在 php 中调用父方法的多种方法

起初我很困惑为什么构造函数中的两个方法调用都能正常工作，但现在我想我明白了。扩展类继承父类的方法，就好像它们是在类本身中声明的一样，而且这些方法存在于父类中，所以两者都应该可以工作。

现在我想知道是否有一种更好的方法(即最佳实践)来调用这个方法(通过 parent或 this) ，以及这些方法是否真的是相同的方法来执行相同的代码，或者在使用一种方法而不是另一种方法时是否有任何警告。

抱歉，我可能想太多了。

abstract class Animal {


function get_species() {


echo "test";


}


}


class Dog extends Animal {


function __construct(){


$this->get_species();
parent::get_species();


}


}


$spike = new Dog;
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Unless I am misunderstanding the question, I would almost always use $this->get_species because the subclass (in this case dog) could overwrite that method since it does extend it. If the class dog doesn't redefine the method then both ways are functionally equivalent but if at some point in the future you decide you want the get_species method in dog should print "dog" then you would have to go back through all the code and change it.

When you use $this it is actually part of the object which you created and so will always be the most up-to-date as well (if the property being used has changed somehow in the lifetime of the object) whereas using the parent class is calling the static class method.

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最佳答案

There are three scenarios (that I can think of) where you would call a method in a subclass where the method exists in the parent class:

  1. Method is not overwritten by subclass, only exists in parent.

This is the same as your example, and generally it's better to use $this -> get_species(); You are right that in this case the two are effectively the same, but the method has been inherited by the subclass, so there is no reason to differentiate. By using $this you stay consistent between inherited methods and locally declared methods.

  1. Method is overwritten by the subclass and has totally unique logic from the parent.

In this case, you would obviously want to use $this -> get_species(); because you don't want the parent's version of the method executed. Again, by consistently using $this, you don't need to worry about the distinction between this case and the first.

  1. Method extends parent class, adding on to what the parent method achieves.

In this case, you still want to use ``$this -> get_species();` when calling the method from other methods of the subclass. The one place you will call the parent method would be from the method that is overwriting the parent method. Example:

    abstract class Animal {


function get_species() {


echo "I am an animal.";
 

}


}


class Dog extends Animal {


function __construct(){


$this->get_species();
}


function get_species(){


parent::get_species();
echo "More specifically, I am a dog.";
}
}

The only scenario I can imagine where you would need to call the parent method directly outside of the overriding method would be if they did two different things and you knew you needed the parent's version of the method, not the local. This shouldn't be the case, but if it did present itself, the clean way to approach this would be to create a new method with a name like get_parentSpecies() where all it does is call the parent method:

function get_parentSpecies(){


parent::get_species();
}

Again, this keeps everything nice and consistent, allowing for changes/modifications to the local method rather than relying on the parent method.


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