Why do actions with class and public method don't fire __construct()

Question

I'm trying to understand how WordPress works with actions, classes, and methods.

If there is a class "TestClass" and it has a public method 'method1'

The method can be hooked to any action as "add_action('theHook', ['TestClass', 'method1']);"

From my understanding. If you don't initialize the class, you can not access its public methods and objects. Now, I would assume that WordPress has to follow this, and it must initialize my "TestClass", which will cause for public __construct() to fire.

However, after testing this, it does not fire __construct()..

Why is this?. I know a fix would be to self initialize inside 'method1', but I'm trying to figure out why WordPress behaves this way.

Answer 1

In these cases the methods are called statically. The class might look like this, note the static keyword:

class Foo 
{
    public static function bar()
    {
        echo "Hello, world!";
    }
}

And then you can register the callback like this:

add_action( 'hookname', ['Foo', 'bar'] );

There is no object instance, so no __construct() will be called. This is basically just a way to "name space" procedural functions.