Calling functions without parentheses. When?

Hi there people!

I’m a newbie to both Rails & Ruby, I’ve just started reading the “Agile
Development with Rails” book yesterday.

I’ve noticed that in most of the times, we 're calling functions without
parentheses like *validates :title, presence: true *or assert
product.invalid? Sometimes though (mostly in views as I’ve noticed)
we’re
using parentheses, like <%= number_to_currency(product.price, unit:
“”).

*
*
My question: is this generally the preferred way to code in Rails? If
yes,
why? Sorry if this sounds silly but I can’t clearly see why we prefer
one
way over the other.

Also, I think it’s kinda hard to get used to the parentheses-less style,
cause everytime I see a line of code I must closely watch it’s syntax to
determine if this is a function call or something else. Is it only me?

Generally, I’m following the rule that every piece of code that has a
word
and then a space and then something else, for example *respond_to :blah,
blu: ‘test’ *is a function call, isn’t that right?

Thanks in advance.

On Jan 16, 2012, at 12:33 PM, Agis A. wrote:

Hi there people!

I’m a newbie to both Rails & Ruby, I’ve just started reading the “Agile
Development with Rails” book yesterday.

I’ve noticed that in most of the times, we 're calling functions without
parentheses like validates :title, presence: true or assert product.invalid?
Sometimes though (mostly in views as I’ve noticed) we’re using parentheses, like
<%= number_to_currency(product.price, unit: “”).

You’ll notice that when you do end up using the parentheses, it’s to
disambiguate nested function calls:

link_to ‘foo’, @bar, baz => ‘blarg’

vs

link_to ‘foo’, bar_path(bar), baz => ‘blarg’

or more elaborately

link_to( ‘foo’, bar_path(bar), baz => ‘blarg’ ) if bar

My question: is this generally the preferred way to code in Rails? If yes, why?
Sorry if this sounds silly but I can’t clearly see why we prefer one way over the
other.

Also, I think it’s kinda hard to get used to the parentheses-less style, cause
everytime I see a line of code I must closely watch it’s syntax to determine if
this is a function call or something else. Is it only me?

No, it’s not just you. Mostly, though, I find that it makes it difficult
to switch back and forth between Ruby and JavaScript, as I need to do
every day. I keep making newbie mistakes in JS like leaving the
parentheses out of if statements.

Generally, I’m following the rule that every piece of code that has a word and
then a space and then something else, for example respond_to :blah, blu: ‘test’ is
a function call, isn’t that right?

Seems like a good way to put it.

Walter

You cleared it for me, thank you. I don’t understand your code thought
:stuck_out_tongue:

On Jan 16, 2012, at 10:33 AM, Agis A. wrote:

My question: is this generally the preferred way to code in Rails? If yes, why?
Sorry if this sounds silly but I can’t clearly see why we prefer one way over the
other.

Being able to elide the parentheses is a “convenience”. But
unfortunately, sometimes then more complex calls don’t evaluate in the
right order, and require you to use parentheses to disambiguate, which
means you really can’t go completely without, so there’s only 2 styles
possible:

  • mixed, sometimes indicating function calls with parentheses and
    sometimes not
  • always use parentheses

I expect that when I put it like that, you’ll be able to guess my
preference :wink:


Scott R.
[email protected]
http://www.elevated-dev.com/
(303) 722-0567 voice

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