Assignment for has_many objects

Rails
1

Hello,

I’m playing with Agile Web dev for rails, inside which I encountered
this model :

class Order < ActiveRecord::Base
has_many :line_items
PAYMENT_TYPES = [
# Displayed stored in db
[ “Check” , “check” ],
[ “Credit card” , “cc” ],
[ “Purchase order” , “po” ]
]
# …
validates_presence_of :name, :address, :email, :pay_type
validates_inclusion_of :pay_type, :in => PAYMENT_TYPES.map {|disp,
value| value}

…

def add_line_items_from_cart(cart)
cart.items.each do |item|
li = LineItem.from_cart_item(item)
line_items << li
end
end
end

So far, I know that has_many adds several methods, such as line_items<<
and line_items=.
I also know that, inside a method, an assignment to some “var” without
“self.” before it might confuse ruby which can take “var” for a local
variable. So using self.var is “safer”.

But here, there’s no “self.line_items << li”. Why does calling
“line_items <<” is enough for this piece of code to understand that
line_items isn’t a mere variable ?

I know that there are some particular cases where “self.” isn’t
necessary. Maybe are we in one of them ?

Thanks

2

Arnaud J. wrote:

line_items isn’t a mere variable ?
“self” is not needed here because the line is not an assignment
(no “=”). Unlike an assignment, for the line to have any meaning
line_items must have been defined previously, so the interpreter
sees no ambiguity.

–
We develop, watch us RoR, in numbers too big to ignore.

3

Mark Reginald J. wrote:

“self” is not needed here because the line is not an assignment
(no “=”). Unlike an assignment, for the line to have any meaning
line_items must have been defined previously, so the interpreter
sees no ambiguity.

Got it. I’m not quite used to Ruby yet, that’s why. To me, calling
“some_array << 1” was like having an implicit “some_array = []”. But it
doesn’t work like that.

Thank you very much.