Hi Edward,
Context arguments in Objective-C are generally void pointers, which
makes them hard to use in Ruby. Also, since we run in Objective-C GC
mode, objects could potentially be collected since contexts do not set
up AFAIK write barriers.
I would recommend to set up an instance variable on your observer
instead (and pass nil as the context).
observer.instance_variable_set(:@context, your_context)
And later in your observer method, retrieve the ivar.
Laurent
On Apr 20, 2009, at 8:57 AM, Edward Hynes wrote:
I'd like to use contexts when registering some observers, but have
been unable to retrieve them, getting a "can't convert C/Objective-C
value `0x2822731' of type `v' to Ruby object" instead. The
following code, for example, will trigger the error
class Subject
attr_accessor :abc
end
class Observer
def observeValueForKeyPath keyPath, ofObject:object, change:change,
context:context
context[0]
end
end
subject = Subject.new
observer = Observer.new
subject.addObserver observer, forKeyPath:'abc', options:0,
context:'a context'
subject.setAbc 'some value'
Is there a way to retrieve an observation context? Or is there an
alternative way for observers to distinguish among multiple
registrations for a given object/keyPath?
Thanks,
Ed
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