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mmick66
447 Stars 73 Forks MIT License 148 Commits 1 Opened issues

Description

This component allows for the transfer of data items between collection views through drag and drop

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Drag and Drop Collection Views

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

Drag and Drop Illustration

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Language Licence CocoaPods Awesome

Requirements

  • iOS 8.0+
  • XCode 9.0+
  • Swift 4.0 +

Installation

Cocoa Pods

pod 'KDDragAndDropCollectionViews', '~> 1.5.2'

Manual

Add the files in

Classes/
to your project.

Quick Guide

Make the UICollectionView of interest a

KDDragAndDropCollectionView

XCode Interface Builder Screen

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 the

KDDragAndDropCollectionViewDataSource
protocol.

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

}

Advanced Use

Prevent specific Items from being Dragged and/or Dropped

For a finer tuning on what items are draggable and which ones are not we can implement the following function from the

KDDragAndDropCollectionViewDataSource
protocol
func collectionView(_ collectionView: UICollectionView, cellIsDraggableAtIndexPath indexPath: IndexPath) -> Bool {
    return indexPath.row % 2 == 0
}

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.

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