Declaring instance variables iterating over a hash!

Question

i want to do the following:

I want to declare the instance variables of a class iterating over a dictionary.

Let\'s assume that i have this hash

Answer 1

Chuck's answer is better than my last two attempts. The eigenclass is not self.class like I had thought; it took a better test than I had written to realize this.

Using my old code, I tested in the following manner and found that the class was indeed manipulated and not the instance:

a = MyClass.new :my_attr => 3
b = MyClass.new :my_other_attr => 4

puts "Common methods between a & b:"
c = (a.public_methods | b.public_methods).select { |v| a.respond_to?(v) && b.respond_to?(v) && !Object.respond_to?(v) }
c.each { |v| puts "    #{v}" }

The output was:

Common methods between a & b:
    my_other_attr=
    my_attr
    my_attr=
    my_other_attr

This clearly disproves my presupposition. My apologies Chuck, you were right all along.

Older answer:

attr_accessor only works when evaluated in a class definition, not the initialization of an instance. Therefore, the only method to directly do what you want is to use instance_eval with a string:

class MyClass
  def initialize(params)
    #hash = {"key1" => "value1","key2" => "value2","key3" => "value3"}
    params.each do |k,v|
      instance_variable_set("@#{k}", v)
      instance_eval %{
        def #{k}
          instance_variable_get("@#{k}")
        end
        def #{k}= (new_val)
          instance_variable_set("@#{k}", new_val)
        end
      }
    end
  end
end

To test this try:

c = MyClass.new :my_var => 1
puts c.my_var