实现接口问题

Question

I have a type hint in the constructor but for some reason I get

Catchable fatal error: Argument 1 passed to Log::__construct() must be an instance of TestInterface, instance of Log\Handler given, called in 

TestInterface.php

namespace Log;  
    interface TestInterface
    {
      public function log();
    }

Handler.php

namespace Log;

require_once 'TestInterface.php';

use Log\TestInterface;

    class Handler implements TestInterface 
    {
      public function log() 
      {
        //some logic goes here 
      }
    }

Log.php

require_once 'Handler.php';

use Log\Handler;
class Log 
{
  public function __construct(TestInterface $handler)
  {
    $handler->log('test');
  }
}

$obj = new Log(new Handler());

So why do I get this error? I thought that when I implement the TestInterface the instance of Handler class will be passed through the Log constructor.

Answer 1

You have to add use Log\TestInterface; to the top of Log.php, because TestInterface is undefined in the global namespace. What you got back was not a helpful error message at all, but this should do it:

require_once 'Handler.php';

use Log\Handler;
use Log\TestInterface;

class Log 
{
  public function __construct(TestInterface $handler)
  {
    $handler->log('test');
  }
}

$obj = new Log(new Handler());