[5.2] Allow custom validators to be called with out function name

[joshhornby]

This would class based custom validators to simply call the class instead of having to define a function inside the class.

Validator::extend('postcode', PostcodeValidator::class);

[taylorotwell]

Typically we wouldn't call invoke but rather some convention like validate.

[GrahamCampbell]

surely it would be better to let php call that dynamically itself?

[joshhornby]

@taylorotwell

PostcodeValidator::class vs App\Validator\PostcodeValidator@validate

For me the ::class way is cleaner and easier to use with modern IDEs. Is there any reason not to allow both ways?

[taylorotwell]

I'm saying if you leave off the method we shouldn't call invoke, we should call validate.

[joshhornby]

Isn't this hiding magic inside the framework? Because if you call PostcodeValidator::class you'd expect it to call invoke?

[joshhornby]

@taylorotwell Ok, if we should call validate how do you feel about having an interface for custom validators to implement?

[taylorotwell]

Interface not needed. Just define the method.

[taylorotwell]

An interface would just be documentation at that point and waste loading time. If you don't define the method, you're going to get an error anyways. Embrace the dynamic nature of PHP :)