testable function

public function countrySelections(e:Event):Boolean {		
	var countryChanged:Boolean = false;
	var countries:ArrayCollection = e.currentTarget.selectedItems;
	trace("countrySelections:"+countries);
	var tmp:String = '';
  	for each(var i:Object in countries) {
        	    if(i.countryCode == 'All'){
        	    	tmp = 'All';
        	    	break;
        	    } else {
        	    	tmp+=i.countryCode+'|';
        	    }    
        }
        //Alert.show(myStrings.countryList + '___' + tmp);
        if(tmp != 'All'){
        	tmp = tmp.substring(0, tmp.lastIndexOf('|'));
        	if(myStrings.countryList.split('|').length > countries.length){
        		countryChanged = true;
        	} else {
        		for each(var j:Object in countries){
		        	if(myStrings.countryList.indexOf(j.countryCode) < 0 ){
		        		countryChanged = true;
		               }
        	        }
        	}        	
        } else {
        	if(myStrings.countryList != 'All') {countryChanged = true;}
        }        
        myStrings.countryList = tmp;        
        return countryChanged;
}

上面的函數是同事寫的，問題很多，其實主要的功能是myStrings.countryList 和e.currentTarget.selectedItems的比較。

1）首先可以把事件去掉

2）引用和改變了全局變量myStrings.countryList

3)兩個for,很多的if-else

其實這個問題可以簡化爲兩個排好序數組的比較,可見排序很重要

private function countrySelections2(c1:Array,c2:Array){
	return c1.sort().join("|")!=c2.sort().join("|")
}