PHP怎样使用Trait代码复用？特性用法解析

<?php

// 定义一个处理日志的Trait
trait LoggerTrait {
    private string $logPrefix = "[APP]";

    public function log(string $message): void {
        echo $this->logPrefix . " " . date('Y-m-d H:i:s') . ": " . $message . "\n";
    }

    public function setLogPrefix(string $prefix): void {
        $this->logPrefix = $prefix;
    }
}

// 定义一个处理缓存的Trait
trait CacheTrait {
    public function setCache(string $key, $value): void {
        echo "Caching key '{$key}' with value '{$value}'\n";
    }

    public function getCache(string $key) {
        echo "Retrieving cache for key '{$key}'\n";
        return "cached_value_for_{$key}"; // 模拟返回
    }
}

// 一个服务类，需要日志和缓存能力
class UserService {
    use LoggerTrait;
    use CacheTrait;

    public function createUser(string $username): void {
        $this->log("Attempting to create user: " . $username);
        // ... 创建用户逻辑 ...
        $this->setCache("user_{$username}", ['status' => 'created']);
        $this->log("User '{$username}' created successfully.");
    }
}

// 另一个处理订单的类，也需要日志能力
class OrderService {
    use LoggerTrait; // 只需要日志能力

    public function createOrder(string $orderId): void {
        $this->log("Processing order: " . $orderId);
        // ... 订单处理逻辑 ...
        $this->log("Order '{$orderId}' completed.");
    }
}

$userService = new UserService();
$userService->setLogPrefix("[USER]"); // 可以修改Trait内部属性
$userService->createUser("Alice");
$userService->getCache("user_Alice");

echo "--------------------\n";

$orderService = new OrderService();
$orderService->log("Starting order service operations.");
$orderService->createOrder("ORD-2023-001");

?>

OrderService

Notification

NotifierTrait

<?php
trait A {
    public function hello() {
        echo "Hello from Trait A!\n";
    }
}

trait B {
    public function hello() {
        echo "Hello from Trait B!\n";
    }
}

class MyClass {
    use A, B {
        // 解决冲突：指定使用Trait B的hello方法
        B::hello insteadof A;
        // 也可以给Trait A的hello方法起个别名，让两个方法都能用
        A::hello as helloFromA;
    }

    public function hello() {
        echo "Hello from MyClass!\n";
    }
}

$obj = new MyClass();
$obj->hello(); // 输出：Hello from MyClass! (类自身方法优先级最高)
$obj->helloFromA(); // 输出：Hello from Trait A! (通过别名调用)

// 如果MyClass中没有定义hello方法，并且只use A, B { B::hello insteadof A; }
// 那么 $obj->hello(); 会输出 "Hello from Trait B!"
?>

B::hello insteadof A;

as

A::hello as helloFromA;

$obj->helloFromA()

implements

CacheInterface

set()

get()

extends

AbstractShape

getColor()

getArea()

Circle

Rectangle