Light copy edit to README

Author: kevinthecheung

FirebaseAuthUI/README.md

@@ -5,17 +5,18 @@ bindings on top of [Firebase](https://firebase.google.com) SDKs to eliminate
 boilerplate code and promote best practices.
 
 FirebaseUI provides a drop-in auth solution that handles the UI flows for
-signing in users with email addresses and passwords, Google Sign-In, and
-Facebook Login. It is built on top of [Firebase Auth](https://firebase.google.com/docs/auth).
+signing in users with email addresses and passwords, and federated identity
+providers such as Google Sign-In and Facebook Login. It is built on top of
+[Firebase Auth](https://firebase.google.com/docs/auth).
 
 The FirebaseUI Auth component implement best practices for authentication on
 mobile devices and websites, which can maximize sign-in and sign-up conversion
 for your app. It also handles edge cases like account recovery and account
 linking that can be security sensitive and error-prone to handle correctly.
 
 FirebaseUI can be easily customized to fit in with the rest of your app's visual
- style, and it is open source, so you aren't constrained in realizing the user
- experience you want.
+style, and it is open source, so you aren't constrained in realizing the user
+experience you want.
 
 Compatible FirebaseUI clients are also available for [Android](https://github.com/firebase/firebaseui-android/tree/master/auth)
 and [Web](https://github.com/firebase/firebaseui-web/).
@@ -52,7 +53,7 @@ instance. The `FUIAuth` instance associated with the default `FIRAuth`
 instance can be accessed as follows:
 
 ```swift
-// swift
+// Swift
 import Firebase
 import FirebaseAuthUI
 
@@ -65,7 +66,7 @@ authUI?.delegate = self
 ```
 
 ```objective-c
-// objc
+// Objective-C
 @import Firebase;
 @import FirebaseAuthUI;
 ...
@@ -78,7 +79,7 @@ authUI.delegate = self;
 This instance can then be configured with the providers you wish to support:
 
 ```swift
-// swift
+// Swift
 import FirebaseGoogleAuthUI
 import FirebaseFacebookAuthUI
 import FirebaseTwitterAuthUI
@@ -92,7 +93,7 @@ self.authUI?.providers = providers
 ```
 
 ```objective-c
-// objc
+// Objective-C
 @import FirebaseGoogleAuthUI;
 @import FirebaseFacebookAuthUI;
 @import FirebaseTwitterAuthUI;
@@ -105,18 +106,18 @@ NSArray<id<FUIAuthProvider>> *providers = @[
 _authUI.providers = providers;
 ```
 
-For Google sign in support, add custom URL schemes to your Xcode project
+For Google Sign-in support, add custom URL schemes to your Xcode project
 (step 1 of the [implement Google Sign-In documentation](https://developers.google.com/firebase/docs/auth/ios/google-signin#2_implement_google_sign-in)).
 
-For Facebook sign in support, follow step 3 and 4 of
-[Facebook login documentation](https://developers.google.com/firebase/docs/auth/ios/facebook-login#before_you_begin)
-, and add custom URL schemes following step 5 of [Facebook SDK for iOS-Getting started documentation](https://developers.facebook.com/docs/ios/getting-started).
+For Facebook Login support, follow step 3 and 4 of
+[Facebook login documentation](https://developers.google.com/firebase/docs/auth/ios/facebook-login#before_you_begin),
+and add custom URL schemes following step 5 of [Facebook SDK for iOS-Getting started documentation](https://developers.facebook.com/docs/ios/getting-started).
 
-Finally add a call to handle the URL that your application receives at the end of the
-Google/Facebook authentication process.
+Finally, add a call to handle the URL that your application receives at the end
+of the Google/Facebook authentication process.
 
 ```swift
-// swift
+// Swift
 func application(_ app: UIApplication, open url: URL, options: [UIApplicationOpenURLOptionsKey : Any]) -> Bool {
   let sourceApplication = options[UIApplicationOpenURLOptionsKey.sourceApplication] as! String?
   if FUIAuth.defaultAuthUI()?.handleOpen(url, sourceApplication: sourceApplication) ?? false {
@@ -128,7 +129,7 @@ func application(_ app: UIApplication, open url: URL, options: [UIApplicationOpe
 ```
 
 ```objective-c
-// objc
+// Objective-C
 - (BOOL)application:(UIApplication *)app openURL:(NSURL *)url options:(NSDictionary *)options {
   NSString *sourceApplication = options[UIApplicationOpenURLOptionsSourceApplicationKey];
   return [[FUIAuth defaultAuthUI] handleOpenURL:url sourceApplication:sourceApplication];
@@ -144,7 +145,7 @@ app or present it from another view controller within your app.  In order to
 present the `authViewController` obtain as instance as follows:
 
 ```swift
-// swift
+// Swift
 
 // Present the auth view controller and then implement the sign in callback.
 let authViewController = authUI!.authViewController()
@@ -155,7 +156,7 @@ func authUI(_ authUI: FUIAuth, didSignInWith user: FIRUser?, error: Error?) {
 ```
 
 ```objective-c
-// objc
+// Objective-C
 UINavigationController *authViewController = [authUI authViewController];
 // Use authViewController as your root view controller,
 // or present it on top of an existing view controller.
@@ -166,36 +167,36 @@ UINavigationController *authViewController = [authUI authViewController];
 ```
 
