Andrew Stewart
3/8/2007 11:57:00 AM
On 8 Mar 2007, at 11:40, Gregory Brown wrote:
> On 3/8/07, Andrew Stewart <boss@airbladesoftware.com> wrote:
>> Hello,
>>
>> I'm wondering how I can ask a variable what its name is, so that I
>> can convert it into a symbol.
>>
>> For example, I'd like to convert @bar to :bar.
>
> You can't. Variables aren't objects in Ruby. However, if you post a
> bit of context of the actual problem, I bet folks here will be able to
> help you solve it.
Aha! That explains why I couldn't. Here's the context:
I have a line item object in memory (@line_item) and a set of line
item attributes in a hash (keyed under params[:line_item]; this is in
a Rails controller). I only want to bother processing the line item
hash if the quantity of either the in-memory object or the one in the
hash is non-zero.
So I wrote this method:
# TODO: the only reason for passing the symbol is that I don't know
# how to convert the line_item's variable name into a symbol.
def line_item_relevant(line_item, symbol)
# Either we have an existing line item with non-zero quantity
(line_item && line_item.quantity > 0) ||
# Or we hearing about a line item with non-zero quantity
(params[symbol] && params[symbol][:quantity] > 0)
end
And I call it like this:
... if line_item_relevant @line_item_jacket, :line_item_jacket
And like this:
... if line_item_relevant @line_item_shirt, :line_item_shirt
Et cetera.
It would be less repetitive if I could ditch the symbol argument to
the method. Hence my original question.
Any ideas would be welcome!
> You *can* get the listing of variables though:
>>> @foo = 10
> => 10
>>> instance_variables
> => ["@foo"]
>>> a = 3
> => 3
>>> local_variables
> => ["_", "__", "a"]
That's useful to know, thanks.
Regards,
Andy Stewart