当前位置:免费学习网考试资料计算机类内容页

PHP中trait使用方法介绍

2021-09-12 16:39:24 计算机类 访问手机版

  PHP中trait使用方法介绍

  PHP中使用trait关键字是为了解决一个类既想集成基类的属性和方法,又想拥有别的基类的.方法,而trait一般情况下是和use搭配使用的。本文是小编搜索整理的关于PHP中trait使用方法介绍,感兴趣的朋友一起学习吧!!想了解更多相关信息请持续关注我们免费学习网!

  <?php

  trait Drive

  public $carName = 'trait';

  public function driving

  echo "driving $this->carName\n";

  class Person

  public function eat

  echo "eat\n";

  class Student extends Person

  use Drive;

  public function study

  echo "study\n";

  $student = new Student;

  $student->study;

  $student->eat;

  $student->driving;

  ?>

  输出结果如下:

  study

  eat

  driving trait

  上面的例子中,Student类通过继承Person,有了eat方法,通过组合Drive,有了driving方法和属性carName。

  如果Trait、基类和本类中都存在某个同名的属性或者方法,最终会保留哪一个呢?

  <?php

  trait Drive

  public function hello

  echo "hello drive\n";

  public function driving

  echo "driving from drive\n";

  class Person

  public function hello

  echo "hello person\n";

  public function driving

  echo "driving from person\n";

  class Student extends Person

  use Drive;

  public function hello

  echo "hello student\n";

  $student = new Student;

  $student->hello;

  $student->driving;

  ?>

  输出结果如下:

  hello student

  driving from drive

  因此得出结论:当方法或属性同名时,当前类中的方法会覆盖 trait的 方法,而 trait 的方法又覆盖了基类中的方法。

  如果要组合多个Trait,通过逗号分隔 Trait名称:

  use Trait1, Trait2;

  如果多个Trait中包含同名方法或者属性时,会怎样呢?答案是当组合的多个Trait包含同名属性或者方法时,需要明确声明解决冲突,否则会产生一个致命错误。

  <?php

  trait Trait1

  public function hello

  echo "Trait1::hello\n";

  public function hi

  echo "Trait1::hi\n";

  trait Trait2

  public function hello

  echo "Trait2::hello\n";

  public function hi

  echo "Trait2::hi\n";

  class Class1

  use Trait1, Trait2;

  ?>

  输出结果如下:

  代码如下:

  PHP Fatal error: Trait method hello has not been applied, because there are collisions with other trait methods on Class1 in ~/php54/trait_3.php on line 20

  使用insteadof和as操作符来解决冲突,insteadof是使用某个方法替代另一个,而as是给方法取一个别名,具体用法请看代码:

  <?php

  trait Trait1

  public function hello

  echo "Trait1::hello\n";

  public function hi

  echo "Trait1::hi\n";

  trait Trait2

  public function hello

  echo "Trait2::hello\n";

  public function hi

  echo "Trait2::hi\n";

  class Class1

  use Trait1, Trait2

  Trait2::hello insteadof Trait1;

  Trait1::hi insteadof Trait2;

  class Class2

  use Trait1, Trait2

  Trait2::hello insteadof Trait1;

  Trait1::hi insteadof Trait2;

  Trait2::hi as hei;

  Trait1::hello as hehe;

  $Obj1 = new Class1;

  $Obj1->hello;

  $Obj1->hi;

  echo "\n";

  $Obj2 = new Class2;

  $Obj2->hello;

  $Obj2->hi;

  $Obj2->hei;

  $Obj2->hehe;

  ?>

  输出结果如下:

  Trait2::hello

  Trait1::hi

  Trait2::hello

  Trait1::hi

  Trait2::hi

  Trait1::hello

  as关键词还有另外一个用途,那就是修改方法的访问控制:

  Trait 也能组合Trait,Trait中支持抽象方法、静态属性及静态方法,测试代码如下:

  <?php

  trait Hello

  public function sayHello

  echo "Hello\n";

  trait World

  use Hello;

  public function sayWorld

  echo "World\n";

  abstract public function getWorld;

  public function inc

  static $c = 0;

  $c = $c + 1;

  echo "$c\n";

  public static function doSomething

  echo "Doing something\n";

  class HelloWorld

  use World;

  public function getWorld

  return 'get World';

  $Obj = new HelloWorld;

  $Obj->sayHello;

  $Obj->sayWorld;

  echo $Obj->getWorld . "\n";

  HelloWorld::doSomething;

  $Obj->inc;

  $Obj->inc;

  ?>

  输出结果如下:

  Hello

  World

  get World

  Doing something

  1

  2