[SOLVED] Ruby unless vs if logic

Ruby unless vs if logic

Can someone please explain this behavior? Why does nil return true when result = true if i but returns false when result = false unless i

unless case screenshot

def my_all?(pattern = nil)
result = true
my_each do |i|
  case pattern
  when nil
    p result, i
    result = false unless i
  when Regexp
    result = false unless i.to_s.match(pattern)
  when Class
    result = false unless i.is_a?(pattern)
  when String, Numeric
    result = false unless i == pattern   
  end
  result = yield(i) if block_given? && pattern.nil?
  break if !result
end
  result
end

if case screenshot

def my_all?(pattern = nil)
    result = false
    my_each do |i|
      case pattern
      when nil
        p result, i
        result = true if i
      when Regexp
        result = true if i.to_s.match(pattern)
      when Class
        result = true if i.is_a?(pattern)
      when String, Numeric
        result = true if i == pattern   
      end
      result = yield(i) if block_given? && pattern.nil?
      break if !result
    end
    result
  end

Solution

In your second example, once result is set to true, nothing ever sets it to false again. So if the first value yielded from my_each is truthy, then the my_all? method will return true.

This second example seems like more like an implementation of any?, rather than all?. Except it is actually only checking the first element. If the first i is falsey, then the loop will be broken and it will return false. If the first i is truthy, then it will be set to true and nothing will set it back to false, and the method will return `true.

See these two examples, where the only difference is the values yielded by my_each: