Adding view model tag extensions

Author: Lucas Sales

app/src/main/java/com/monstarlab/arch/extensions/ViewModelEx.kt

@@ -0,0 +1,60 @@
+// Package set to androidx.lifecycle so we can have access to package private methods
+
+package androidx.lifecycle
+
+import com.monstarlab.arch.extensions.UseCaseResult
+import com.monstarlab.arch.extensions.onError
+import com.monstarlab.core.sharedui.errorhandling.ViewError
+import com.monstarlab.core.sharedui.errorhandling.mapToViewError
+import kotlinx.coroutines.flow.*
+import kotlinx.coroutines.launch
+
+private const val ERROR_FLOW_KEY = "androidx.lifecycle.ErrorFlow"
+private const val LOADING_FLOW_KEY = "androidx.lifecycle.LoadingFlow"
+
+fun ViewModel.sendViewError(viewError: ViewError) {
+    viewModelScope.launch {
+        getErrorMutableSharedFlow().emit(viewError)
+    }
+}
+
+suspend fun ViewModel.emitViewError(viewError: ViewError) {
+    getErrorMutableSharedFlow().emit(viewError)
+}
+
+val ViewModel.viewErrorFlow: SharedFlow<ViewError>
+    get() {
+        return getErrorMutableSharedFlow()
+    }
+
+val ViewModel.loadingFlow: StateFlow<Boolean>
+    get() {
+        return getLoadingMutableStateFlow()
+    }
+
+
+private fun ViewModel.getLoadingMutableStateFlow(): MutableStateFlow<Boolean> {
+    val flow: MutableStateFlow<Boolean>? = getTag(LOADING_FLOW_KEY)
+    return flow ?: setTagIfAbsent(ERROR_FLOW_KEY, MutableStateFlow(false))
+}
+
+private fun ViewModel.getErrorMutableSharedFlow(): MutableSharedFlow<ViewError> {
+    val flow: MutableSharedFlow<ViewError>? = getTag(ERROR_FLOW_KEY)
+    return flow ?: setTagIfAbsent(ERROR_FLOW_KEY, MutableSharedFlow())
+}
+
+fun <T> Flow<T>.bindLoading(viewModel: ViewModel): Flow<T> {
+    return this
+            .onStart {
+                viewModel.getLoadingMutableStateFlow().value = true
+            }
+            .onCompletion {
+                viewModel.getLoadingMutableStateFlow().value = false
+            }
+}
+fun <T> Flow<UseCaseResult<T>>.bindError(viewModel: ViewModel): Flow<UseCaseResult<T>> {
+    return this
+            .onError {
+                viewModel.emitViewError(it.mapToViewError())
+            }
+}

app/src/main/java/com/monstarlab/features/login/LoginFragment.kt

@@ -3,7 +3,8 @@ package com.monstarlab.features.login
 import android.os.Bundle
 import android.view.View
 import androidx.lifecycle.lifecycleScope
-import androidx.lifecycle.viewModelScope
+import androidx.lifecycle.loadingFlow
+import androidx.lifecycle.viewErrorFlow
 import androidx.navigation.fragment.findNavController
 import androidx.transition.TransitionManager
 import com.google.android.material.snackbar.Snackbar
@@ -15,7 +16,6 @@ import com.monstarlab.arch.extensions.viewBinding
 import com.monstarlab.databinding.FragmentLoginBinding
 import kotlinx.coroutines.flow.launchIn
 import kotlinx.coroutines.flow.onEach
-import kotlinx.coroutines.launch
 
 class LoginFragment : BaseFragment(R.layout.fragment_login) {
 
@@ -36,7 +36,7 @@ class LoginFragment : BaseFragment(R.layout.fragment_login) {
             findNavController().navigate(R.id.resourceFragment)
         }
 
-        collectFlow(viewModel.errorFlow) { viewError ->
+        collectFlow(viewModel.viewErrorFlow) { viewError ->
             Snackbar.make(view, viewError.message, Snackbar.LENGTH_SHORT).show()
         }
 

app/src/main/java/com/monstarlab/features/login/LoginViewModel.kt

@@ -1,35 +1,28 @@
 package com.monstarlab.features.login
 
 import androidx.lifecycle.ViewModel
+import androidx.lifecycle.bindError
+import androidx.lifecycle.bindLoading
 import androidx.lifecycle.viewModelScope
-import com.monstarlab.arch.extensions.onError
 import com.monstarlab.arch.extensions.onSuccess
-import com.monstarlab.core.sharedui.errorhandling.ViewError
-import com.monstarlab.core.sharedui.errorhandling.mapToViewError
 import com.monstarlab.core.usecases.user.LoginUseCase
-import kotlinx.coroutines.flow.*
+import kotlinx.coroutines.flow.MutableSharedFlow
+import kotlinx.coroutines.flow.launchIn
 import javax.inject.Inject
 
 class LoginViewModel @Inject constructor(
         private val loginUseCase: LoginUseCase
-): ViewModel() {
-
-    val loadingFlow: MutableStateFlow<Boolean> = MutableStateFlow(false)
-    val errorFlow: MutableSharedFlow<ViewError> = MutableSharedFlow()
+) : ViewModel() {
     val loginResultFlow: MutableSharedFlow<Boolean> = MutableSharedFlow()
 
     fun login(email: String, password: String) {
         loginUseCase
                 .login(email, password)
-                .onStart {
-                    loadingFlow.value = true
-                }.onSuccess {
+                .bindLoading(this)
+                .bindError(this)
+                .onSuccess {
                     loginResultFlow.emit(true)
-                }.onError {
-                    errorFlow.emit(it.mapToViewError())
-                }.onCompletion {
-                    loadingFlow.value = false
-                }.launchIn(viewModelScope)
+                }
+                .launchIn(viewModelScope)
     }
-
 }