《PHP实例:PHP中trait使用方法详细介绍》要点:
本文介绍了PHP实例:PHP中trait使用方法详细介绍,希望对您有用。如果有疑问,可以联系我们。
PHP实例说通俗点,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.
- PHP实例
- <?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();
- ?>
PHP实例输出结果如下:
- PHP实例
- study
- eat
- driving trait
PHP实例上面的例子中,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.
PHP实例如果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实例
- <?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();
- ?>
PHP实例输出结果如下:
- PHP实例
- hello student
- driving from drive
PHP实例因此得出结论: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.
PHP实例如果要组合多个Trait,通过逗号分隔 Trait名称:
- PHP实例
- use Trait1, Trait2;
PHP实例如果多个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实例
- <?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;
- }
- ?>
PHP实例输出结果如下:
PHP实例使用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实例
- <?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();
- ?>
PHP实例输出结果如下:
- PHP实例
- Trait2::hello
- Trait1::hi
- Trait2::hello
- Trait1::hi
- Trait2::hi
- Trait1::hello
PHP实例as关键词还有另外一个用途,那就是修改方法的访问控制:
PHP实例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实例
- <?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();
- ?>
PHP实例输出结果如下:
- PHP实例
- Hello
- World
- get World
- Doing something
- 1
- 2
PHP实例以上就是本文的全部内容,希望对大家的学习有所帮助,也希望大家多多支持维易PHP.
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