UIKonf 2015: iOS API Design

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Transcript

1. share your code
2. share your code
3. Brian Gesiak
 @modocache
6. github.com/Quick/Quick/ issues/300
10. ✨ BananaUIKit
11. Series A
 B

12. Series X
 Y
 Z

13. abstractions 
 for what will change
16. @interface BananaAlertView : UIAlertView + (void)showWithTitleText:(NSString *)titleText messageText:(NSString *)messageText dismissButtonText:(NSString *)dismissButtonText; @end
18. @interface BananaAlertView : UIAlertView + (void)showWithTitleText:(NSString *)titleText messageText:(NSString *)messageText dismissButtonText:(NSString *)dismissButtonText; @end
19. @interface BananaAlertView : UIAlertView + (void)showWithTitleText:(NSString *)titleText messageText:(NSString *)messageText dismissButtonText:(NSString *)dismissButtonText; @end tintColor:(UIColor *)tintColor;
20. [BananaAlertView showWithTitleText:@"403 Error" messageText:@"Forbidden banana." dismissButtonText:@"Dang."];
21. [BananaAlertView showWithTitleText:@"403 Error" messageText:@"Forbidden banana." dismissButtonText:@"Dang."]; No known class method for selector 'showWithTitleText:messageText:…' 
22. BananaUIKit
23. BananaUIKit 2.0
25. v1.0 v1.1 v2.0 v2.1 v2.2
26. [BananaAlertView showWithTitleText:@"403 Error" messageText:@"Forbidden banana." dismissButtonText:@"Dang."]; No known class method for selector 'showWithTitleText:messageText:…' 
28. @interface BananaAlertView : UIAlertView + (void)showWithTitleText:(NSString *)titleText messageText:(NSString *)messageText dismissButtonText:(NSString *)dismissButtonText; + (void)showWithTitleText:(NSString *)titleText messageText:(NSString *)messageText dismissButtonText:(NSString *)dismissButtonText tintColor:(UIColor *)tintColor; @end
29. @interface BananaAlertView : UIAlertView + (void)showWithTitleText:(NSString *)titleText messageText:(NSString *)messageText dismissButtonText:(NSString *)dismissButtonText; + (void)showWithTitleText:(NSString *)titleText messageText:(NSString *)messageText dismissButtonText:(NSString *)dismissButtonText tintColor:(UIColor *)tintColor; @end
30. @implementation BananaAlertView + (void)showWithTitleText:(NSString *)titleText messageText:(NSString *)messageText dismissButtonText:(NSString *)dismissButtonText { [self showWithTitleText:titleText messageText:messageText dismissButtonText:dismissButtonText tintColor:[UIColor yellowColor]]; } + (void)showWithTitleText:(NSString *)titleText messageText:(NSString *)messageText dismissButtonText:(NSString *)dismissButtonText tintColor:(UIColor *)tintColor { // ... }
31. @implementation BananaAlertView + (void)showWithTitleText:(NSString *)titleText messageText:(NSString *)messageText dismissButtonText:(NSString *)dismissButtonText { [self showWithTitleText:titleText messageText:messageText dismissButtonText:dismissButtonText tintColor:[UIColor yellowColor]]; } + (void)showWithTitleText:(NSString *)titleText messageText:(NSString *)messageText dismissButtonText:(NSString *)dismissButtonText tintColor:(UIColor *)tintColor { // ... }
32. @implementation BananaAlertView + (void)showWithTitleText:(NSString *)titleText messageText:(NSString *)messageText dismissButtonText:(NSString *)dismissButtonText { [self showWithTitleText:titleText messageText:messageText dismissButtonText:dismissButtonText tintColor:[UIColor yellowColor]]; } + (void)showWithTitleText:(NSString *)titleText messageText:(NSString *)messageText dismissButtonText:(NSString *)dismissButtonText tintColor:(UIColor *)tintColor { // ... }
33. [BananaAlertView showWithTitleText:@"403 Error" messageText:@"Forbidden banana." dismissButtonText:@"Dang."];
34. [BananaAlertView showWithTitleText:@"403 Error" messageText:@"Forbidden banana." dismissButtonText:@"Dang."]; [BananaAlertView showWithTitleText:@"500 Error" messageText:@"Internal banana." dismissButtonText:@"Rats."
