Check if not nil and not empty in Rails shortcut?

Solution 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.

Solution 2:

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.