Check if not nil and not empty in Rails shortcut?

Question

I have a show page for my Users and each attribute should only be visible on that page, if it is not nil and not an empty string. Below I have my controller and it is quite annoying having to write the same line of code @user.city != nil && @user.city != "" for every variable. I am not too familiar with creating my own methods, but can I somehow create a shortcut to do something like this: @city = check_attr(@user.city)? Or is there a better way to shorten this procedure?

users_controller.rb

def show    @city = @user.city != nil && @user.city != ""   @state = @user.state != nil && @user.state != ""   @bio = @user.bio != nil && @user.bio != ""   @contact = @user.contact != nil && @user.contact != ""   @twitter = @user.twitter != nil && @user.twitter != ""   @mail = @user.mail != nil && @user.mail != "" end 

Answer 1

There's a method that does this for you:

def show   @city = @user.city.present? end 

The present? method tests for not-nil plus has content. Empty strings, strings consisting of spaces or tabs, are considered not present.

Since this pattern is so common there's even a shortcut in ActiveRecord:

def show   @city = @user.city? end 

This is roughly equivalent.

As a note, testing vs nil is almost always redundant. There are only two logically false values in Ruby: nil and false. Unless it's possible for a variable to be literal false, this would be sufficient:

if (variable)   # ... end 

This is preferable to the usual if (!variable.nil?) or if (variable != nil) stuff that shows up occasionally. Ruby tends to wards a more reductionist type of expression.

One reason you'd want to compare vs. nil is if you have a tri-state variable that can be true, false or nil and you need to distinguish between the last two states.