 tintColor:[UIColor redColor]];
35. public class BananaAlertView { public static func show( titleText: String, messageText: String, dismissButtonText: String) {
 // ... } }
36. public class BananaAlertView { public static func show( titleText: String, messageText: String, dismissButtonText: String) {
 // ... } } dismissButtonText: String, tintColor: UIColor = UIColor.yellowColor()) { // ... }
37. public typealias ButtonCallback = (buttonIndex: Int) -> () public class BananaAlertView { public static func show( titleText: String, messageText: String, dismissButtonText: String, dismissButtonCallback: ButtonCallback, tintColor: UIColor = UIColor.yellowColor()) { // ... } }
38. public typealias ButtonCallback = (buttonIndex: Int) -> () public class BananaAlertView { public static func show( titleText: String, messageText: String, dismissButtonText: String, dismissButtonCallback: ButtonCallback, tintColor: UIColor = UIColor.yellowColor()) { // ... } }
39. public typealias ButtonCallback = (buttonIndex: Int) -> () public class BananaAlertView { public static func show( titleText: String, messageText: String, dismissButtonText: String, dismissButtonCallback: ButtonCallback, tintColor: UIColor = UIColor.yellowColor()) { // ... } }
40. BananaAlertView.show( "500 Error", messageText: "Internal banana error.", dismissButtonText: "Rats.", dismissButtonCallback: { (buttonIndex: Int) in
 // ...
 }, tintColor: UIColor.redColor() )
41. BananaAlertView.show( "500 Error", messageText: "Internal banana error.", dismissButtonText: "Rats.", dismissButtonCallback: { (buttonIndex: Int) in
 // ...
 }, tintColor: UIColor.redColor() )
43. public typealias ButtonCallback = (buttonIndex: Int) -> () public class BananaAlertView { public static func show( titleText: String, messageText: String, dismissButtonText: String, dismissButtonCallback: ButtonCallback, tintColor: UIColor = UIColor.yellowColor()) { // ... } }
44. public typealias ButtonCallback = (buttonIndex: Int) -> () public class BananaAlertView { public static func show( titleText: String, messageText: String, dismissButtonText: String, dismissButtonCallback: ButtonCallback, tintColor: UIColor = UIColor.yellowColor()) { // ... } } (buttonIndex: Int, buttonTitle: String) -> ()
45. BananaAlertView.show( "500 Error", messageText: "Internal banana error.", dismissButtonText: "Rats.", dismissButtonCallback: { (buttonIndex: Int) in
 // ...
 }, tintColor: UIColor.redColor() )
46. BananaAlertView.show( "500 Error", messageText: "Internal banana error.", dismissButtonText: "Rats.", dismissButtonCallback: { (buttonIndex: Int) in
 // ...
 }, tintColor: UIColor.redColor() ) Cannot invoke 'show' with an argument list of type '(String, message… 
47. BananaAlertView.show( "500 Error", messageText: "Internal banana error.", dismissButtonText: "Rats.", dismissButtonCallback: { (buttonIndex: Int) in
 // ...
 }, tintColor: UIColor.redColor() ) Cannot invoke 'show' with an argument list of type '(String, message… 
48. parameter objects
49. public struct ButtonCallbackParameters { let buttonIndex: Int let buttonText: String } public typealias ButtonCallback = (buttonIndex: Int) -> ()
50. public struct ButtonCallbackParameters { let buttonIndex: Int let buttonText: String } public typealias ButtonCallback = (buttonIndex: Int) -> ()
51. public struct ButtonCallbackParameters { let buttonIndex: Int let buttonText: String } public typealias ButtonCallback = (buttonIndex: Int) -> () public typealias ButtonCallback = (parameters: ButtonCallbackParameters) -> ()
52. BananaAlertView.show( "500 Error", messageText: "Internal banana error.", dismissButtonText: "Rats.", dismissButtonCallback: { (buttonIndex: Int) in
 // ...
 }, tintColor: UIColor.redColor() )
53. BananaAlertView.show( "500 Error", messageText: "Internal banana error.", dismissButtonText: "Rats.", dismissButtonCallback: { (buttonIndex: Int) in
 // ...
 }, tintColor: UIColor.redColor() ) dismissButtonCallback: { parameters in if parameters.buttonText == "Rats." { // ... } },
54. BananaAlertView.show( "500 Error", messageText: "Internal banana error.", dismissButtonText: "Rats.", dismissButtonCallback: { (buttonIndex: Int) in
 // ...
