Defining struct in a class

ruby-talk
1

How can I properly define a struct in a class?

If I have

class Cards
    Card = Struct.new(:suit, :number)
    @cardsOnHand=[]

    @cardsOnHand.push(Card.new("S","5"))
end

This will give me an error message saying the push is not defined for
NilClass. How should I fix this?

···

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Posted via http://www.ruby-forum.com/.

2

The error you reported has nothing to do with your Card struct. Besides which, your code works for me as is.

···

On 2010-06-07 15:16:33 -0700, William Song said:

How can I properly define a struct in a class?

If I have

class Cards
    Card = Struct.new(:suit, :number)
    @cardsOnHand=

    @cardsOnHand.push(Card.new("S","5"))
end

This will give me an error message saying the push is not defined for
NilClass. How should I fix this?

--
Rein Henrichs

http://reinh.com

3

Rein Henrichs wrote:

This will give me an error message saying the push is not defined for
NilClass. How should I fix this?

The error you reported has nothing to do with your Card struct. Besides
which, your code works for me as is.

Sorry, I meant to put it into a function. I over-simplified it when
posted here.

class Cards
    Card = Struct.new(:suit, :number)
    @cardsOnHand=

    def a()
        @cardsOnHand.push(Card.new("S","5"))
    end
end

cards = Cards.new
cards.a()

The above code will give an error.

···

On 2010-06-07 15:16:33 -0700, William Song said:

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Posted via http://www.ruby-forum.com/\.

4

You create an instance variable, @cardsOnHand, in the class scope. That means it is an instance variable of the object Cards (the class). You then attempt to access it in the scope of an instance method, i.e. on a Cards instance. They are two different objects, two different scopes and two different variables.

I would suggest reading the chapter Classes, Objects and Variables in Programming Ruby: The Pragmatic Programmer's Guide to better understand the concept of scope in Ruby and how it effects variables. Hint: you probably want to set this instance variable when you *initialize* an Cards object.

I would also suggest reading styleguide/RUBY-STYLE at master · leahneukirchen/styleguide · GitHub to get a better grasp of common Ruby style, such as two space indention, adding spacing before and after the = in a variable assignment, using camel_case for variable and method names, and removing empty () on the ends of methods.

···

On 2010-06-07 16:16:57 -0700, William Song said:

Rein Henrichs wrote:

On 2010-06-07 15:16:33 -0700, William Song said:

This will give me an error message saying the push is not defined for
NilClass. How should I fix this?

The error you reported has nothing to do with your Card struct. Besides
which, your code works for me as is.

Sorry, I meant to put it into a function. I over-simplified it when
posted here.

class Cards
    Card = Struct.new(:suit, :number)
    @cardsOnHand=

    def a()
        @cardsOnHand.push(Card.new("S","5"))
    end
end

cards = Cards.new
cards.a()

The above code will give an error.

--
Rein Henrichs

http://reinh.com

5

I assume you want the first two lines of you class definition to be run every time someone creates an instance of you class. If you do you should put the into a method called initialize. That will be run automatically when new is called and should solve your problem

···

On 08/06/10 00:16, William Song wrote:

Rein Henrichs wrote:
   

On 2010-06-07 15:16:33 -0700, William Song said:

This will give me an error message saying the push is not defined for
NilClass. How should I fix this?
       

The error you reported has nothing to do with your Card struct. Besides
which, your code works for me as is.
     

Sorry, I meant to put it into a function. I over-simplified it when
posted here.

class Cards
     Card = Struct.new(:suit, :number)
     @cardsOnHand=

     def a()
         @cardsOnHand.push(Card.new("S","5"))
     end
end

cards = Cards.new
cards.a()

The above code will give an error.