Adding object to array of arrays

Question

I am trying to add an object to an array of arrays, but when i do, i am recieving an error in my array of array unit tests, stating :- "undefined method 'has_key' for nil:NilClass". However, if i try and add a string or number to the array of array, it works absolutely fine.

I set up my array of arrays like this

@array_of_array= Array.new(5) { Array.new(3) }

Now if I try to do this

@array_of_array[0][0] = MyObject.new

Then if I run my unit tests against @array_of_array, i get the error.

But if I try to do this

@array_of_array[0][0] = 'Test'

Theres no problem.

--Edited---

Heres failing test

it "should place object in correct starting position" do
array_of_array= Array.new(5) { Array.new(3) }
array_of_array[1][0] = MyObject.new
array_of_array.should eql('fail on purpose..want to see output')

end

Im new to ruby, so unsure of where im going wrong. Thanks

Works for me. has_key is a method called on a Hash, not an Array, so can you paste the stack trace? — tadman
– tadman, Commented Oct 21, 2011 at 16:46
@namtax: That would indicate that the problem lies with MyObject.new rather than with the array. — Claw
– Claw, Commented Oct 21, 2011 at 18:00

Pedro Cori · Accepted Answer · 2011-10-22 15:59:03Z

1

Like Claw said, the error probably means that your MyObject.new statement is returning a nil object for some reason. Then you're trying to call the function 'has_key' of that nil object.

Does your MyObject class throw an exception if you use .new! instead of .new ? If so, you could see why it's failing to return a proper MyObject object.

Edit

To catch an exception inside your 'new' method for the MyObject model, you could do something like:

def new
    begin
        #whatever is done in this method
    rescue => exception
        puts exception.message
    end
end

edited Oct 22, 2011 at 15:59

answered Oct 21, 2011 at 21:43

Pedro Cori

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4 Comments

namtax Over a year ago

Ok, when i try MyObject.new! I get :- NoMethodError: undefined method 'new!' for MyObject

Pedro Cori Over a year ago

Yeah. So there is no exception throwing .new method for your MyObject class. You could put a begin rescue statement inside the 'new' function in the model and see if it throws an exception (Look at edit in answer).

namtax Over a year ago

Hi Vota I actually abandoned my approach of storing the object in the array, so didnt get opportunity to try your solution. Its true that the error was occurring because the new statement was returning a nil object.

Pedro Cori Over a year ago

@namtax No worries. Glad I could be of some help :)

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