 }, tintColor: UIColor.redColor() ) dismissButtonCallback: { parameters in if parameters.buttonText == "Rats." { // ... } },
55. public struct ButtonCallbackParameters { let buttonIndex: Int let buttonTitle: String } public typealias ButtonCallback = (parameters: ButtonCallbackParameters) -> ()
56. public struct ButtonCallbackParameters { let buttonIndex: Int let buttonTitle: String } public typealias ButtonCallback = (parameters: ButtonCallbackParameters) -> () let totalButtonCount: Int
57. public struct ButtonCallbackParameters { let buttonIndex: Int let buttonTitle: String } public typealias ButtonCallback = (parameters: ButtonCallbackParameters) -> () let totalButtonCount: Int
58. BananaAlertView.show( "500 Error", messageText: "Internal banana error.", dismissButtonText: "Rats.", dismissButtonCallback: { parameters in if parameters.buttonText == "Rats." { // ... } }, tintColor: UIColor.redColor() )
59. BananaAlertView.show( "500 Error", messageText: "Internal banana error.", dismissButtonText: "Rats.", dismissButtonCallback: { parameters in if parameters.buttonText == "Rats." { // ... } }, tintColor: UIColor.redColor() )
61. public struct ButtonCallbackParameters { let buttonIndex: Int
 let buttonTitle: String
 let totalButtonCount: Int } public typealias ButtonCallback = (parameters: ButtonCallbackParameters) -> ()
62. public struct ButtonCallbackParameters { let buttonIndex: Int
 let buttonTitle: String
 let totalButtonCount: Int } public typealias ButtonCallback = (parameters: ButtonCallbackParameters) -> () @availability(*, deprecated=2.0)
63. BananaAlertView.show( "500 Error", messageText: "Internal banana error.", dismissButtonText: "Rats.", dismissButtonCallback: { parameters in if parameters.buttonText == "Rats." { // ... } }, tintColor: UIColor.redColor() )
64. BananaAlertView.show( "500 Error", messageText: "Internal banana error.", dismissButtonText: "Rats.", dismissButtonCallback: { parameters in if parameters.buttonText == "Rats." { // ... } }, tintColor: UIColor.redColor() ) 'buttonText' was deprecated in * version 2.0 
65. public struct AlertViewOptions {
 public let dismissButtonText: String
 public let tintColor: UIColor public let animationDuration: NSTimeInterval } public class BananaAlertView { public static func show( titleText: String, messageText: String, options: AlertViewOptions) { // ... } }
66. public struct AlertViewOptions {
 public let dismissButtonText: String
 public let tintColor: UIColor public let animationDuration: NSTimeInterval } public class BananaAlertView { public static func show( titleText: String, messageText: String, options: AlertViewOptions) { // ... } } = AlertViewOptions()) { = "OK" = UIColor.yellowColor() = 1
74. # U+1F645 KENT BECK
75. #
76. future-proof your API
77. more overhead
78. don’t force users to choose
81. @interface JVFloatLabeledTextField : UITextField @property (nonatomic, assign) CGFloat floatingLabelYPadding UI_APPEARANCE_SELECTOR; @property (nonatomic, strong) UIFont *floatingLabelFont UI_APPEARANCE_SELECTOR; @property (nonatomic, strong) UIColor *floatingLabelTextColor UI_APPEARANCE_SELECTOR; @end
82. @interface JVFloatLabeledTextField : UITextField @property (nonatomic, assign) CGFloat floatingLabelYPadding UI_APPEARANCE_SELECTOR; @property (nonatomic, strong) UIFont *floatingLabelFont UI_APPEARANCE_SELECTOR; @property (nonatomic, strong) UIColor *floatingLabelTextColor UI_APPEARANCE_SELECTOR; @end
83. CGRect frame = CGRectMake(0.f, 0.f, 100.f, 44.f); JVFloatLabeledTextField *textField = [[JVFloatLabeledTextField alloc] initWithFrame:frame];
84. CGRect frame = CGRectMake(0.f, 0.f, 100.f, 44.f); JVFloatLabeledTextField *textField = [[JVFloatLabeledTextField alloc] initWithFrame:frame]; textField.placeholder = @"Price"; textField.floatingLabelYPadding = 10.f; textField.floatingLabelTextColor = [UIColor blueColor];
