Check if not nil and not empty in Rails shortcut?

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

2 Answers

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.

You can use .present? which comes included with ActiveSupport.

@city = @user.city.present?
# etc ...

You could even write it like this

def show %w(city state bio contact twitter mail).each do |attr| instance_variable_set "@#{attr}", @user[attr].present? end
end

It's worth noting that if you want to test if something is blank, you can use .blank? (this is the opposite of .present?)

Also, don't use foo == nil. Use foo.nil? instead.