Laravel 5 上下文中的命令和事件有什么区别

• Commands are things about to happen right now. i.e. "CreateUser"
• Events are things that have just occured right now - i.e. "UserSuccessfullyCreated"

这些差异看起来很小，但也有一些关键的差异.

• Commands must be specifically called/dispatched. I.e. if you want to do CommandX - you must call CommandX somewhere.
• 事件respond到应用程序中的事件触发anywhere.

让我们举个例子来最好地说明这一点.假设我们创建了一个用户，我们希望向他们发送一封欢迎邮箱，并更新我们的通讯列表.

In a Command Scenario would would do

AdminController {

    function create() {
            Bus::dispatch(new CreateUser(Auth::user());
    }
}

then in our CommandClass - we would do

public function handle(CreateUser $auth)
{
     // 1. Create the user here
     // 2. Send welcome email
     // 3. Update our newsletter
}

但如果我们使用事件，我们会在CommandClass中执行类似的操作

public function handle(CreateUser $auth)
    {
         // 1. Create the user here
         Event::fire(new UserWasCreated($user));
    }

然后，我们可以根据需要创建任意多个事件，并执行以下操作:

EventClassA

Event::listen('UserWasCreated', function($event)
{
    // 2. Send welcome email
});

EventClassB

Event::listen('UserWasCreated', function($event)
{
    // 3. Update our newsletter
});

最大的好处是分离关注点."createuser"命令现在不需要担心创建用户后会发生什么.它只需要CreateUser.

Also - if we want to add another function after a user signs up - say enter them in a lotto draw - you can just add another Event Class and add a new event listener.

EventClassC

Event::listen('UserWasCreated', function($event)
{
    // 4. Register them in lotto
});

Notice how we didnt need to touch the command CreateUser class code at all? This provides a true separation concerns of classes in a OOP style approach.