Casting of boolean values

[dmarkow]

Boolean values are stored as 0/1, and that's what CDQ returns when you query an object. Since ruby treats 0 as a truthy value, you can't do something like if person.happy, but instead have to do if person.happy == 1. I'm new to CDQ, so I'm not sure if this is something that should be cast to true/false automatically?

Sample schema:

schema "0001 initial" do
  entity "Person" do
    boolean :happy
  end
end

Sample REPL code:

(main)> p = Person.create(happy: false)
=> <Person: 0xb622490> (entity: Person; id: 0xb621a60 <x-coredata:///Person/tE660D344-00B6-4A86-A0BE-84A6EE30E7324> ; data: {
    happy = 0;
})
(main)> p.happy
=> 0
(main)> p.happy = true
=> true
(main)> p.happy
=> 1

[kemiller]

It's not trivial to do that because of the way core data works. You can't do it right in CDQManagedObject because CoreData will subclass your class and then add the property accessors rather than the other way around as in ActiveRecord. To work around that you can define question-mark predicate methods ("happy?"). To do it automatically you have to dig into Objective C, so I haven't got around to it.

[pixlwave]

Couldn't this be done with ruby's define_method? As long as you have a list of boolean properties (which we have in the schema), you could run something like this:

def self.define_predicate_methods

  bool_methods.each do |method|
    define_method("#{method}?") do
      self.send(method).boolValue
    end
  end

end

[pixlwave]

Just updating the snippet slightly, after realising that it didn't handle nil being returned. A better implementation would be:

def self.define_predicate_methods

  methods.each do |method|
    define_method("#{method}?") do
      value = self.send(method)
      value.nil? ? value : value.boolValue
    end
  end

end

[kemiller]

I'm don't remember why define_method didn't work for me, but if you can make it work, great. MotionData used Objective-C to get this feature, for what it's worth.