When restored data, watch has not been emitted

[tychio]

I have some data as follow:

{
  formData: {
    foo: 'bar'
  }
}

and then I watch the property foo:

way.watch('formData.foo', function (foo) {
  //my code...
});

The watch has not been emitted after loaded page.
I found that the watchAll could be emitted, but I only want to watch a specific property, what should I do?