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为什么在观察者模式中使用接口？(Why interface is used in observer pattern?)

 我在书中读到应用层应该独立于表示层。 设计模式就是这样的问题的解决方案。 当一个对象应该能够通知其他对象而不假设这些对象是谁时，观察者模式是适用的。但是像addObserver这样的方法会将观察者添加到观察者列表中。 之后，观察可以知道要通知哪些对象。 以及如何使用这些列表？ 在我读过的书中，它说可观察的只通过应用层中定义的接口访问观察者，以便保留系统的层结构。 然后界面使用该列表？ 如果是这样，有什么区别？ 

I have read in the book that the application layer is supposed to be independent of the presentation layer. Design pattern are solution to problem like that. Observer pattern is applicable when an object should be able to notify other objects without making assumptions about who those objects are.But a method such as addObserver adds the observers to the list of observers. After that, observerable know which objects are to be notified. And how those list are used? In the book I read, it said that the observerable only access observer through the interface defined in the application layer so that the layer architecture of the system is preserved. Then the interface use that list? lf so, what is the difference?

原文：https://stackoverflow.com/questions/38673403

更新时间：2023-02-01 16:02

最满意答案

<?php
$myarray =array ('black','blue','brown','yellow');
$row['color']='';
?>
<select name='whatever'>

<?php
    if ($row['color']=='' || $row['color']==null){
       echo "<option value=''>----Select----</option>";
    }
    foreach ($myarray as $color){

        if ($row['color']==$color){
            echo"<option value='$color' selected>$color</option>";
        }
        else{
            echo"<option value='$color'>$color</option>";
        }
     }
 ?>
 

<?php
$myarray =array ('black','blue','brown','yellow');
$row['color']='';
?>
<select name='whatever'>

<?php
    if ($row['color']=='' || $row['color']==null){
       echo "<option value=''>----Select----</option>";
    }
    foreach ($myarray as $color){

        if ($row['color']==$color){
            echo"<option value='$color' selected>$color</option>";
        }
        else{
            echo"<option value='$color'>$color</option>";
        }
     }
 ?>

为什么在观察者模式中使用接口？(Why interface is used in observer pattern?)

最满意答案

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