NiN

Command

7/16/2021 OOPPatternBehavioral pattern

# Description

Command is behavioral design pattern that converts requests or simple operations into objects.

  • Chuyển request thành object

# Example

Xử lí lưu post với các trạng thái yêu cầu là draft, no approval, pusblish,..

  1. Class xử lí business logic cho post:

    class PostReceiver
{
	public function draft() 
	{
		// do something
	}
    
    public function noApproval() 
	{
		// do something
	}
    
    public function publish() 
	{
		// do something
	}
}
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  2. Command:

    interface Command
{
	public function excute();
}
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  3. Concreate command: class implement command define thực thi của Receiver tương ứng với case request.

    class DraftCommand implements Command
{
    protected PostReceiver $receiver;

    public function __construct(PostReceiver $receiver)
    {
        $this->receiver = $receiver;
    }

    public function execute()
    {
        $this->receiver->saveDraft();
    }
}
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    class NoApprovalCommand implements Command
{
    protected PostReceiver $receiver;

    public function __construct(PostReceiver $receiver)
    {
        $this->receiver = $receiver;
    }

    public function execute()
    {
        $this->receiver->saveNoApproval();
    }
}
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    class PublishCommand implements Command
{
    protected PostReceiver $receiver;

    public function __construct(PostReceiver $receiver)
    {
        $this->receiver = $receiver;
    }

    public function execute()
    {
        $this->receiver->savePublish();
    }
}
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  4. Invoker: Liên kết với command, gửi request đến command.

    class Invoker
{
    private Command $command;

    public function setCommand(Command $cmd)
    {
        $this->command = $cmd;
    }

    public function run()
    {
        $this->command->execute();
    }
}
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  5. Usage:

    $invoker = new Invoker();
$postReceiver = new PostReceiver();

$invoker->setCommand(new DraftCommand($postReceiver));
$invoker->run();
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→ Dễ dàng thêm các command mới mà vẫn tuân thủ Open/Closed Principle . → Dễ thực hiện unit testing.