BooksFragment.kt

override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        booksAdapter = BookAdapter(requireContext(), object : BookAdapter.ActionClickListener {
            override fun bookmark(book: BookWithStatus) {
                booksViewModel.bookmark(book)
            }

            override fun unbookmark(book: BookWithStatus) {
                booksViewModel.unbookmark(book)
            }
        })

        booksViewModel.getBooks("Robert C. Martin")
    }

override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
        super.onViewCreated(view, savedInstanceState)

        booksViewModel.books.observe(viewLifecycleOwner, {
            booksAdapter.submitUpdate(it)
        })

        booksViewModel.dataLoading.observe(viewLifecycleOwner, { loading ->
            when (loading) {
                true -> LayoutUtils.crossFade(pbLoading, rvBooks)
                false -> LayoutUtils.crossFade(rvBooks, pbLoading)
            }
        })

        rvBooks.apply {
            layoutManager =
                GridLayoutManager(requireContext(), COLUMNS_COUNT)
            adapter = booksAdapter
        }

        booksViewModel.error.observe(viewLifecycleOwner, {
            Toast.makeText(
                requireContext(),
                getString(R.string.an_error_has_occurred, it),
                Toast.LENGTH_SHORT
            ).show()
        })
    }