Using self.attribute for writing vs reading - confusion

Ruby
1

Lets take this simple example

class NewBook

attr_accessor :books

def initialize
@books = []
end

def some_method
books[0] #( the reader for books works fine and will recall the
class value @books, however)

  books = [4,5,6,7] # ( books will not actually get assigned here

unless I do self.books = [4,5,6,7] )
end

end

Why do you have to use self.books= on writer methods, but you can simply
put books on reader method.

Very confused. Any help would be great.

2

On Apr 12, 10:28 pm, Aryk G. [email protected] wrote:

def some_method
put books on reader method.

Very confused. Any help would be great.

–
Posted viahttp://www.ruby-forum.com/.

In the case of “books = foo”, ruby thinks books is a new locally
scoped variable. It’s a ruby language “gotcha”. To inform ruby that
you want to call the “book=” method on your object, you have to
explicitly mention the reciever: “self.book = foo”

OR, as long as you are in an instance method of that class, you can
just access the instance variable directly: “@book = foo”

3

On Apr 12, 2007, at 10:28 PM, Aryk G. wrote:

Why do you have to use self.books= on writer methods, but you can
simply
put books on reader method.

books = [1,2,3,4]
list = [5,6,7,8]

Which one is a setter method and which one is an assignment
to a local variable?

You have to use self.books so that the parser can
distinguish between a call to the setter method
and a local variable assignment. This is a side effect of
their being no need to declare local variables nor a sigil
for local variables (like @ and $ for instance and global
variables).

Gary W.