85. CGRect frame = CGRectMake(0.f, 0.f, 100.f, 44.f); JVFloatLabeledTextField *textField = [[JVFloatLabeledTextField alloc] initWithFrame:frame]; textField.placeholder = @"Price"; textField.floatingLabelYPadding = 10.f; textField.floatingLabelTextColor = [UIColor blueColor];
86. subclasses force people to use your class exclusively
89. @interface UITextField (JVFloatLabeledTextField) @property (nonatomic, assign) CGFloat floatingLabelYPadding UI_APPEARANCE_SELECTOR; @property (nonatomic, strong) UIFont *floatingLabelFont UI_APPEARANCE_SELECTOR; @property (nonatomic, strong) UIColor *floatingLabelTextColor UI_APPEARANCE_SELECTOR; @end @interface JVFloatLabeledTextField : UITextField
90. @interface UITextField (JVFloatLabeledTextField) @property (nonatomic, assign) CGFloat floatingLabelYPadding UI_APPEARANCE_SELECTOR; @property (nonatomic, strong) UIFont *floatingLabelFont UI_APPEARANCE_SELECTOR; @property (nonatomic, strong) UIColor *floatingLabelTextColor UI_APPEARANCE_SELECTOR; @end
91. @interface UITextField (JVFloatLabeledTextField) @property (nonatomic, assign) CGFloat floatingLabelYPadding UI_APPEARANCE_SELECTOR; @property (nonatomic, strong) UIFont *floatingLabelFont UI_APPEARANCE_SELECTOR; @property (nonatomic, strong) UIColor *floatingLabelTextColor UI_APPEARANCE_SELECTOR; @end
92. @interface UITextField (JVFloatLabeledTextField) { CGFloat _floatingLabelYPadding; } @property (nonatomic, assign) CGFloat floatingLabelYPadding UI_APPEARANCE_SELECTOR; @end
93. @interface UITextField (JVFloatLabeledTextField) { CGFloat _floatingLabelYPadding; } @property (nonatomic, assign) CGFloat floatingLabelYPadding UI_APPEARANCE_SELECTOR; @end
94. const void * const YPaddingKey = &YPaddingKey; - (void)setFloatingLabelYPadding:(CGFloat)yPadding { objc_setAssociatedObject( self, YPaddingKey, @(yPadding), OBJC_ASSOCIATION_RETAIN_NONATOMIC ); } - (CGFloat)floatingLabelYPadding { return [objc_getAssociatedObject(self, YPaddingKey) floatValue]; }
95. const void * const YPaddingKey = &YPaddingKey; - (void)setFloatingLabelYPadding:(CGFloat)yPadding { objc_setAssociatedObject( self, YPaddingKey, @(yPadding), OBJC_ASSOCIATION_RETAIN_NONATOMIC ); } - (CGFloat)floatingLabelYPadding { return [objc_getAssociatedObject(self, YPaddingKey) floatValue]; }
96. const void * const YPaddingKey = &YPaddingKey; - (void)setFloatingLabelYPadding:(CGFloat)yPadding { objc_setAssociatedObject( self, YPaddingKey, @(yPadding), OBJC_ASSOCIATION_RETAIN_NONATOMIC ); } - (CGFloat)floatingLabelYPadding { return [objc_getAssociatedObject(self, YPaddingKey) floatValue]; }
97. @interface UITextField (JVFloatLabeledTextField) @property (nonatomic, assign) CGFloat floatingLabelYPadding UI_APPEARANCE_SELECTOR; @property (nonatomic, strong) UIFont *floatingLabelFont UI_APPEARANCE_SELECTOR; @property (nonatomic, strong) UIColor *floatingLabelTextColor UI_APPEARANCE_SELECTOR; @end
98. @interface UITextField (JVFloatLabeledTextField) @property (nonatomic, assign) CGFloat floatingLabelYPadding UI_APPEARANCE_SELECTOR; @property (nonatomic, strong) UIFont *floatingLabelFont UI_APPEARANCE_SELECTOR; @property (nonatomic, strong) UIColor *floatingLabelTextColor UI_APPEARANCE_SELECTOR; @end
99. const void * const YPaddingKey = &YPaddingKey; const void * const FontKey = &FontKey; const void * const TextColorKey = &TextColorKey; - (void)setFloatingLabelYPadding:(CGFloat)yPadding { objc_setAssociatedObject( self, YPaddingKey, @(yPadding), OBJC_ASSOCIATION_RETAIN_NONATOMIC ); } - (CGFloat)floatingLabelYPadding { return [objc_getAssociatedObject(self, YPaddingKey) floatValue];
