Method referring to a pulled in packaged's met

问题:

When I put a method that refers to a pulled in package inside another method it leaves scope and fails.

What is the proper way to do this. I tried playing with the 'self' but am new and that did not work out.

Desired solution. Does not work. Returns error.

undefined method `accounts' for nil:NilClass (NoMethodError)

require 'package that has 'accounts''


class Name

    @sandbox = #working API connection

    def get_account
        @sandbox.accounts do |resp|         #This is where error is
          resp.each do |account|

            if account.name == "John"
                name = account.name
            end

          end
        end
    end


end


new = Name.new
p new.get_account

---

This works but does not create a reusable method.

require 'package that has 'accounts''

class Name

    @sandbox = #working API connection


        @sandbox.accounts do |resp|       
          resp.each do |account|    
            if account.name == "John"
                p account.name
            end
          end
        end




end


new = Name.new

回答1:

1. The mistake in the code is that @sandbox is an attribute of the class. The value would be initialized when an object of the class is created. Writing the initialization in the class will have no effect. @Maxim has explained this in his answer.

2. For the second code, when the interpreter runs through the code, it would execute it once. But that code cannot run more than once.

The code should be,

require 'package that has 'accounts''


class Name

    def initialize
      @sandbox = #working API connection
    end

    def get_account
        @sandbox.accounts do |resp|         #This is where error is
          resp.each do |account|

            if account.name == "John"
                name = account.name
            end

          end
        end
    end


end


new = Name.new
p new.get_account

回答2:

To understand this, you need to understand the concept of singleton classes in Ruby.

The class Name is an object itself, and @sandbox is an instance variable of that object.

If you write def self.get_account you could use @sandox there, but then this method is not available for instances of Name, e.g. you should call Name.get_account and not Name.new.get_account. Actually, this adds a method to the singleton class of Name, and that's why you can access @sandbox there.

To create an instance variable that could be used in the instances of Name, you should do so in the initialize method of Name.