Naming conventions for boolean attributes

I think of it like this:

• A boolean attribute should answer a simple yes/no question.
• Asking "is?" is a simple way to ask a yes/no question.
• So a boolean attribute name should complete the sentence is <attribute_name>
• Then just remove the is because Ruby prefers the ? suffix for "is"-style method names (see below for more), leaving you with just email_hidden

So, for your specific case, name your attribute like this:

• Start with the question "email is hidden"?. Which can be represented in code as: email_is_hidden.
• Remove the is and you're left with email_hidden
• Ruby on Rails defines a "predicate" version (one that ends in a ?) of your boolean attribute and returns true/false as expected. So, while your attribute is named email_hidden in the database you should reference it as email_hidden? in your code for clarity and as is the Ruby on Rails convention.

Taking these two examples of names you gave:

• hide_email would be a good name for a method performing such a task, a method that executes all the procedures to hide an email in the scope of your system. But it would never be a good name for a boolean method returning the state of an e-mail.
• email_hidden?, with a question mark (?) at the end, would be the correct name for a boolean method indicating if the e-mail is hidden or not.

Always consider Ruby conventions if you really want to write good code. They will help you even when thinking about the processes in your system.

That would be email_hidden?. It is what Ruby community got used to.

Please note the ? at the end.