Shortening an if-else structure in Ruby

Question

I have written something like this, the same if-else logic I knew from Visual Basic 6.0, but I am sure there is a better "Ruby way" of writing it.

Can you please show me how it would look like in Ruby world?

  if params[:medication_name].nil?
    med_name = 'all'
  elsif params[:medication_name] == 'undefined'
    med_name = 'all'
  else
    med_name = params[:medication_name]
  end

Not really a better "ruby way" but you could try a ternary statement. — Vigrant, Aug 15 '13 at 17:40
Side note: it is a best-practice in Ruby to move your assignment to the result of the conditional. https://gist.github.com/anonymous/bf0ba38c44968399766ada48076c9222 — Tyler Willingham, Jun 20 '17 at 20:43

Michael Geary · Answer 1 · 2013-08-15T17:48:29.900

8

There are several different ways you could simplify this, for example:

med_name = params[:medication_name]
med_name = 'all' if med_name.nil? or med_name == 'undefined'

edited Aug 15 '13 at 17:48

answered Aug 15 '13 at 17:42

Michael Geary

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score 4 · Accepted Answer · answered Aug 15 '13 at 17:46

For your case, something like this:

med_name = params[:medication_name] 
med_name = 'all' if [nil, 'undefined'].include? med_name

For more general long chains of if/elsif/else, look at case statements. They're overkill in this case, but here's an example:

med_name = case params[:med_name]
   when 'undefined', nil 
     'all'
   else
      params[:med_name]
end

score 2 · Answer 3 · answered Aug 17 '13 at 01:13

2

Unique to Ruby:

med_name = {nil=>'all', 'undefined'=>'all'}[params[:medication_name]] || params[:medication_name]

answered Aug 17 '13 at 01:13

jaeheung

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Arup Rakshit · Answer 4 · 2013-08-15T18:10:32.717

1

you can do as below :

val = [nil, 'undefined'].include?(params[:medication_name]) ? "all" : params[:medication_name]

edited Aug 15 '13 at 18:10

answered Aug 15 '13 at 17:46

Arup Rakshit

113,563
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Arman H · Answer 5 · 2013-08-15T18:21:56.063

Using case statements is a Ruby-friendly way. If you're checking against one value, you can do:

case params[:medication_name]
    when nil?
        med_name = 'all'
    when 'undefined'
        med_name = 'all'
    else
        med_name = params[:medication_name]
end

Another way is to test against multiple values:

foo = true
bar = false
case
    when foo == true
        puts "foo is true"
    when foo == false
        puts "foo is false"
    when bar == true
        puts "bar is true"
    when bar == false
        puts "bar is false"
    else
        puts "foo and bar are neither true or false!"
end

Shortening an if-else structure in Ruby

5 Answers5