Ruby's attr_accessor vs setter method vs local variable

Asked Oct 07 '14 at 20:35

Active Oct 07 '14 at 21:22

Viewed 29 times

I have the following class defined

class MyClass
 attr_accessor :my_var
 def initialize
  @my_var = 0
 end

  def increment
    my_var = my_var + 1
  end
end

But if I run:

myObj = MyClass.new
puts myObj.increment # should output: 1

Ruby gives an error, although the expected output should be 1

ERROR MSG:

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

EDIT: The main question is, what is this line doing: my_var = my_var + 1

Is it invoking the setter method? Or is it trying to assign a local variable? In either case, why would it give the error msg it gives?

edited Oct 07 '14 at 21:22

asked Oct 07 '14 at 20:35

Sida Zhou

4

If you only call `inc`, not `incremenet`. :) – BroiSatse Oct 07 '14 at 20:36
Why would it show `1` *before* you increment? – tadman Oct 07 '14 at 20:40
4

What is the *error*? Also note that, trivially, `my_var = ..` is assigning to a *local variable* and *not* accessor; this has other repercussions as well. – user2864740 Oct 07 '14 at 20:40
You defined the method called `inc` but are trying to call the method called `increment`. – moonfly Oct 07 '14 at 20:43
1

`my_var = my_var + 1` should be `self.my_var = my_var + 1`. Otherwise, as @user2864740 says, you are only assigning a local variable `my_var`. – lurker Oct 07 '14 at 20:45
sry, inc was typo, now fixed to increment. – Sida Zhou Oct 07 '14 at 21:04
Pleas see my edit on the question... so, if it is trying to assign a local variable, then why does it give no method error? – Sida Zhou Oct 07 '14 at 21:10
Ok, now im reading the link :p – Sida Zhou Oct 07 '14 at 21:11

0 Answers0