A working implementation of drag and drop between two LazyVGrid elements in SwiftUI

DragAndDropBetweenLazyVGrids.swift

//
//  DragAndDropView.swift
//  DragAndDropView_Example
//
//  Created by Wessley Roche on 11/5/23.
//

import SwiftUI
import UniformTypeIdentifiers

struct DragAndDropView: View {
	@State private var leftItems = Array(1...10)
	@State private var rightItems = Array(11...20)
	
	@State var draggedItem: Int?
	
	let columns = [
		GridItem(.adaptive(minimum: 80))
	]
	
	var body: some View {
		HStack {
			GeometryReader { geometry in
				LazyVGrid(columns: columns, spacing: 20) {
					ForEach(leftItems, id: \.self) { item in
						Text("\(item)")
							.frame(maxWidth: .infinity, minHeight: 50)
							.background(Color.green)
							.cornerRadius(8)
							.onDrag {
								draggedItem = item
								return NSItemProvider(object: String(item) as NSString)
							}
							.opacity(draggedItem == item ? 0 : 1)
					}
				}
				.frame(minHeight: 80)
				.background(Color.gray)
				.onDrop(of: [.text], delegate: MyDropDelegato(draggedItem: $draggedItem, items: $leftItems, geometry: geometry))
			}
			
			GeometryReader { geometry in
				LazyVGrid(columns: columns, spacing: 20) {
					ForEach(rightItems, id: \.self) { item in
						Text("\(item)")
							.frame(maxWidth: .infinity, minHeight: 50)
							.background(Color.green)
							.cornerRadius(8)
							.onDrag {
								draggedItem = item
								return NSItemProvider(object: String(item) as NSString)
							}
							.opacity(draggedItem == item ? 0 : 1)
					}
				}
				.frame(minHeight: 80)
				.background(Color.gray)
				.onDrop(of: [.text], delegate: MyDropDelegato(draggedItem: $draggedItem, items: $rightItems, geometry: geometry))
			}
		}
		.padding()
	}
}

struct MyDropDelegato: DropDelegate {
	/// The item currently being dragged
	@Binding var draggedItem: Int?
	
	/// The items in the grid
	@Binding var items: [Int]
	
	/// The geometry of the grid
	var geometry: GeometryProxy
	
	func performDrop(info: DropInfo) -> Bool {
		withAnimation {
			/// Reset dragged item
			draggedItem = nil
		}
		return true
	}
	
	func dropUpdated(info: DropInfo) -> DropProposal? {
		/// Get the index from the drop info location
		let destination = getIndexForItem(itemPosition: info.location)
		
		withAnimation {
			if let item = draggedItem, let origin = items.firstIndex(of: item) {
				let adjustedDestination = destination < origin ? destination : min(destination + 1, items.count)
				items.move(fromOffsets: IndexSet(integer: origin), toOffset: adjustedDestination)
			}
		}
		return DropProposal(operation: .move)
	}
	
	func dropEntered(info: DropInfo) {
		guard let item = draggedItem else { return }
		if items.firstIndex(of: item) == nil {
			items.append(item)
		}
	}
	
	func dropExited(info: DropInfo) {
		guard let item = draggedItem else { return }
		if let index = items.firstIndex(of: item) {
			items.remove(at: index)
		}
	}
	
	func getIndexForItem(itemPosition: CGPoint) -> Int {
		let itemWidth: CGFloat = 80
		let itemHeight: CGFloat = 50
		let spacing: CGFloat = 20
		
		let numberOfColumns = Int(geometry.size.width / itemWidth)
		let column = Int(itemPosition.x / itemWidth)
		let row = Int(itemPosition.y / (itemHeight + spacing))
		
		let index = row * numberOfColumns + column
		return index
	}
}

struct DragAndDropView_Previews: PreviewProvider {
	static var previews: some View {
		DragAndDropView()
	}
}