 ## Customizing FirebaseUI for authentication
-### Terms of Service (ToS) URL customization:
+### Custom terms of Service (ToS) URL
 
 The Terms of Service URL for your application, which is displayed on the
 email/password account creation screen, can be specified as follows:
 
 ```swift
-// swift
+// Swift
 let kFirebaseTermsOfService = URL(string: "https://firebase.google.com/terms/")!
 authUI?.tosurl = kFirebaseTermsOfService
 ```
 
 ```objective-c
-// objc
+// Objective-C
 authUI.TOSURL = [NSURL URLWithString:@"https://example.com/tos"];
 ```
 
 ### Custom strings
 
 You can override the default messages and prompts shown to your users. This can
-be useful for things such as adding support for other languages besides English.
+be useful for things such as adding support for languages other than English.
 
 In order to do so:
 
 ```swift
-// swift
+// Swift
 authUI?.customStringsBundle = NSBundle.mainBundle() // Or any custom bundle.
 ```
 
 ```objective-c
-// objc
+// Objective-C
 authUI.customStringsBundle = [NSBundle mainBundle]; // Or any custom bundle.
 ```
 
@@ -215,34 +216,35 @@ subclass by implementing the delegate method
 `authPickerViewControllerForAuthUI:` as follows:
 
 ```swift
-// swift
+// Swift
 func authPickerViewController(for authUI: FUIAuth) -> FUIAuthPickerViewController {
   return CustomAuthPickerViewController(authUI: authUI)
 }
 ```
 
 ```objective-c
-// objc
+// Objective-C
 - (FUIAuthPickerViewController *)authPickerViewControllerForAuthUI:(FUIAuth *)authUI {
   return [[CustomAuthPickerViewController alloc] initWithAuthUI:authUI];
 }
 ```
 
-### Custom Email Identity provider screens
+### Custom email/password screens
 
-You can entirely customize all email provider screens. Which includes but not limited to:
-- hide top `UINavigationBar`
-- add `Cancel` button
-- change type of controls (don't use `UITableView`)
+You can customize all email/password screens, including but not limited to:
+- Hiding the top `UINavigationBar`
+- Adding a `Cancel` button
+- Use a UI view other than `UITableView`
 Things that are not customizable:
-- `UIAlertController` popups (you can't show error label instead of alert controller)
-- modification of screen flow (you can't combine screens, skip particular screens)
-- disabling validation (e g email validation)
+- `UIAlertController` popups (showing error labels instead)
+- Modifying the screen flow (combining screens or skipping particular screens)
+- Disabling validation, including email validation
 
-In order to achieve email provider screen customization, create subclass of appropriate controller and implement it to your needs. Provide `FUIAuth` with an instance of your
-subclass by implementing the delegate methods:
+To customize the email/password screens, create a subclass of appropriate
+controller and implement it to your needs. Then set up `FUIAuth` with an
+instance of your subclass by implementing the following delegate methods:
 ```swift
-// swift
+// Swift
 func emailEntryViewController(for authUI: FUIAuth) -> FUIEmailEntryViewController {
   return CustomEmailEntryViewController(authUI: authUI)
 }
@@ -262,11 +264,10 @@ func passwordRecoveryViewController(for authUI: FUIAuth, email: String) -> FUIPa
 func passwordVerificationViewController(for authUI: FUIAuth, email: String, newCredential: FIRAuthCredential) -> FUIPasswordVerificationViewController {
   return CustomPasswordVerificationViewController(authUI: authUI, email: email, newCredential: newCredential)
 }
-
 ```
 
 ```objective-c
-// objc
+// Objective-C
 - (FUIEmailEntryViewController *)emailEntryViewControllerForAuthUI:(FUIAuth *)authUI {
   return [[CustomEmailEntryViewController alloc] initWithAuthUI:authUI];
 
@@ -290,7 +291,7 @@ func passwordVerificationViewController(for authUI: FUIAuth, email: String, newC
                                                                          email:(NSString *)email {
   return [[CustomPasswordRecoveryViewController alloc] initWithAuthUI:authUI
                                                                 email:email];
-  
+
 }
 
 - (FUIPasswordVerificationViewController *)passwordVerificationViewControllerForAuthUI:(FUIAuth *)authUI
@@ -302,10 +303,12 @@ func passwordVerificationViewController(for authUI: FUIAuth, email: String, newC
 }
 ```
 
-While customizing call original methods (see subclassed header). Most frequent but not limited are:
-- `- (void)onNext:(NSString *)textFieldValue;` // or any action which lead to the next screen
-- `- (void)didChangeTextField:(NSString *)textFieldValue;` // usually called in viewWillAppear and after modification of entry text field;
+In your custom view controllers, call the same FirebaseUI methods as their
+parent classes. For example:
+- `- (void)onNext:(NSString *)textFieldValue; // Or any action that leads to the next screen`
+- `- (void)didChangeTextField:(NSString *)textFieldValue; // Usually called in viewWillAppear and after modification of text entry field`
 - `- (void)onBack;`
 - `- (void)cancelAuthorization;`
 
-You can refer to objective-c and swift samples to see how customization can be achieved.
+Refer to the Objective-C and Swift samples for examples of how you can customize
+these views.