+    enum class ViewModelBringer(var isDemo: Boolean) {

+        DEMO_VIEW_MODEL_BRINGER(true) {

+            override fun <T : ViewModel> getViewModel(fragment: Fragment, modelClass: Class<T>): T {

+                val name = modelClass.name

+                val mockName =

+                    "${name.substringBeforeLast(".")}.Mock${name.substringAfterLast(".")}"

+                try {

+                    val modelDemoClass = Class.forName(mockName) as Class<out T>

+                    return ViewModelProviders.of(fragment).get(modelDemoClass)

+                } catch (e: ClassNotFoundException) {

+                    return ViewModelProviders.of(fragment).get(modelClass)

+                }

+            }

+

+        },

+        VIEW_MODEL_BRINGER(false) {

+            override fun <T : ViewModel> getViewModel(fragment: Fragment, modelClass: Class<T>): T {

+                return ViewModelProviders.of(fragment).get(modelClass)

+            }

+        };

+

+        abstract fun <T : ViewModel> getViewModel(fragment: Fragment, modelClass: Class<T>): T

+    }

+

+    companion object {

+        fun <T : ViewModel> getViewModel(fragment: Fragment, modelClass: Class<T>): T {

+            return getInstance(BuildConfig.IS_DEMO).getViewModel(fragment, modelClass)

+        }

+

+        private fun getInstance(isDemo: Boolean): ViewModelBringer {

+            if (isDemo) return ViewModelBringer.DEMO_VIEW_MODEL_BRINGER

+            else return ViewModelBringer.VIEW_MODEL_BRINGER

+        }

+    }

+    ...

+    buildConfigField "boolean", "IS_DEMO", "true"

+    ...