BhaveshDhaduk/KDDragAndDropCollectionView

Drag and Drop Collection Views

Written for Swift 4.0, it is an implementation of Dragging and Dropping data across multiple UICollectionViews.

Requirements

iOS 8.0+
XCode 9.0+
Swift 4.0 +

Installation

Cocoa Pods

pod 'KDDragAndDropCollectionViews', '~> 1.0'

Manual

Add KDDragAndDropManager.swift and KDDragAndDropCollectionView.swift to your project.

Quick Guide

Make the UICollectionView of interest a KDDragAndDropCollectionView

Then set a class as dataSource implementing the KDDragAndDropCollectionViewDataSource protocol.

class ViewController: UIViewController, KDDragAndDropCollectionViewDataSource {

    @IBOutlet weak var firstCollectionView: KDDragAndDropCollectionView!
    @IBOutlet weak var secondCollectionView: KDDragAndDropCollectionView!
    @IBOutlet weak var thirdCollectionView: KDDragAndDropCollectionView!
    
    var data : [[DataItem]] = [[DataItem]]() // just for this example
    
    var dragAndDropManager : KDDragAndDropManager?
    
    override func viewDidLoad() {
        let all = [firstCollectionView, secondCollectionView, thirdCollectionView]
        self.dragAndDropManager = KDDragAndDropManager(canvas: self.view, collectionViews: all)
    }
}

The only responsibility of the user code is to manage the data that the collection view cells are representing. The data source of the collection views must implement

protocol KDDragAndDropCollectionViewDataSource : UICollectionViewDataSource {
    
    func collectionView(collectionView: UICollectionView, indexPathForDataItem dataItem: AnyObject) -> NSIndexPath?
    func collectionView(collectionView: UICollectionView, dataItemForIndexPath indexPath: NSIndexPath) -> AnyObject
    
    func collectionView(collectionView: UICollectionView, moveDataItemFromIndexPath from: NSIndexPath, toIndexPath to : NSIndexPath) -> Void
    func collectionView(collectionView: UICollectionView, insertDataItem dataItem : AnyObject, atIndexPath indexPath: NSIndexPath) -> Void
    func collectionView(collectionView: UICollectionView, deleteDataItemAtIndexPath indexPath: NSIndexPath) -> Void
    
}

In the example we have 3 UICollectionViews distinguishable by their tags (bad practice, I know... but it's only an example ;-) and a data array holding 3 arrays respectively. In a case like this, an implementation of the above could be:

func collectionView(collectionView: UICollectionView, dataItemForIndexPath indexPath: NSIndexPath) -> AnyObject {
    return data[collectionView.tag][indexPath.item]
}

func collectionView(collectionView: UICollectionView, insertDataItem dataItem : AnyObject, atIndexPath indexPath: NSIndexPath) -> Void {
    if let di = dataItem as? DataItem {
        data[collectionView.tag].insert(di, atIndex: indexPath.item)
    }
}

func collectionView(collectionView: UICollectionView, deleteDataItemAtIndexPath indexPath : NSIndexPath) -> Void {
    data[collectionView.tag].removeAtIndex(indexPath.item)
}

func collectionView(collectionView: UICollectionView, moveDataItemFromIndexPath from: NSIndexPath, toIndexPath to : NSIndexPath) -> Void {
    let fromDataItem: DataItem = data[collectionView.tag][from.item]
    data[collectionView.tag].removeAtIndex(from.item)
    data[collectionView.tag].insert(fromDataItem, atIndex: to.item)    
}

func collectionView(_ collectionView: UICollectionView, indexPathForDataItem dataItem: AnyObject) -> IndexPath? {

    guard let candidate = dataItem as? DataItem else { return nil }
    
    for (i,item) in data[collectionView.tag].enumerated() {
        if candidate != item { continue }
        return IndexPath(item: i, section: 0)
    }
    return nil
}

Data Items and Equatable

In the example code included in this project, I have created a DataItem class to represent the data displayed by the collection view.

class DataItem : Equatable {
    var indexes: String
    var colour: UIColor
    init(indexes: String, colour: UIColor = UIColor.clear) {
        self.indexes    = indexes
        self.colour     = colour
    }
    static func ==(lhs: DataItem, rhs: DataItem) -> Bool {
        return lhs.indexes == rhs.indexes && lhs.colour == rhs.colour
    }
}

In the course of development you will be making your own types that must comform to the Equatable protocol as above. Each data item must be uniquely idenfyiable so be careful when creating cells that can have duplicate display values as for example a "Scrabble" type game where the same letter appears more than once. In cases like these, a simple identifier will do to implement the equality.

Make your Own

If you want to dig deeper into the logic that was followed, a full tutorial on how it was built can be found at the karmadust blog.

License

The MIT License (MIT)

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

BhaveshDhaduk / KDDragAndDropCollectionView