Update README.md

Author: hoc081098

README.md

@@ -10,6 +10,67 @@ Sample Mobile Validation using `rxdart` and `BLoC pattern`
 <img src="screenshots/demo.gif" height="480" alt="Cannot load image"/>
 </p>
 
+# BLoC
+### 1. Create stream controllers to receive input: email, password, submit
+```dart
+// Stream controllers
+final emailS = BehaviorSubject.seeded('');
+final passwordS = BehaviorSubject.seeded('');
+final isLoadingS = BehaviorSubject.seeded(false);
+final submitLoginS = PublishSubject<void>();
+final subjects = [emailS, passwordS, isLoadingS, submitLoginS];
+```
+### 2. Map email text and password text to set of errors
+```dart
+// Email error and password error stream
+final emailError$ = emailS.map(validator.validateEmail).distinct().share();
+ 
+final passwordError$ =
+    passwordS.map(validator.validatePassword).distinct().share();
+```
+### 3. Combine email errors stream and password errors stream to valid stream
+```dart
+// Submit stream
+final submit$ = submitLoginS
+    .throttleTime(const Duration(milliseconds: 500))
+    .withLatestFrom<bool, bool>(
+      Observable.combineLatest<Set<ValidationError>, bool>(
+        [emailError$, passwordError$],
+        (listOfSets) => listOfSets.every((errorsSet) => errorsSet.isEmpty),
+      ),
+      (_, isValid) => isValid,
+    )
+    .share();
+```
+### 4. Perform login effect based on submit stream
+```dart
+// Message stream
+final message$ = Observable.merge(
+  [
+    submit$
+        .where((isValid) => isValid)
+        .withLatestFrom2(
+          emailS,
+          passwordS,
+          (_, email, password) => Credential(
+            email: email,
+            password: password,
+          ),
+        )
+        .exhaustMap(
+          (credential) => interactor.performLogin(
+            credential,
+            isLoadingS,
+          ),
+        ),
+    submit$
+        .where((isValid) => !isValid)
+        .map((_) => const InvalidInformationMessage()),
+  ],
+).publish();
+```
+That's all :)
+
 ## Getting Started
 
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