2.10. 代理模式¶
2.10.1. 目的¶
为昂贵或者无法复制的资源提供接口。
2.10.2. 例子¶
- Doctrine2 使用代理来实现框架特性(如延迟初始化),同时用户还是使用自己的实体类并且不会使用或者接触到代理
2.10.3. UML 图¶

2.10.4. 代码¶
你可以在 GitHub 上找到这些代码
BankAccount.php
1 2 3 4 5 6 7 8 9 10 | <?php declare(strict_types=1);
namespace DesignPatterns\Structural\Proxy;
interface BankAccount
{
public function deposit(int $amount);
public function getBalance(): int;
}
|
HeavyBankAccount.php
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 | <?php declare(strict_types=1);
namespace DesignPatterns\Structural\Proxy;
class HeavyBankAccount implements BankAccount
{
/**
* @var int[]
*/
private array $transactions = [];
public function deposit(int $amount)
{
$this->transactions[] = $amount;
}
public function getBalance(): int
{
// this is the heavy part, imagine all the transactions even from
// years and decades ago must be fetched from a database or web service
// and the balance must be calculated from it
return array_sum($this->transactions);
}
}
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BankAccountProxy.php
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 | <?php declare(strict_types=1);
namespace DesignPatterns\Structural\Proxy;
class BankAccountProxy extends HeavyBankAccount implements BankAccount
{
private ?int $balance = null;
public function getBalance(): int
{
// because calculating balance is so expensive,
// the usage of BankAccount::getBalance() is delayed until it really is needed
// and will not be calculated again for this instance
if ($this->balance === null) {
$this->balance = parent::getBalance();
}
return $this->balance;
}
}
|
2.10.5. 测试¶
ProxyTest.php
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 | <?php declare(strict_types=1);
namespace DesignPatterns\Structural\Proxy\Tests;
use DesignPatterns\Structural\Proxy\BankAccountProxy;
use PHPUnit\Framework\TestCase;
class ProxyTest extends TestCase
{
public function testProxyWillOnlyExecuteExpensiveGetBalanceOnce()
{
$bankAccount = new BankAccountProxy();
$bankAccount->deposit(30);
// this time balance is being calculated
$this->assertSame(30, $bankAccount->getBalance());
// inheritance allows for BankAccountProxy to behave to an outsider exactly like ServerBankAccount
$bankAccount->deposit(50);
// this time the previously calculated balance is returned again without re-calculating it
$this->assertSame(30, $bankAccount->getBalance());
}
}
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