Drag&Drop works with URL, but not with String – why? - macos

Question

In my code the drag&drop function works fine with URL objects. But the exact same code for String objects does not. I have tried with countless casts and loadItem instead of loadObject ... no luck so far.
Can anyone help me here? It would be very much appreciated.
code for URL objects – Working
.onDrag {
return NSItemProvider(object: item.url as NSURL)
}
.onDrop(of: [UTType.url], isTargeted: $isDropping) { providers in
_ = providers.first?.loadObject(ofClass: URL.self) { url, error in
if let error = error { print(error.localizedDescription) }
if let url = url {
DispatchQueue.main.async {
self.array2.insert(Item(title: "new", url: url), at: 0)
}
}
}
return true
}
the same with String does not:
.onDrag {
return NSItemProvider(object: item.title as NSString)
}
.onDrop(of: [UTType.text], isTargeted: $isDropping) { providers in
_ = providers.first?.loadObject(ofClass: String.self) { string, error in
if let error = error { print(error.localizedDescription) }
if let string = string {
DispatchQueue.main.async {
self.array2.insert(Item(title: string, url: URL(string: "http://www.apple.com")!), at: 0)
}
}
}
return true
}
full MRE code:
import SwiftUI
import UniformTypeIdentifiers
struct Item: Identifiable {
let id = UUID()
var title: String
var url: URL
}
struct ContentView: View {
#State var array1: [Item] = [
Item(title: "One", url: URL(string: "http://www.amazon.com")!),
Item(title: "Two", url: URL(string: "http://www.apple.com")!),
Item(title: "Three", url: URL(string: "http://www.example.com")!),
]
#State var array2: [Item] = []
#State var isDropping = false
var body: some View {
HStack(alignment: .top) {
VStack(alignment: .leading) {
ForEach(array1) { item in
Text(item.title)
Text(item.url.absoluteString).foregroundColor(.secondary)
// DRAG
.onDrag {
return NSItemProvider(object: item.url as NSURL) // WORKS
// return NSItemProvider(object: item.title as NSString) // DOES NOT WORK
}
}
}
.frame(maxWidth: .infinity)
Divider()
VStack(alignment: .leading) {
ForEach(array2) { item in
Text(item.title)
Text(item.url.absoluteString).foregroundColor(.secondary)
}
}
.frame(maxWidth: .infinity, maxHeight: .infinity)
.background(isDropping ? .green : .gray)
// DROP with url/NSURL -- WORKS
.onDrop(of: [UTType.url], isTargeted: $isDropping) { providers in
_ = providers.first?.loadObject(ofClass: URL.self) { url, error in
if let error = error { print(error.localizedDescription) }
if let url = url {
DispatchQueue.main.async {
self.array2.insert(Item(title: "new", url: url), at: 0)
}
}
}
return true
}
// DROP with text/NSString -- DOES NOT WORK
.onDrop(of: [UTType.text], isTargeted: $isDropping) { providers in
_ = providers.first?.loadObject(ofClass: String.self) { string, error in
if let error = error { print(error.localizedDescription) }
if let string = string {
DispatchQueue.main.async {
self.array2.insert(Item(title: string, url: URL(string: "http://www.apple.com")!), at: 0)
}
}
}
return true
}
}
}
}

Answer 1

As always thanks to #Asperi and his answer here:
SwiftUI: Not getting dropped NSString value in DropDelegate
This now works:
.onDrop(of: [UTType.utf8PlainText], isTargeted: $isDropping) { providers in
_ = providers.first?.loadItem(forTypeIdentifier: "public.utf8-plain-text") { data, error in
if let error = error { print(error.localizedDescription) }
if let data = data as? Data {
DispatchQueue.main.async {
let string = NSString(data: data, encoding: 4) ?? "failed"
print(string)
self.array2.insert(Item(title: string as String, url: URL(string: "http://www.apple.com")!), at: 0)
}
}
}
return true
}