如何在Ruby中使用哈希值

Question

I wrote a small Ruby program, but can't access the hash value stored in the parent class.

Here is the code:

class College
  @@dep = ["cs" => 60000, "mat" => 20000, "che" => 30000]
end

class Student < College
  def get_det
    puts "Enter name... \n"
    @name = gets
    puts "Enter department...\n"
    @dpt = gets
  end

  def set_fee
    case @dpt
    when "cs"
      @fee = (@@dep["cs"]).to_i
    when "mat"
      @fee = @@dep["mat"].to_i
    when "che"
      @fee = @@dep["che"].to_i
    else
      puts "Eror!!!"
    end
  end

  def print_det
    puts "Name : #{@name}"
    puts "Department : #{@dpt}"
    puts "Course fee : #{@fee}"
  end
end

det = Student.new

det.get_det
det.set_fee
det.print_det

I got the output as:

Output:

Answer 1

You've defined your @@dep variable as an array, not as a hash. You need to replace [ ] with { } , like so:

@@dep = {"cs" => 60000, "mat" => 20000, "che" => 30000}

Then you'll be able to access your hash values via the string keys:

@@dep['cs']  # Will return 6000

And just an FYI, your set_fee method could be refactored to just be this:

def set_fee
  @fee = @@dep[@dpt] || 'Error!'
  puts @fee
end

Since you're simply passing in the value you're checking against for each of your when statements, you can just pass the value directly to your @@dep object. And you don't need to_i , because the values in your hash are already integers.