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    23Jun, 2017
    Drag and Drop in UICollectionView in iOS 11

    What’s New:

    iOS 11 introduced the drag and drop feature that lets you drag , drop the content from one application to other application on iPad. This article provides the high level overview with example code on this to drag and drop the UICollectionViewCells in UICollectionView.

    Click this see the drag and drop video in action for the code in the article.

    Delegates:

    • dragDelegate – This delegate manages the dragging of items from collection view.
    • dropDelegate – This delegate manages the dropping of items to collection view

    Protocols:

    • UICollectionViewDragDelegate – This protocol requires the implementation of below method that provides the item to be dragged
    public func collectionView(_ collectionView: UICollectionView, itemsForBeginning session: UIDragSession, at indexPath: IndexPath) -> [UIDragItem]
    •  UICollectionViewDropDelegate – This protocol requires implementation of below method that holds the items being dropped to CollectionView.
    func collectionView(_ collectionView: UICollectionView, performDropWith coordinator: UICollectionViewDropCoordinator)

     

    Example:

    Let’s explore the drag and drop feature by creating a collection view that holds images. Drag and drop allows the images from other applications (like photos..etc) to be added to our collectionView by dragging and vice-versa in other direction for dropping

    Steps:

    1. Implement the CollectionView with each cell holding some image.
    2. Set the drag and drop delegates to the object that provides the implementation of UICollectionViewDragDelegate, UICollectionViewDropDelegate. In this example, we are setting the delegates to self.

    collectionView.dragDelegate = self

    collectionView.dropDelegate = self

    1. Implement the both the new delegates. Code provided below with explanation following it.

    Explanation:

    Drag:

    collectionview(_:itemsForBeginning:at:)  This method expects the UIDragItem to identify the content that needs to be carried while dragging the cell.

    This above method is enough to allow the image to be dragged from UICollectionViewCell to any other application to which image can be dropped

    Drop:

    collectionView(_:performDropWith:)  This method has the implementation of capturing the image dropped by other application and creating the new UICollectionViewCell and add the image to it.

    This article provides the basic introduction to drag and drop feature. Complete code can be obtained from GitHub link  Let me know in comments for any queries. Happy coding!!

     

    14Jun, 2017
    What’s New In Swift4

    This article is to highlight the key features added/ modified in Swift 4. Apple scheduled to release Swift 4 in fall 2017 and its beta versions are already available for download for developers.

    Downloading Swift 4 Snapshot

    Swift 4.0 Snapshots are prebuilt binaries that are automatically created from swift-4.0-branch branch. Latest snapshot package downloaded from Swift 4.0 Development section from here.

    Run downloaded installer file to install the snapshot. Now goto Xcode->Toolchains and select the snapshot as in below screenshot.

    There is nothing more to do; you are all set to play with Swift 4. Create new playground file and test it out yourself all the new Swift 4 features.

    Here, I covered the important new/modified features and I will keep adding here as I get more details

    Strings

    String is a collection

    Strings are now collections in Swift 4 like it was in Swift 2. This allows iterating though characters in string. Just like any other collection, string can reversed, apply map() and flatmap() !

    
let swift4String = "String is collection of characters in Swift4"
for char in swift4String.reversed() {
    print(char) // prints each character in reversed string
}

    Multi-line string literals

    Swift 3 requires line break (\n) to write multi-line strings. In Swift 4 introduces triple quotes (“””) to start and end of the multiline string. It lets use quote marks without escaping.

    The indentation of the closing delimiter determines how much whitespace is stripped from the start of each line.

    var multiStr =
"""
This string starts with a line feed.
It also ends with a line feed.
"""

print(multiStr)
    This image demonstrates on how indentation works

    Substring is new type

    Swift 4 introduced Substring type to represent the String slices.

    
var str = "Hello, playground"
let commaIndex = str.index(of: ",")!
let substring = str.substring(to: commaIndex)  // Hello
print(type(of: substring))    //String

let substringRange = str[..<commaIndex]
print(type(of: substringRange))  //Substring

    The need for introducing Substring is to optimize memory for Strings. I will create a separate article on memory management and talk about Substring there.

    Unicode 9 Characters

    Each String emoticon is now 1 character in Swift 4.

    "👩‍👩‍👧".count  //is 1 in Swift 4
"👩‍👩‍👧".characters.count   //is 3 in swift 3