100. } - (UIFont *)floatingLabelFont { return objc_getAssociatedObject(self, FontKey); } - (void)setFloatingLabelTextColor:(UIColor *)color { objc_setAssociatedObject( self, TextColorKey, color, OBJC_ASSOCIATION_RETAIN_NONATOMIC ); } - (UIColor *)floatingLabelTextColor { return objc_getAssociatedObject(self, TextColorKey); }
101. extension UITextField { var floatingLabelYPadding: CGFloat { set { objc_setAssociatedObject( self, &YPaddingKey, newValue, objc_AssociationPolicy(OBJC_ASSOCIATION_ASSIGN) ) } get { if let padding = objc_getAssociatedObject( self, &YPaddingKey) as? CGFloat { return padding } else { return 0
102. extension UITextField { var floatingLabelYPadding: CGFloat { set { objc_setAssociatedObject( self, &YPaddingKey, newValue, objc_AssociationPolicy(OBJC_ASSOCIATION_ASSIGN) ) } get { if let padding = objc_getAssociatedObject( self, &YPaddingKey) as? CGFloat { return padding } else { return 0
103. &TextColorKey, newValue, objc_AssociationPolicy( OBJC_ASSOCIATION_RETAIN_NONATOMIC) ) } get { if let color = objc_getAssociatedObject( self, &TextColorKey) as? UIColor { return color } else { return UIColor.blackColor() } } } }
104. doesn’t scale
105. // objc4-532/runtime/objc-references.mm
 
 // class AssociationsManager manages a lock / hash table // singleton pair. Allocating an instance acquires the // lock, and calling its assocations() method // lazily allocates it. class AssociationsManager { static OSSpinLock _lock; // associative references: // object pointer -> PtrPtrHashMap. static AssociationsHashMap *_map; public: AssociationsManager() { OSSpinLockLock(&_lock); } ~AssociationsManager() { OSSpinLockUnlock(&_lock); } };
106. CGFloat *floatingLabelYPadding UIFont *floatingLabelFont UIColor *floatingLabelTextColor UIColor *floatingLabelActiveColor BOOL animateEvenIfNotFirstResponder UITextField
 (JVFloatLabeledTextField)
107. CGFloat *floatingLabelYPadding UIFont *floatingLabelFont UIColor *floatingLabelTextColor UIColor *floatingLabelActiveColor BOOL animateEvenIfNotFirstResponder JVFloatLabeledOptions
108. CGFloat *floatingLabelYPadding UIFont *floatingLabelFont UIColor *floatingLabelTextColor UIColor *floatingLabelActiveColor BOOL animateEvenIfNotFirstResponder JVFloatLabeledOptions UITextField
 (JVFloatLabeledTextField) JVFloatLabeledOptions *options
109. extension UITextField { var options: FloatLabelOptions { get { if let options = objc_getAssociatedObject( self, &OptionsKey) as? FloatLabelOptions { return options } else { return FloatLabelOptions() } } set { // ... } } }
110. extension UITextField { var options: FloatLabelOptions { get { if let options = objc_getAssociatedObject( self, &OptionsKey) as? FloatLabelOptions { return options } else { return FloatLabelOptions() } } set { // ... } } }
111. extension UITextField { var options: FloatLabelOptions { get { if let options = objc_getAssociatedObject( self, &OptionsKey) as? FloatLabelOptions { return options } else { return FloatLabelOptions() } } set { // ... } } }
112. extension UITextField { var options: FloatLabelOptions { get { if let options = objc_getAssociatedObject( self, &OptionsKey) as? FloatLabelOptions { return options } else { return FloatLabelOptions() } } set { // ... } } }
113. @objc class FloatLabelOptions { let yPadding: CGFloat let font: UIFont let textColor: UIColor // ... }
114. @objc class FloatLabelOptions { let yPadding: CGFloat let font: UIFont let textColor: UIColor // ... }
115. #
116. compose multiple categories
117. runtime sorcery
120. let options = MDCSwipeOptions() options.threshold = 130 options.onPan = { state in switch state.direction { case .Left: self.bookmarkView.alpha = 0 self.dontBookmarkView.alpha = state.thresholdRatio case .Right: self.bookmarkView.alpha = state.thresholdRatio self.dontBookmarkView.alpha = 0 } } webView.mdc_swipeToChooseSetup(options)
