Ruby: No Block Given error

Question

I keep getting a 'no block given' error when trying to pass the string to the is_tut? method. I am new to Ruby and have no idea what I'm doing wrong. Any and all help would be appreciated.

class Tut
@@consonants = ["b","c","d","f","g","h","j","k","l","m","n","p","q","r","s","t","v","w","x","y","z"]

  def is_tut? string
    if string =~ /^(([b-df-hj-np-z]ut)|([aeiou\s])|[[:punct:]])+$/i
      yield
    else
      false
    end
  end

  def self.to_tut string 
        string.each_char do |c|
            c += "ut" if @@consonants.find { |i| i == c.downcase }
            yield c
        end
    end

    def self.to_english string
        array = string.split //
        array.each do |c|
            if @@consonants.find { |i| i == c.downcase }
                array.shift
                array.shift
            end
            yield c
        end
    end


end

#Tut.to_tut( "Wow! Look at this get converted to Tut!" ) { |c| print c }
# should output : Wutowut! Lutookut atut tuthutisut gutetut cutonutvuteruttutedut tuto Tututut!

puts
puts

tut = Tut.to_tut( "Wow! Look at this get converted to Tut!" )
puts "from return: #{tut}"

puts

#Tut.to_tut( "Wutowut! Lutookut atut tuthutisut gutetut cutonutvuteruttutedut tuto Tututut!" ) { |c| print c }
# should outout : Wutowut! Lutookut atut tuthutisut gutetut cutonutvuteruttutedut tuto Tututut!
puts
puts

#tut = Tut.to_tut( "Wutowut! Lutookut atut tuthutisut gutetut cutonutvuteruttutedut tuto Tututut!" )
#puts "from return: #{tut}"

puts

#tut_string = ""
#Tut.to_tut( "I'm in tut but I want to be in english." ) { |c| tut_string += c }
#puts tut_string
# should output : I'mut inut tututut bututut I wutanuttut tuto bute inut enutgutlutisuthut.

puts

#Tut.to_english( tut_string ) { |c| print c }
# should output : I'm in tut but I want to be in english.

Solution 1

If you have yield within your method definition, that means you have to obligatorily pass a block when you use it (unless the part including it is not executed according to conditioning etc.). (You might already know, but in case you don't: a block is something that is described as {...} or do ... end) And yield will refer to the block.

If you want to make a block optional, then one way to do it is to put the & symbol before the variable name.

def method(argument, &block_argument)
   if block_argument # block is given
      block_argument.call(argument_for_block) # use call to execute the block
   else # the value of block_argument becomes nil if you didn't give a block
      # block was not given
   end
end

This will allow optional block. Or, as suggested by Squeegy,

def method(argument)
   if block_given? # block is given
      yield(argument_for_block) # no need to use call to execute the block
   else 
      # block was not given
   end
end

will also work.

Solution 2

Because you're calling yield in your to_tut() method, this line will fail:

tut = Tut.to_tut( "Wow! Look at this get converted to Tut!" )

You either need to give a block (as you did in the first commented-out call to Tut.to_tut()), or you need to modify your to_tut() function to make the code block optional:

def self.to_tut string 
    string.each_char do |c|
        c += "ut" if @@consonants.find { |i| i == c.downcase }
        yield c if block_given?
    end
end

Comments

[PJP]

Just as a tip, a more Ruby-ish way to define your consonants would be: @@consonants = ('a' .. 'z').to_a - %w[a e i o u]

[Alex Wayne]

Or you could just use block_given? to something like yield if block_given?

[sawa]

That's another good way. block_given checks if there is a block, and if not, it returns false, and yield will not be executed, which means it will not cause an error.

[James Titus]

Sweet!! That worked! Thanks everyone! I may be back here with more questions later. Appreciate the help.