Support for 'predicate' and 'clearer' methods

Activity

Sean O'Halpin
- State changed from new to resolved
As you have pointed out, #instance_variable_defined? and #remove_instance_variable do exactly what you want.

However, using them does rely on the underlying implementation of doodle, so I take your point. I really don't like the 'attribute query' methods of ActiveRecord (e.g. foo.name?) - IMHO they just add to the namespace clutter so I prefer two methods that take arguments over creating two more new methods per attribute.

Doodle already has #assigned?(name). I have just added #clear!(name), so that will be in the next release (real soon now). For example:
```
class Foo < Doodle
  has :name
end
foo = Foo("Jim")
foo.assigned?(:name) # => true
foo.clear!(:name)
foo.assigned?(:name) # => false
```
October 11th, 2009 @ 02:53 AM
Justin Ossevoort
The clearer is great, that really complements the <.assigned?>

I agree that the ActiveRecord way is ugly for it really conflicts with the way you'd expect boolean attributes to behave.
I was thinking more along the lines of:
```
class Foo < Doodle
  has :foo, :default => 'bar'
end

foo = Foo.new
foo.assigned?(:name) # => false
foo.has?(:name)      # => true

foo.foo = 'foobar'
foo.assigned?(:name) # => true
foo.has?(:name)      # => true
```
Where <.has?> nicely mirrors the declarative form of Doodle.
October 12th, 2009 @ 08:00 AM
Justin Ossevoort
- Tag set to feature
October 12th, 2009 @ 08:49 AM
Sean O'Halpin
I like #has?

obj.has?(name) would be syntactic sugar for
obj.doodle.attributes.key?(name) where obj can be either a class or an
instance.

I'll include this in the next release (so we'll have #has?, #assigned?
and #clear!).

While we're at it, can you think of any other reflections that should
be exposed at the class or instance level?

October 15th, 2009 @ 12:28 PM

I've been mulling over this for some days, but for these cover the really essential introspection needs. The only possibly relevant one that's possibly missing is whether or not something has a default value.

For this example I use valued? as the property, but I haven't given much thought for a name:

    require 'doodle'

    class Foo
        has simple_attr

        has default_attr do
            default{ 'bar' }
        end

        has init_attr do
            init{ 'bar' }
        end
    end

    f = Foo.new

    f.has?(:simple_attr)       # => true
    f.valued?(:init_attr)      # => false
    f.assigned?(:init_attr)    # => false

    f.has?(:default_attr)      # => true
    f.valued?(:default_attr)   # => true
    f.assigned?(:default_attr) # => false

    f.has?(:init_attr)         # => true
    f.valued?(:init_attr)      # => true
    f.assigned?(:init_attr)    # => true

The biggest problem with this one is that I haven't come up with a clear scenario for this information (though it clearly conveys information).

October 21st, 2009 @ 01:29 PM

Justin Ossevoort

oh and the first block should of course have read:

    f.has?(:simple_attr)       # => true
    f.valued?(:simple_attr)    # => false
    f.assigned?(:simple_attr)  # => false

Clear case of copy/past bug ;-)

October 21st, 2009 @ 01:34 PM

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