How can I append a single value to an array that is stored as an object of the class Citations?
class Citations
attr_accessor :paper,:arr
def dothing()
return paper.to_s.length
end
end
cit = Citations.new
#(1...5).each{ |x| cit.arr << x } # fails
cit.arr = [1,2,3,4] # works if I add the entire array as one unit
puts cit.arr
It fails because the array arr is not initialized. Change your class to this:
class Citations
attr_accessor :paper,:arr
def initialize
@arr = []
end
def dothing()
return paper.to_s.length
end
end
Naturally, your second attempt works fine because by using
cit.arr = [1,2,3,4]
You are in fact initializing it.
I can see a similar issue happening to paper (whatever it is).
In your code, this line: (1...5).each { |x| cit.arr << x } fails with error message:
undefined method `<<' for nil:NilClass (NoMethodError)
If you read the error message carefully, you will see that it indicates: cit.arr is nil because you did not initialize it and so when you call this: cit.arr << x, it's actually trying to call << method on the nil and fails because << method is not implemented on NilClass objects.
So, you need to initialize arr before calling cit.arr << x so that cit.arr is not nil.
You can do that in the initialize method of your class like this:
class Citations
attr_accessor :paper,:arr
def initialize
@arr = []
end
# rest of the codes
end
This will fix your problem.