rubymethod-missing

Method_missing not running when it should


I have a Team class in my program and I am trying to use method_missing but instead of running the function when the method doesn't exist, it gives me an error:"undefined method `hawks' for Team:Class (NoMethodError)"

My code is as follows:

class Team
  attr_accessor :cust_roster, :cust_total_per, :cust_name, :cust_best_player
  @@teams = []
  def initialize(stats = {})
    @cust_roster = stats.fetch(:roster) || []
    @cust_total_per = stats.fetch(:per)
    @cust_name = stats.fetch(:name)
    @cust_best_player = stats.fetch(:best)
    @@teams << self

  end
  def method_missing(methId)
    str = methID.id2name
    Team.new(roster:[], per: 0, name: str.uppercase, best: 0)

  end



  class <<self
    def all_teams
      @@teams
    end
  end

end
hawks = Team.hawks

Solution

  • There are a number of problems with your code. Let's go through one by one.

    From the documentation,

    method_missing(*args) private Invoked by Ruby when obj is sent a message it cannot handle.

    Here message refers to the method. In ruby, whenever you're calling a method on an object, you're actually sending a message to the object

    To better understand this, try this in the irb shell.

    1+2
    => 3
    1.send(:+,2)
    => 3
    

    Here 1 and 2 are objects of Fixnum class. You can confirm that by using 1.class. Ok, back to your question. So, a method_missing method should be called on an instance.

    team = Team.new
    team.hawks
    

    If you try the above piece of code, you'll get an error saying 'fetch': key not found: :roster (KeyError)

    You can get around this by passing a default value as the second parameter to fetch method. Replace your initialize method with

    def initialize(stats = {})
      @cust_roster = stats.fetch(:roster, [])
      @cust_total_per = stats.fetch(:per, 0)
      @cust_name = stats.fetch(:name, "anon")
      @cust_best_player = stats.fetch(:best, "anon")
      @@teams << self
    

    end

    If you execute the script, you'll get a stack level too deep (SystemStackError) because of a small typo in this line.

    str = methID.id2name
    

    In the method definition, you're receiving an argument with the name of methId but inside you're trying to call methID. Fix it with

    str = methId.id2name
    

    If you execute your script, you'll again get an error saying undefined method uppercase for "hawks":String (NoMethodError)

    This is because there is no uppercase method on strings. You should instead use the upcase method.

    Team.new(roster:[], per: 0, name: str.upcase, best: 0)
    

    and you should be good to go.

    For more, see http://apidock.com/ruby/BasicObject/method_missing

    Hope this helps!