CODEWITHSUNDEEP
rubyboolean-logic
pseudopeach
pseudopeach

Reputation: 1475

Ruby Newbie: Confused About Boolean Logic

I have an array, if I find a value in it, I want to execute a block of code. Also, if the array is nil, I want to execute that block. So the code I tried is:

if !array.respond_to? :index || array.index(str)
  #some code

So if it's nil it's true, or if str is somewhere in the array, it's true, right? But if it finds the item at index 0, it doesn't enter the block. Also, according to irb false || 0 evalueates to 0. WTF?? I thought that everything was true except false and nil. I guess || does something odd that I'm not expecting??

My questions are: What's going on? What's a nice way to write a conditional that does what I want?

Upvotes: 0

Views: 600

Answers (4)

Dave Newton
Dave Newton

Reputation: 160191

if array.nil? || array.member?(s)
    # ...

false || 0 evaluates to 0 because it's an or. False isn't truthy (obviously ;) but 0 is, so the expression is truthy.

Upvotes: 2

Sahil Muthoo
Sahil Muthoo

Reputation: 12496

Using nil? and include? with an inline if seems most idiomatic to me.

#your code if arr.nil? || arr.include?(str)

Upvotes: 2

Andy_Vulhop
Andy_Vulhop

Reputation: 4789

if array.nil?­ || array­.member?(str­)
    #code block
end

The || operator almost reminds you of a coalesce.

Given a = false, b = :bacon

return a || b #returns :bacon

Upvotes: 0

robotcookies
robotcookies

Reputation: 1059

Are you checking for a nil array or an empty one? If you've already declared the array it won't be nil even if it's empty. I'd write it like:

if array.empty? || array.include(str)

or if you really want to check for a nil array:

if array.nil? || array.include(str)

I'd use .include rather than .index to avoid getting a 0.

Upvotes: 0

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