blocks|key|3427112|text|当在实例化上调用某些东西时，您需要一种方法来最终到达super。一种选择是在BMW上定义另一个调用super.printModel的方法|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|3427113|​|3427114|class+Car+{
++constructor(model)+{
++++this.model+=+model
++}
++printModel()+{
++++console.log(this.model)
++}
}

class+BMW+extends+Car+{
++constructor(model,+color)+{
++++super(model);
++++this.color+=+color
++}
++printModelBMW()+{
++++console.log(this.model,+this.color)
++}
++printModelCar()+{
++++super.printModel();
++}
}

let+bmw+=+new+BMW('F6',+'blue')
bmw.printModelBMW()+//will+print+:+'F6+blue'
bmw.printModelCar()+//+expected:+'F6'|code-block|syntax|javascript|3427115|3427116|entityMap^0|Q|5|12|3|1D|G|0|0|0|0^^$0|@$1|2|3|4|5|6|7|P|8|@$9|Q|A|R|B|C]|$9|S|A|T|B|C]|$9|U|A|V|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|W|8|@]|D|@]|E|$]]|$1|H|3|I|5|J|7|X|8|@]|D|@]|E|$K|L]]|$1|M|3|G|5|6|7|Y|8|@]|D|@]|E|$]]|$1|N|3|-4|5|6|7|Z|8|@]|D|@]|E|$]]]|O|$]]

<p>You'll need a way to eventually get to <code>super</code> when calling something on the instantiation. One option is to define another method on <code>BMW</code> that calls <code>super.printModel</code>:</p>

<p><div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
<div class="snippet-code">
<pre class="snippet-code-js lang-js prettyprint-override"><code>class Car {
  constructor(model) {
    this.model = model
  }
  printModel() {
    console.log(this.model)
  }
}

class BMW extends Car {
  constructor(model, color) {
    super(model);
    this.color = color
  }
  printModelBMW() {
    console.log(this.model, this.color)
  }
  printModelCar() {
    super.printModel();
  }
}

let bmw = new BMW('F6', 'blue')
bmw.printModelBMW() //will print : 'F6 blue'
bmw.printModelCar() // expected: 'F6'</code></pre>
</div>
</div>
</p>


blocks|key|1151506|text|super关键字只能在类内部使用，不能在外部使用。直接调用Car的printModel方法在技术上是可行的，但这确实应该避免。在超类(如printModel)中重写方法的全部目的是为了给它一个更适合于子类的实现。因此，绕过这一点表明不正确的OO设计。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1151507|然而，出于教育目的，我认为知道如何在技术上做到这一点仍然是有用的，因为它揭示了JS类实际上仍然在幕后使用原型：|1151508|Car.prototype.printModel.call(bmw)|code-block|syntax|javascript|1151509|改进设计以避免这种情况的一种方法是添加一个可选参数来指定打印模型的方式：|1151510|class+BMW+extends+Car{
++++constructor(model,+color){
++++++++super(model)
++++++++this.color+=+color
++++}
++++printModel(includeColor){
++++++++if+(includeColor)+{
++++++++++++console.log(this.model,+this.color)
++++++++}
++++++++else+super.printModel()
++++}
}|1151511|entityMap^0|0|5|T|3|X|A|1W|A|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@$9|T|A|U|B|C]|$9|V|A|W|B|C]|$9|X|A|Y|B|C]|$9|Z|A|10|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|11|8|@]|D|@]|E|$]]|$1|H|3|I|5|J|7|12|8|@]|D|@]|E|$K|L]]|$1|M|3|N|5|6|7|13|8|@]|D|@]|E|$]]|$1|O|3|P|5|J|7|14|8|@]|D|@]|E|$K|L]]|$1|Q|3|-4|5|6|7|15|8|@]|D|@]|E|$]]]|R|$]]

<p>The <code>super</code> keyword can only be used inside a class, not outside. It's technically possible to call <code>Car</code>'s <code>printModel</code> method directly, but this should really be avoided. The whole point of overriding a method in a superclass (like <code>printModel</code>) is to give it an implementation more appropriate to the subclass. So circumventing this is an indication of improper OO design.</p>

<p>However, for educational purposes I figure it would still be useful to know how this can technically be done, since it reveals how JS classes are really still using prototypes under the hood:</p>

<pre><code>Car.prototype.printModel.call(bmw)
</code></pre>

<p>One way to improve the design to avoid this would be to add an optional argument to specify how you want to print the model:</p>

<pre><code>class BMW extends Car{
    constructor(model, color){
        super(model)
        this.color = color
    }
    printModel(includeColor){
        if (includeColor) {
            console.log(this.model, this.color)
        }
        else super.printModel()
    }
}
</code></pre>


blocks|key|1151520|text|不可能在类的上下文之外引用超级实例。如果您确实必须从类外部使用来自超级实例的方法，您可以自己调用该方法：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1151521|Car.prototype.printModel.call(bmw);|code-block|syntax|javascript|1151522|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

