Simplify LoginTextField's placeholder code

- also makes it more reliable, previously it was only colored once and if changed it reverted to iOS default (which was happening for unknown reasons)

Author: nheagy

WordPressAuthenticator/NUX/WPWalkthroughTextField.h

@@ -6,7 +6,6 @@ IB_DESIGNABLE
 @property (nonatomic) IBInspectable BOOL showTopLineSeparator;
 @property (nonatomic) IBInspectable BOOL showSecureTextEntryToggle;
 @property (nonatomic) IBInspectable UIImage *leftViewImage;
-@property (nonatomic, strong) UIButton *secureTextEntryToggle;
 
 /// Width for the left view. Set to 0 to use the given frame in the view.
 /// Default is: 30
@@ -39,6 +38,5 @@ IB_DESIGNABLE
 @property (nonatomic) UIEdgeInsets contentInsets;
 
 - (instancetype)initWithLeftViewImage:(UIImage *)image;
-- (void)setupPlaceholder;
 
 @end

WordPressAuthenticator/NUX/WPWalkthroughTextField.m

@@ -8,6 +8,7 @@
 @import Gridicons;
 
 @interface WPWalkthroughTextField ()
+@property (nonatomic, strong) UIButton *secureTextEntryToggle;
 @property (nonatomic, strong) UIImage *secureTextEntryImageVisible;
 @property (nonatomic, strong) UIImage *secureTextEntryImageHidden;
 @end
@@ -85,13 +86,9 @@ - (void)commonInit
     self.showTopLineSeparator = NO;
     self.showSecureTextEntryToggle = NO;
 
-    [self setupPlaceholder];
-}
-
-- (void)setupPlaceholder
-{
     // Apply styles to the placeholder if one was set in IB.
     if (self.placeholder) {
+        // colors here are overridden in LoginTextField
         NSDictionary *attributes = @{
                                      NSForegroundColorAttributeName : WPStyleGuide.greyLighten10,
                                      NSFontAttributeName : self.font,
@@ -114,6 +111,7 @@ - (void)configureSecureTextEntryToggle {
 
     self.secureTextEntryToggle = [UIButton buttonWithType:UIButtonTypeCustom];
     self.secureTextEntryToggle.clipsToBounds = true;
+    // colors here are overridden in LoginTextField
     self.secureTextEntryToggle.tintColor = [WPStyleGuide greyLighten10];
     [self.secureTextEntryToggle addTarget:self action:@selector(secureTextEntryToggleAction:) forControlEvents:UIControlEventTouchUpInside];
 

WordPressAuthenticator/Signin/Login.storyboard

@@ -470,6 +470,7 @@
                                                         <rect key="frame" x="0.0" y="44" width="383" height="44"/>
                                                         <color key="backgroundColor" red="1" green="1" blue="1" alpha="1" colorSpace="custom" customColorSpace="sRGB"/>
                                                         <accessibility key="accessibilityConfiguration" identifier="passwordField"/>
+                                                        <nil key="textColor"/>
                                                         <fontDescription key="fontDescription" type="system" pointSize="14"/>
                                                         <textInputTraits key="textInputTraits" autocorrectionType="no" spellCheckingType="no" returnKeyType="next" enablesReturnKeyAutomatically="YES" secureTextEntry="YES" textContentType="one-time-code"/>
                                                         <userDefinedRuntimeAttributes>

WordPressAuthenticator/UI/LoginTextField.swift

@@ -3,14 +3,6 @@ import WordPressShared
 
 open class LoginTextField: WPWalkthroughTextField {
 
-    override open func awakeFromNib() {
-        super.awakeFromNib()
-        guard let secureTextEntryToggle = secureTextEntryToggle else {
-            return
-        }
-        secureTextEntryToggle.tintColor = WordPressAuthenticator.shared.style.placeholderColor
-    }
-
     override open func draw(_ rect: CGRect) {
         if showTopLineSeparator {
             guard let context = UIGraphicsGetCurrentContext() else {
@@ -22,16 +14,19 @@ open class LoginTextField: WPWalkthroughTextField {
         }
     }
 
-    override open func setupPlaceholder() {
-        guard let placeholder = placeholder,
-            let font = font else {
-            return
+    override open var placeholder: String? {
+        didSet {
+            guard let placeholder = placeholder,
+                let font = font else {
+                return
+            }
+
+            let attributes: [NSAttributedString.Key : Any] = [
+                .foregroundColor: WordPressAuthenticator.shared.style.placeholderColor,
+                .font: font
+            ]
+            attributedPlaceholder = NSAttributedString(string: placeholder, attributes: attributes)
         }
-        let attributes: [NSAttributedString.Key: Any] = [
-            .foregroundColor: WordPressAuthenticator.shared.style.placeholderColor,
-            .font: font
-        ]
-        self.attributedPlaceholder = NSAttributedString(string: placeholder, attributes: attributes)
     }
 
     override open var leftViewImage: UIImage! {