Feature #11167
closedAllow an attr_ variant for query-methods that end with a question mark '?' character, such as: def foo? returning @foo
Description
Hi guys,
Hi nobu :)
Also hi matz if matz reads this, and of course the rest of the core
team and everyone else.
Today on IRC, this mini-discussion happened (I show a snippet):
<apeiros> I really miss attr_query or whatever you want to name it
<apeiros> which would generate a ? method too
<jhass> apeiros: crystal has :P getter?
<apeiros> nice
Ok, so the language crystal has something ruby does not have.
We can't let those newcomers get away with making ruby look old
now can we!
I use ruby not crystal but I very often use methods that end
with a '?' query mark in ruby. It helps me in simple if clauses
such as:
if hash.has_key?
if hash.key?
if cat.is_hungry?
(In the latter, it might be a cat of class Cat
instance, with
an instance variable called @is_hungry
, and when the cat is
fed with food, it is not hungry logically.)
We can generate these @ivars
through attr_
* right now as is
already, such as:
attr_reader :foo
def foo; @foo; end
attr_writer :foo
def foo=(i); @foo = i; end
attr_accessor :foo
^^^ Combines the above two methods into one.
But we have no way to designate methods that end via '?'.
I do not know which API call would be nice. apeiros on
IRC suggested attr_query
I am fine with that. (The name is secondary for me, I
would like to have this feature available - what name
it would then have is not the main issue for me.)
apeiros then also suggested this syntax:
All attr_
* that would end with a ?
token, would be a
combination of attr_reader
and also a variant of the
above that has a '?' token, so for example:
attr_reader :foo?
Would create both a method foo()
and foo?()
.
People who do not need this, can continue to use:
attr_reader :foo
just fine.
So perhaps this suggestion is even better than
a new method (such as through attr_query()
)
(I also have added one more line from apeiros,
not sure if I understood it, but I think the
above explanation should suffice - here is the
other suggestion he did:)
apeiros> e.g. attr_reader :foo? -> foo? // attr_accessor :foo? -> foo= + foo? // all with @foo of course. and foo? returning true/false.
Ok, that's it.
Thanks for reading!
Updated by nobu (Nobuyoshi Nakada) over 9 years ago
- Is duplicate of Feature #10720: A proposal for something like: attr_reader :foo? - with the trailing '?' question mark added
Updated by matz (Yukihiro Matsumoto) over 9 years ago
Hi,
Is there any real-world use-case for the proposal?
It seems
def foo?
@foo
end
is just fine.
Matz.
Updated by djberg96 (Daniel Berger) over 9 years ago
Updated by spatulasnout (B Kelly) over 9 years ago
Hi Matz,
Yukihiro Matsumoto wrote:
Is there any real-world use-case for the proposal?
I've wanted this feature for years. :)
Here's an example from code I'm working with today:
def startup_complete?
@startup_complete
end
I would have preferred:
attr_reader :startup_complete?
It seems
def foo? @foo end
is just fine.
Perhaps fine, but clunky. :)
In other words, why do we ever use attr_reader
(etc.) at all?
We use attr_
.* because it's preferable to writing a bunch of
mini-functions.
The reasons are identical for the '?' variant.
Regards,
Bill
Updated by duerst (Martin Dürst) over 9 years ago
Daniel Berger wrote:
Abandoned all hope:
http://blade.nagaokaut.ac.jp/cgi-bin/scat.rb/ruby/ruby-core/5796
I think that this shows that there are several people who really like to use a foo? getter with a foo= setter. What it doesn't show that there are enough such people that it would balance out the confusion for those who think that a foo= setter goes together with a foo getter, at least by default.
With the current state, the main case is covered, nobody gets confused, and those who want a foo?/foo= pair can easily get it either as Matz showed above (easily reduced to one line) or by redefining the attr_... methods; the later is also very easy as it is usually about the first example given when explaining metaprogramming.
Updated by matz (Yukihiro Matsumoto) over 8 years ago
- Status changed from Open to Rejected
See #12046.
Matz.
Updated by mame (Yusuke Endoh) over 5 years ago
- Related to Feature #12046: Allow attr_reader :foo? to define instance method foo? for accessing @foo added
Updated by anders (Anders Bälter) almost 5 years ago
Like that!
sudo (Sudo Nice) wrote:
How about implementing it similarly to Crystal?
attr_accessor? :foo