Getting the control variable from switch statement

the basic syntax of switch statement in ruby开发者_Python百科 is

case expression
  when condition1
    statements1
  when condition2
    statements2
  else
    statements
end

Is there a way to get control expression value in statements?

Means, is there some variable which stores expression value which can be used directly - and expression need not be called again in statements body?

There is no magic variable. It's no trouble to use an ordinary variable:

case a = expensive_method
  when condition1
    puts "#{a} meets condition 1"
  when condition2
    puts "#{a} meets condition 2"
end

No, there isn't. But you can just do this:

case var = expression
when condition1
  statements1
when condition2
  statements2 # use var whenever you like..
else
  statements
end

It's straightforward to assign the variable yourself inline:

case result = expression
when condition1
  result + 1
when condition2
  result + 2
else
  result
end