.com/" + name));

  trace(book) // outputs current value of array

  loader.addEventListener(Event.COMPLETE, function(e : Event) : void {
    trace(book); 
  });
});

4

0

rzetterberg 16 年前

以下是最快和最好的结构化方法(imo):

var gospels:Array = ["john", "mark", "matthew", "paul"];

for(var book:String in gospels){ //For is faster than for each
    var loader:URLLoader = new URLLoader();
    //It's good practise to add the event listener before calling the function
    loader.addEventListener(Event.COMPLETE, loaderComplete(book), false, 0, true); 
    loader.load(new URLRequest("http://example.com/" + name));
}

function loaderComplete(book:String):Function{
    return function(event:Event):void{
        event.target.removeEventListener(Event.COMPLETE, arguments.callee);
        trace(book);
    }
}