How to drag custom items in SwiftUI on macOS

Question

Created Jun ’20

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How can we drag views coupled to an NSItemProvider with a custom typeIdentifier or UTI ?
I know you can use the following methods in conjunction with predefined UTI types (like kUTTypeText etc.):

But what if I want to use an itemProvider with a custom UTI?
I tried:

Code Block swiftimport SwiftUI
struct ContentView: View {
	static let type = "com.devian.sampleapp.customstring.dragdroptype"
	@State var dropZoneIsHovered = false
	var body: some View {
		VStack {
			Text("Hello")
				.padding()
				.onDrag(createItem)
			Text("Dropzone")
				.padding()
				.background(dropZoneIsHovered ? Color.gray : nil)
				.onDrop(
					of: [ContentView.type],
					isTargeted: $dropZoneIsHovered,
					perform: acceptDrop(items:)
				)
		}.padding()
    }
	func createItem() -> NSItemProvider {
		NSItemProvider(
			item: "Hello" as NSString,
			typeIdentifier: ContentView.type
		)
	}
	func acceptDrop(items: [NSItemProvider]) -> Bool {
		print("Hurray we received a custom item")
		return true
	}
}

But the dropzone does not accept custom UTI's
I also tried to export the custom UTI using Info.plist:

Code Block xml<array>
	<dict>
		<key>UTTypeConformsTo</key>
		<array>
			<string>public.data</string>
		</array>
		<key>UTTypeIdentifier</key>
		<string>com.devian.sampleapp.customstring.dragdroptype</string>
		<key>UTTypeTagSpecification</key>
		<dict/>
	</dict>
</array>

But that did not work either. Then I tried to add it as a document type in Info.plist

Code Block xml<array>
	<dict>
		<key>CFBundleTypeRole</key>
		<string>None</string>
		<key>LSItemContentTypes</key>
		<array>
			<string>com.devian.sampleapp.customstring.dragdroptype</string>
		</array>
		<key>LSTypeIsPackage</key>
		<integer>0</integer>
	</dict>
</array>

Nothing of the above works on macOS. What am I doing wrong?

Boost

Answer 1

Tapcast-paul OP

Jun ’21

I made just a couple of changes to the plist to get your sample to work:

For the plist, my new fragment looks like this:

<key>UTExportedTypeDeclarations</key>
  <array>
    <dict>
      <key>UTTypeConformsTo</key>
      <array>
        <string>public.data</string>
      </array>
      <key>UTTypeIdentifier</key>
      <string>com.devian.sampleapp.customstring.dragdroptype</string>
    </dict>
  </array>

And that's it, your code unmodified works now.

1