CODEWITHSUNDEEP
ruby
Scott
Scott

Reputation: 303

Multi-parameter case

I want to create a case checking multiple parameters.

"Ruby: conditional matrix? case with multiple conditions?" is basically it with one twist: The second parameter can be one of three values, a, b, nil.

I was hoping to just extend the when conditions to be something like:

 result = case [A, B]
  when [true, ‘a’] then …
  when [true, ‘b’] then …
  when [true, B.nil?] then …
end

Any suggestions?

Upvotes: 0

Views: 73

Answers (1)

knut
knut

Reputation: 27855

In the comments is already the answer for your specific test for nil:

result = case [A, B]
  when [true, 'a'] then …
  when [true, 'b'] then …
  when [true, nil] then …
end

But your question inspired me for a more extended question: What if the 2nd parameter could be anything? E.g. you have this decision table:

A   B   result
------------------
a   b   true
a   _   halftrue
_   b   halftrue
else    false

where _ is a indicator for anything

A possible solution would be a class, that is equal to everything:

class Anything
  include Comparable
  def <=>(x);0;end
end

[
  %w{a b},
  %w{a x},
  %w{x b},
  %w{x y},
].each{|a,b|

  result = case [a, b]
    when ['a', 'b'] then true
    when ['a', Anything.new] then :halftrue
    when [Anything.new, 'b'] then :halftrue
    else false
  end

  puts "%s %s: %s" % [a,b,result]
}

The result:

a b: true
a x: halftrue
x b: halftrue
x y: false

Upvotes: 1

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