Module method returns NoMethodError

I'm trying to create a method inside my module that returns a hash with the given parameters.

module MyModule

  def self.my_method(*search_params)
    # do something...

    end
    self
  end
end

I've seen a lot of similar questions about this, where the issue is because I'm defining an instance method, but I called self in the definition and continue receiving the error, leading me to believe it might be something else.

@example = { :name => 'John', :quote => 'Great fun!', :rank => 5 }
@example.my_method(:name => 'John') 

NoMethodError: undefined method `my_method` (NoMethodError)

Solution

We can't understand what your method is trying to do because the logic doesn't make sense but here's how you add your method to the Hash class.

module MyModule
  def my_method(*search_params)
    puts "search params: #{search_params}"
  end
end


class Hash
  include MyModule
end

@example = { :name => 'John', :quote => 'Great fun!', :rank => 5 }
@example.my_method(:name => 'John')

#=>search params: [{:name=>"John"}]

However this is called "monkey patching" which is not recommended. It would probably be better to use inheritance

module MyModule
  def monkey(*search_params)
    puts "search params: #{search_params}"
  end
end


class MonkeyHash < Hash
  include MyModule
end

@example = MonkeyHash.new(:name => 'John', :quote => 'Great fun!', :rank => 5)
@example.monkey(:name => 'John')

@example = { :name => 'John', :quote => 'Great fun!', :rank => 5 }

begin
  @example.monkey(:name => 'John')
rescue NoMethodError => e
  puts "Calling @exmaple.my_method raiesed: "
  puts e
  puts "@example is an instance of #{@example.class}. You may want to use MonkeyHash"
  puts "which includes the instance method 'monkey'"
end

Or you could define a singleton method

puts "let's try it with a singleton method\n\n"

@singleton_example = { :name => 'John', :quote => 'Great fun!', :rank => 5 }

@singleton_example.define_singleton_method(:monkey) do |*search_params|
  puts "search params: #{search_params}"
end

puts "now @example has the monkey method see: \n"
@singleton_example.monkey(:name => 'John')
puts "@singleton_example is still an instance of #{@singleton_example.class}"