CocoaUI

Obtain and customize UIKit/Cocoa objects from SwiftUI components.

Demo

For example, Slider uses UISlider internally. Therefore, it can be customized by directly referencing the UISlider object as follows.

 Slider(value: $value)
    .cocoa { slider in // UISider
        slider.setThumbImage(.init(systemName: "swift"), for: .normal)
    }

Document

For components conforming to the protocol named DefaultCocoaViewBridging, you can get UIKit/Cocoa objects as follows. DefaultCocoaViewBridging gets the UIView object from SwiftUI.View. In contrast, DefaultCocoaControllerBridging gets the UIViewController object.
The CocoaBriding protocol defines a DefaultCocoaType.　　 For example, for Toggle, the DefaultCocoaType is UISwitch(iOS).　　 It can be handled as follows

 Toggle("Hello", isOn: .constant(true))
    .cocoa { `switch` in
        `switch`.onTintColor = .red
    }

Specify type

However, if the ToggleStyle is set to Button, UIButton is used internally instead of UISwitch. For such cases, it is also possible to retrieve the data by specifying the type as follows.

Toggle("Hello", isOn: .constant(true))
    .cocoa(for: UIButton.self) { button in
       button.layer.borderWidth = 1
    }

The method of specifying the type is defined in SwiftUI.View’s and does not need to conform to the DefaultCocoaViewBridging or DefaultCocoaControllerBridging protocols. If the specified type is not found, the closure will not be called.

Support additional component

extension XXView: DefaultCocoaViewBridging { // confirms `DefaultCocoaViewBridging`
    public typealias DefaultCocoaViewType = XXCocoaView // UIKit/Cocoa type
}

extension YYView: DefaultCocoaViewControllerBridging { // confirms `DefaultCocoaViewControllerBridging`
    public typealias DefaultCocoaControllerType = YYCocoaViewController // UIKit/Cocoa type
}

LifeCycle Event Modifiers

In some View lifecycle events, a modifier is provided to retrieve the obtained UIKit/Cocoa object. As an example, the following code hides the tabBar on push and redisplays it on pop.

TabView {
    NavigationView {
        List(0..<100) { i in
            NavigationLink {
                Text("Detail: \(i)")
                    .cocoa(for: CocoaViewController.self) { vc in
                        print(vc)
                    }
                    .onViewWillAppear { vc in
                        // Hide TabBar
                        vc?.tabBarController?.tabBar.isHidden = true
                    }
                    .onViewWillDisappear { vc in
                        // Show TabBar
                        vc?.tabBarController?.tabBar.isHidden = false
                    }
            } label: {
                Text("Row: \(i)")
            }
        }
    }
}

The following modifiers are available.

• onViewWillAppear
• onViewDidLoad
• onViewWillDisappear
• onViewDidDisAppear

SwiftUI and Cocoa correspondence table

This may vary depending on the operating system and usage conditions.

SwiftUI	style	UIKit(iOS)	Cocoa(macOS)	UIKit(tvOS)
ScrollView	-	UIScrollView	NSScrollView	UIScrollView
List	-	UICollectionView(>=iOS16) UITableView(<iOS16)	NSTableView	UITableView
Form	-	UICollectionView(>=iOS16) UITableView(<iOS16)	?	UITableView
TextField	-	UITextField	NSTextField	UITextField
SecureField	-	UITextField	NSTextField	UITextField
Slider	-	UISlider	NSSlider	-
Stepper	-	UIStepper	NSStepper	-
Picker	Wheel	UIPickerView	NSButton	-
	Inline	UIPickerView	?	UISegmentedControl
	Segmented	UISegmentedControl	NSSegmentedControl	UISegmentedControl
	Menu	?	NSButton	-
DatePicker	-	UIDatePicker	NSDatePicker	-
MultiDatePicker	-	UICalendarView	-	-
ColorPicker	-	UIColorWell	NSColorWell	-
Toggle	.switch	UISwitch	NSSwitch	-
	.button	UIButton	NSButton	-
	.checkbox	-	NSButton	-
TextEditor	-	UITextView	NSTextView	-
Button	-	-	NSButton	-
ProgressView	.linear	UIProgressView	NSProgressIndicator	UIProgressView
	.circular	UIActivityIndicatorView	NSProgressIndicator	UIActivityIndicatorView
TabView	-	UITabBarController	NSTabView	UITabBarController
NavigationView	DoubleColumn	UISplitViewController	NSSplitView	-
	Stack	UINavigationController	-	UINavigationController
NavigationStack	-	UINavigationController	?	UINavigationController
NavgationSplitView	-	UISplitViewController	NSSplitView	-