如何在rails中添加条件类？

if condition
  # code to be executed if condition is true
else
  # code to be executed if condition is false
end

unless condition
  # code to be executed if condition is false
else
  # code to be executed if condition is true
end

case expression
when condition1
  # code to be executed if condition1 is true
when condition2
  # code to be executed if condition2 is true
else
  # code to be executed if no conditions are true
end