Data Binding observables and Kotlin

observable-extension.txt

// with just a simple extension function for the Data Binding ObservableField
inline fun <R> ObservableField<R>.observe(crossinline callback: (R) -> Unit) {
    this.addOnPropertyChangedCallback(object : Observable.OnPropertyChangedCallback() {
        override fun onPropertyChanged(p0: Observable?, p1: Int) {
            callback(get())
        }
    })
}
...

// observing the change of data is simple, clean and readable.
 viewModel.user.observe {
     //TODO use whatever with the observed data
 }
 

Type mismatch required: R
found: R?

Just add !! after get() and it will work fine.