<p>It's not possible to reference the super instance outside of the context of the class. If you really must use the method from the super instance from outside of the class, you can call the method yourself:</p>

<pre><code>Car.prototype.printModel.call(bmw);
</code></pre>


blocks|key|4896016|text|class+Car{
++++constructor(model){
+++++++this.model+=+model
++++}
++++printModel(){
++++console.log(this.model)
++++}
+++getModel()
++{
++++++return+this.model
++}

+}

++class+BMW+extends++Car{
++++++constructor(model,+color){
++++++++super(model);
+++++++++this.color+=+color
+++++}
+++++printModel(){
+++++++++console.log(super.getModel(),+this.color)
+++++}
}|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|4896017|unstyled|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|G|8|@]|9|@]|A|$B|C]]|$1|D|3|-4|5|E|7|H|8|@]|9|@]|A|$]]]|F|$]]

<pre><code>class Car{
    constructor(model){
       this.model = model
    }
    printModel(){
    console.log(this.model)
    }
   getModel()
  {
      return this.model
  }

 }

  class BMW extends  Car{
      constructor(model, color){
        super(model);
         this.color = color
     }
     printModel(){
         console.log(super.getModel(), this.color)
     }
}
</code></pre>


blocks|key|4896034|text|如果父类方法需要与子类方法一起使用，这意味着类设计出错，覆盖父方法是错误的。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4896035|可能是：|4896036|class+Car{
++++...
++++printGenericModel(){
++++++++console.log(this.model)
++++}
}

class+BMW+extends+Car{
++++...
++++printModel(){
++++++++console.log(this.model,+this.color)
++++}
}|code-block|syntax|javascript|4896037|或者在父类无法重构的情况下：|4896038|class+Car{
++++...
++++printModel(){
++++++++console.log(this.model)
++++}
}

class+BMW+extends+Car{
++++...
++++get+printGenericModel(){
++++++++return+super.printModel;
++++}
++++printModel(){
++++++++console.log(this.model,+this.color)
++++}
}|4896039|在BMW实例上，这两种方法都以printGenericModel和printModel的形式提供。|offset|length|style|CODE|4896040|entityMap^0|0|0|0|0|0|1|3|F|H|X|A|0^^$0|@$1|2|3|4|5|6|7|U|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|V|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|W|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|X|8|@]|9|@]|A|$]]|$1|K|3|L|5|F|7|Y|8|@]|9|@]|A|$G|H]]|$1|M|3|N|5|6|7|Z|8|@$O|10|P|11|Q|R]|$O|12|P|13|Q|R]|$O|14|P|15|Q|R]]|9|@]|A|$]]|$1|S|3|-4|5|6|7|16|8|@]|9|@]|A|$]]]|T|$]]

<p>If parent class method needs to be used alongside with child class method, this means class design went wrong, overriding parent method was a mistake.</p>

<p>It could be:</p>

<pre><code>class Car{
    ...
    printGenericModel(){
        console.log(this.model)
    }
}

class BMW extends Car{
    ...
    printModel(){
        console.log(this.model, this.color)
    }
}
</code></pre>

<p>Or in case parent class can't be refactored:</p>

<pre><code>class Car{
    ...
    printModel(){
        console.log(this.model)
    }
}

class BMW extends Car{
    ...
    get printGenericModel(){
        return super.printModel;
    }
    printModel(){
        console.log(this.model, this.color)
    }
}
</code></pre>

<p>Both methods are available as <code>printGenericModel</code> and <code>printModel</code> on <code>BMW</code> instance.</p>


<p>I have a class BMW that extends the  class Car and override a method printModel:</p>

<p><div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
<div class="snippet-code">
<pre class="snippet-code-js lang-js prettyprint-override"><code>class Car{
    constructor(model){
        this.model = model
    }
    printModel(){
        console.log(this.model)
    }
}

class BMW extends  Car{
    constructor(model, color){
        super(model);
        this.color = color
    }
    printModel(){
        console.log(this.model, this.color)
    }
}

let bmw = new BMW('F6', 'blue')
bmw.printModel() //will print : 'F6 blue'
bmw.super.printModel()// expected: 'F6' but not working</code></pre>
</div>
</div>
</p>

<p>How to call a class super  method on an instance of this BMW class?</p>


How to call a super class method outside a class?

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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我有一个类BMW，它扩展了类Car并覆盖了一个方法printModel：​class Car{    constructor(model){        this.model = model    }    printModel(){        console.log(this.model)    }}class...

问如何在类外调用超类方法？
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问如何在类外调用超类方法？EN