«

Let's say I have this code:

class Mambo
attr_accesstor :safe
end

Now,

'safe', in my case, is a boolean. Problem is, the getter will be named
'safe', whereas I want it to be 'safe?'.

In other words, how do I make the getter 'safe?' and the setter 'safe'
?
--
Posted via http://www.ruby-forum.com/.

[Note: parts of this message were removed to make it a legal post.]

There's no built in way in ruby for it to know that you're going to put a
boolean in there. You'll need to do something like

class Mambo
attr_writer :safe

def safe?
!!@safe
end
end

HTH
Daniel

On 12 April 2010 11:00, Albert Schlef <> wrote:

> Let's say I have this code:
>
> class Mambo
> attr_accesstor :safe
> end
>
> Now,
>
> 'safe', in my case, is a boolean. Problem is, the getter will be named
> 'safe', whereas I want it to be 'safe?'.
>
> In other words, how do I make the getter 'safe?' and the setter 'safe'
> ?
> --
> Posted via http://www.ruby-forum.com/.
>
>

[Note: parts of this message were removed to make it a legal post.]

On 12 April 2010 11:10, Aaron Patterson <> wrote:

> On Mon, Apr 12, 2010 at 10:00:06AM +0900, Albert Schlef wrote:
> > Let's say I have this code:
> >
> > class Mambo
> > attr_accesstor :safe
> > end
> >
> > Now,
> >
> > 'safe', in my case, is a boolean. Problem is, the getter will be named
> > 'safe', whereas I want it to be 'safe?'.
> >
> > In other words, how do I make the getter 'safe?' and the setter 'safe'
> > ?
>
> In situations like this, I make two "getters" and leave the assignment
> alone. Other ruby programmers expect your "setters" to be in the form
> of "obj.safe = true", not "obj.safe(true)".
>
> Try something like this:
>
> class Mambo
> attr_accesstor :safe
> alias :safe? :safe
> end
>
> Here it is in action:
>
> irb(main):001:0> class Mambo
> irb(main):002:1> attr_accessor :safe
> irb(main):003:1> alias :safe? :safe
> irb(main):004:1> end
> => nil
> irb(main):005:0> m = Mambo.new
> => #<Mambo:0x000001010cab50>
> irb(main):006:0> m.safe = true
> => true
> irb(main):007:0> m.safe?
> => true
> irb(main):008:0>
>
> --
> Aaron Patterson
> http://tenderlovemaking.com/


Unfortunately this doesn't support safe? being boolean always. It could be
something other than true false (may not be a problem)

If you want to use attr_accessor rather than simply aliasing the method I'd
suggest

def safe?
!!safe
end

This way the expectation of a ? method to return a boolean is preserved.

Cheers
Daniel

Aaron Patterson wrote:
> alias :safe? :safe

Daniel wrote:
> def safe?
> !!@safe
> end


Thank you both. I wanted to make sure there's no built-in way to do
this.

(BTW, in Lisp (CLOS) it's possible to specify the getter/setter names.)
--
Posted via http://www.ruby-forum.com/.

Albert Schlef wrote:
> Thank you both. I wanted to make sure there's no built-in way to do
> this.

Hey, I've just discovered that 'ri' tells me that Module has an
'attr_reader?' method that creates a question-mark attribute.

Problem is, 'ri' displays methods from everything I've installed on my
system, so I can't know if 'attr_reader?' is provided by Ruby itself or
by some wacky gem.
--
Posted via http://www.ruby-forum.com/.

[Note: parts of this message were removed to make it a legal post.]

On Mon, Apr 12, 2010 at 12:35 AM, Albert Schlef <>wrote:

> Albert Schlef wrote:
> > Thank you both. I wanted to make sure there's no built-in way to do
> > this.
>
> Hey, I've just discovered that 'ri' tells me that Module has an
> 'attr_reader?' method that creates a question-mark attribute.
>
> Problem is, 'ri' displays methods from everything I've installed on my
> system, so I can't know if 'attr_reader?' is provided by Ruby itself or
> by some wacky gem.
> --
> Posted via http://www.ruby-forum.com/.
>
>
Doesn't work for me, so probably from some gem.

You could do something like this:

class Module
def attr_accessor?(*methods)
methods.each do |method|
ivar = "@#{method}"
define_method("#{method}=") { |value| instance_variable_set ivar ,
value }
define_method("#{method}?") { !!instance_variable_get(ivar) }
end
end
end


class Example
attr_accessor? :abc
end

e = Example.new
e.abc = true
e.abc? # => true

e.abc = false
e.abc? # => false

e.abc = 1
e.abc? # => true

e.abc = nil
e.abc? # => false

e.abc = :adsf
e.abc? # => true




There was also a ruby quiz about attr methods
http://rubyquiz.com/quiz67.html And there is a gem based off of it
http://github.com/ahoward/fattr

I don't know where yours came from, though.

On Apr 11, 9:13=A0pm, Daniel N <has....@gmail.com> wrote:

> Unfortunately this doesn't support safe? being boolean always. =A0It coul=
d be
> something other than true false (may not be a problem)
>
> If you want to use attr_accessor rather than simply aliasing the method I=
'd
> suggest
>
> def safe?
> =A0 !!safe
> end
>
> This way the expectation of a ? method to return a boolean is preserved.

I used to think this too, but... I think it was Austin Ziegler who
made the argument against using anything like "!!". In ruby it isn't
necessary. Anything that isn't nil or false is evaluated by
conditionals as true. I haven't once seen a case where it mattered if
a boolean was returned rather than the underlying value.

On Apr 11, 9:00=A0pm, Albert Schlef <albertsch...@gmail.com> wrote:
> Let's say I have this code:
>
> class Mambo
> =A0 attr_accesstor :safe
> end
>
> Now,
>
> 'safe', in my case, is a boolean. Problem is, the getter will be named
> 'safe', whereas I want it to be 'safe?'.

In Ruby 1.9, once can create writers with

attr =3D

I love this feature b/c it means I can just use #attr and not need the
other three attr_reader, attr_writer and attr_accessor.

It would be cool if we could make "boolean" readers too with,

attr ?

(P.S. Is the attr =3D feature going to get back ported to 1.8.8?)

On Apr 11, 7:00=A0pm, Albert Schlef <albertsch...@gmail.com> wrote:
> Let's say I have this code:
>
> class Mambo
> =A0 attr_accesstor :safe
> end
>
> Now,
>
> 'safe', in my case, is a boolean. Problem is, the getter will be named
> 'safe', whereas I want it to be 'safe?'.
>
> In other words, how do I make the getter 'safe?' and the setter 'safe'
> ?

Wouldn't that have been nice?

http://blade.nagaokaut.ac.jp/cgi-bin...ruby-core/5796

Regards,

Dan

Intransition wrote:
>>
>> This way the expectation of a ? method to return a boolean is preserved.
>
> I used to think this too, but... I think it was Austin Ziegler who
> made the argument against using anything like "!!". In ruby it isn't
> necessary. Anything that isn't nil or false is evaluated by
> conditionals as true. I haven't once seen a case where it mattered if
> a boolean was returned rather than the underlying value.

In a DRb situation, I'd rather send 'true' across the wire than
an arbitrary object.

Also, if the boolean value is going to be stored somewhere,
I'd rather store a 'true' than reference an arbitrary object.

Also, if I'm adding a temporary debug printout #{someval.inspect}
it's nicer to see true/false in the output.


Regards,

Bill