121. let options = MDCSwipeOptions() options.threshold = 130 options.onPan = { state in switch state.direction { case .Left: self.bookmarkView.alpha = 0 self.dontBookmarkView.alpha = state.thresholdRatio case .Right: self.bookmarkView.alpha = state.thresholdRatio self.dontBookmarkView.alpha = 0 } } webView.mdc_swipeToChooseSetup(options)
122. let options = MDCSwipeOptions() options.threshold = 130 options.onPan = { state in switch state.direction { case .Left: self.bookmarkView.alpha = 0 self.dontBookmarkView.alpha = state.thresholdRatio case .Right: self.bookmarkView.alpha = state.thresholdRatio self.dontBookmarkView.alpha = 0 } } webView.mdc_swipeToChooseSetup(options)
123. let options = MDCSwipeOptions() options.threshold = 130 options.onPan = { state in switch state.direction { case .Left: self.bookmarkView.alpha = 0 self.dontBookmarkView.alpha = state.thresholdRatio case .Right: self.bookmarkView.alpha = state.thresholdRatio self.dontBookmarkView.alpha = 0 } } webView.mdc_swipeToChooseSetup(options)
124. let options = MDCSwipeOptions() options.threshold = 130 options.onPan = { state in switch state.direction { case .Left: self.bookmarkView.alpha = 0 self.dontBookmarkView.alpha = state.thresholdRatio case .Right: self.bookmarkView.alpha = state.thresholdRatio self.dontBookmarkView.alpha = 0 } } webView.mdc_swipeToChooseSetup(options)
125. let options = MDCSwipeOptions() options.threshold = 130 options.onPan = { state in switch state.direction { case .Left: self.bookmarkView.alpha = 0 self.dontBookmarkView.alpha = state.thresholdRatio case .Right: self.bookmarkView.alpha = state.thresholdRatio self.dontBookmarkView.alpha = 0 } } webView.mdc_swipeToChooseSetup(options)
126. let options = MDCSwipeOptions() options.threshold = 130 options.onPan = { state in switch state.direction { case .Left: self.bookmarkView.alpha = 0 self.dontBookmarkView.alpha = state.thresholdRatio case .Right: self.bookmarkView.alpha = state.thresholdRatio self.dontBookmarkView.alpha = 0 } } webView.mdc_swipeToChooseSetup(options)
130. let options = MDCSwipeOptions() options.threshold = 130 options.onPan = { state in switch state.direction { case .Left: self.bookmarkView.alpha = 0 self.dontBookmarkView.alpha = state.thresholdRatio case .Right: self.bookmarkView.alpha = state.thresholdRatio self.dontBookmarkView.alpha = 0 } } webView.mdc_swipeToChooseSetup(options)
131. let options = MDCSwipeOptions() options.threshold = 130 options.onPan = { state in switch state.direction { case .Left: self.bookmarkView.alpha = 0 self.dontBookmarkView.alpha = state.thresholdRatio case .Right: self.bookmarkView.alpha = state.thresholdRatio self.dontBookmarkView.alpha = 0 } } webView.mdc_swipeToChooseSetup(options)
132. parameter objects
133. public struct ButtonCallbackParameters { let buttonIndex: Int
 let buttonTitle: String
 let totalButtonCount: Int } public typealias ButtonCallback = (parameters: ButtonCallbackParameters) -> ()
134. public struct ButtonCallbackParameters { let buttonIndex: Int
 let buttonTitle: String
 let totalButtonCount: Int } public typealias ButtonCallback = (parameters: ButtonCallbackParameters) -> () @availability(*, deprecated=2.0)
135. extensions vs. subclasses
136. extension UITextField { var options: FloatLabelOptions { get { // ... } set { // ... } } }
137. configuration objects
138. let options = MDCSwipeOptions() options.threshold = 130 options.onPan = { state in // ... } webView.mdc_swipeToChooseSetup(options)
139. prefer immutability
140. let options = MDCSwipeOptions() options.threshold = 130 options.onPan = { state in // ... } webView.mdc_swipeToChooseSetup(options)
141. - github.com/Quick/Quick
 - github.com/modocache/MDCSwipeToChoose 
 @modocache