How can I add an error message for a validation method created in a class that extends GUMP?

[Joelfo]

I want to simply add a specific error message to appear if the validation function created inside the class return false. How can I do this? The instructions on the README.md do not seem to cover this issue.
Thanks!

[filisko]

@Joelfo yes it does cover it.

https://github.com/Wixel/GUMP#other-available-methods

// Set custom error messages for rules.
GUMP::set_error_message('required', '{field} is required.');
GUMP::set_error_messages([
    'required'    => '{field} is required.',
    'valid_email' => '{field} must be a valid email.'
]);

just replace GUMP with your class.

[j-masci]

I'm not understanding why the error messages are static, we should be able to set custom everything on a per-instance basis when needed. With extending the class and adding filter_* and validate_* methods, you can set custom filters/validators on a per instance basis, but then why do the error messages associated with those validators have to be global? I would like to be able to make a function that returns me a gump instance specific for my needs, without affecting all other gump instances used in the same project. I don't know if some reflection tricks can somehow accomplish this but its not something I've ever done. @filisko