状态模式

目的

根据对象的状态,对相同例行程序的不同行为进行封装。这是对象在运行时改变其行为的一种更简洁的方式,而不需要借助庞大的条件语句。

UML 类图

状态模式类图

代码

OrderContext.php

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<?php declare(strict_types = 1);

namespace DesignPatterns\Behavioral\State;

class OrderContext
{
private State $state;

public static function create(): OrderContext
{
$order = new self();
$order->state = new StateCreated();

return $order;
}

public function setState(State $state)
{
$this->state = $state;
}

public function proceedToNext()
{
$this->state->proceedToNext($this);
}

public function toString()
{
return $this->state->toString();
}
}

State.php

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<?php declare(strict_types = 1);

namespace DesignPatterns\Behavioral\State;

interface State
{
public function proceedToNext(OrderContext $context);

public function toString(): string;
}

StateCreated.php

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<?php declare(strict_types = 1);

namespace DesignPatterns\Behavioral\State;

class StateCreated implements State
{
public function proceedToNext(OrderContext $context)
{
$context->setState(new StateShipped());
}

public function toString(): string
{
return 'created';
}
}

StateShipped.php

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<?php declare(strict_types = 1);

namespace DesignPatterns\Behavioral\State;

class StateShipped implements State
{
public function proceedToNext(OrderContext $context)
{
$context->setState(new StateDone());
}

public function toString(): string
{
return 'shipped';
}
}

StateDone.php

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<?php declare(strict_types = 1);

namespace DesignPatterns\Behavioral\State;

class StateDone implements State
{
public function proceedToNext(OrderContext $context)
{
// there is nothing more to do
}

public function toString(): string
{
return 'done';
}
}

测试

Tests/StateTest.php

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<?php declare(strict_types = 1);

namespace DesignPatterns\Behavioral\State\Tests;

use DesignPatterns\Behavioral\State\OrderContext;
use PHPUnit\Framework\TestCase;

class StateTest extends TestCase
{
public function testIsCreatedWithStateCreated()
{
$orderContext = OrderContext::create();

$this->assertSame('created', $orderContext->toString());
}

public function testCanProceedToStateShipped()
{
$contextOrder = OrderContext::create();
$contextOrder->proceedToNext();

$this->assertSame('shipped', $contextOrder->toString());
}

public function testCanProceedToStateDone()
{
$contextOrder = OrderContext::create();
$contextOrder->proceedToNext();
$contextOrder->proceedToNext();

$this->assertSame('done', $contextOrder->toString());
}

public function testStateDoneIsTheLastPossibleState()
{
$contextOrder = OrderContext::create();
$contextOrder->proceedToNext();
$contextOrder->proceedToNext();
$contextOrder->proceedToNext();

$this->assertSame('done', $contextOrder->toString());
}
}