Meet Transferable

• sharing is now supported on watchOS 9

Content type (Uniform type identifier - UTI)

• Apple-specific technology that describes identifiers for different binary structures as well as abstract concepts

• in order to declare a custom identifier:

  1. add its declaration to your app Info.plist file

  2. (recommended) create a file extension: if the data is saved on disk, the system will know that your app can open that file

  3. declare it in code

import UniformTypeIdentifiers

// also declare the content type in the Info.plist
extension UTType {
  static var profile: UTType = UTType(exportedAs: "com.example.profile")
}

Transferable

• Swift-first declarative way to describe how your models can be serialized and deserialized for sharing and data transfer

• supports standard Transferable types: String, Data, URL, Attributed String, Image

Use example

• new PasteButton:

var body: some View {
  // 👇🏻 allow pasting a Transferable type
  PasteButton(payloadType: String.self) { pastedString in
    // ...
  }
}

• new draggable(_:) and dropDestination(payloadType:action:isTargeted:) modifiers:

struct PortraitView: View {
  @State var portrait: Image // 👈🏻 Transferable type

  var body: some View {
    portrait
      .cornerRadius(8)
      .draggable(portrait) // 👈🏻 drag support
      .dropDestination(payloadType: Image.self) { (images: [Image], _) in // 👈🏻 drop support
        if let image = images.first {
          portrait = image
          return true
        }
        return false
      }
  }
}

• new ShareLink:

var body: some View {
  VStack {
    portrait
    Text(model.name)
  }
  .toolbar {
    ShareLink(item: portrait, preview: SharePreview(model.name))
  }
}

Conforming custom types to Transferable

• Transferable definition:

public protocol Transferable {
  associatedtype Representation: TransferRepresentation

  @TransferRepresentationBuilder<Self> static var transferRepresentation: Self.Representation { get }
}

public protocol TransferRepresentation: Sendable {
  associatedtype Item: Transferable
  associatedtype Body: TransferRepresentation

  @TransferRepresentationBuilder<Self.Item> var body: Self.Body { get }
}

• to conform a type to Transferable, there’s only one property to implement: transferRepresentation (of type TransferRepresentation)

• There are three important representations to be aware of:

• CodableRepresentation

• DataRepresentation

• FileRepresentation

• if our type conforms to Codable, we can use the CodableRepresentation

  • by default Transferable uses a JSONEncoder/JSONDecoder , but you can provide your own

import CoreTransferable
import UniformTypeIdentifiers

struct Profile: Codable, Transferable { // 👈🏻
  var id: UUID
  var name: String
  var bio: String
  var funFacts: [String]
  var video: URL?
  var portrait: URL?

  // MARK: Transferable

  static var transferRepresentation: some TransferRepresentation { // 👈🏻
    CodableRepresentation(contentType: .profile)
  }
}

// also declare the content type in the Info.plist
extension UTType {
  static var profile: UTType = UTType(exportedAs: "com.example.profile")
}

• DataRepresentation vs. FileRepresentation

  • choose the former if the model is always in-memory

  • choose the latter if the model can be stored on disk

  • FileRepresentation is intended to work with the URLs written to disk, and ensure receivers’ access to this file or its copy by granting a temporary sandbox extension

• we can pass multiple representations in the transferRepresentation property

  • the receiver will use the first representation with the content type they support.

import CoreTransferable
import UniformTypeIdentifiers

struct Profile: Codable {
  var id: UUID
  var name: String
  var bio: String
  var funFacts: [String]
  var video: URL?
  var portrait: URL?
}

extension Profile: Transferable {
  static var transferRepresentation: some TransferRepresentation {
  CodableRepresentation(contentType: .profile) // 👈🏻 first representation
  ProxyRepresentation(exporting: \.name) // 👈🏻 alternative representation
  }
}

// also declare the content type in the Info.plist
extension UTType {
  static var profile: UTType = UTType(exportedAs: "com.example.profile")
}