How Has The Nsindexpath Initialization Changed in Swift3

How has the NSIndexPath initialization changed in Swift3?

NSIndexPath has been changed to IndexPath

try IndexPath(row: Int, section: Int)

API Reference : indexpath

Swift 3.0 Developer Preview

Alternative for let indexPath = NSIndexPath(forRow: 0, inSection: 0)

In Swift 3: IndexPath(row: 0, section: 0)

How to init an IndexPath with arrayLiteral

It doesn't expect array but rather a "sequence" of IndexPath.Element types.

let ip = IndexPath(arrayLiteral: 0, 1) // Array [0,1]
// Excerpt from playground: ""ip 0 row 1"\n"
debugPrint("ip \(ip.section) row \(ip.item)")

NSIndexPath in Swift

What I don't understand how NSIndexPath works.

For iOS, you can think of NSIndexPath as a read-only structure that contains two Int properties section and row if you're working with UITableViews or section and item if you're working with UICollectionViews.

You create them with the NSIndexPath:forRow:inSection: factory method:

let indexPath = NSIndexPath(forRow: 1, inSection: 0)

and read them by accessing their properties:

print("row is \(indexPath.row)")

How can I know NSIndexPath has property of row?

Xcode has some nice features to help you understand the code you are looking at. In Xcode, Option-click on row in the above statement line, and it will tell you what it is. In the pop-up, if you click on NSIndexPath UIKit Additions next to Reference, it will bring up the documentation.

Can somebody explain every part of this line please:

let (courseTitle, courseAuthor) = devCourses[indexPath.row]

devCourses is an array of tuples containing two values of type String. You can see this by option-clicking on devCourses and it shows [(String, String)]. Had it been an array of array of String it would have said [[String]] or [Array<String>] (which is two ways of saying the same thing).

indexPath.row is just an Int indicating the selected row of the tableView.

devCourses[indexPath.row] then is the tuple at that index. For example, if the row were 0, then the tuple would be ("iOS App Dev with Swift Essential Training","Simon Allardice").

Finally, you can initialize two variables simultaneously by declaring them as a tuple and initializing them with a tuple. For example:

let (a, b) = (3, 4)

creates two Int constants a and b and assigns 3 to a and 4 to b.

So this statement is retrieving the tuple from the array indicated by the integer indexPath.row and creating two variables, assigning the first variable courseTitle the value of the first value in the tuple and assigning the second variable courseAuthor the value of the second value in the tuple.

Update for Swift 3

NSIndexPath still exists in Foundation, but when working with indexPaths in Swift 3, a new type IndexPath is now used. This type is a structure.

You can still create an NSIndexPath in Swift 3, with the following updated syntax, but you can't change the properties:

var ip = NSIndexPath(row: 0, section: 0)

ip.row = 5    // Cannot assign to property: 'row' is a get-only property

but you should use the new IndexPath structure instead.

IndexPath is created with a similar syntax:

var ip2 = IndexPath(row: 0, section: 0)

ip2.row = 5   // this works

You can convert between IndexPath and NSIndexPath by casting with as:

let ip = NSIndexPath(row: 0, section: 0)
let ip2 = ip as IndexPath     // convert to IndexPath
let ip3 = ip2 as NSIndexPath  // convert back to NSIndexPath

All of the Cocoa and Cocoa Touch API's that use indexPaths have been converted to use IndexPath in Swift.

How to create NSIndexPath for TableView

Use [NSIndexPath indexPathForRow:inSection:] to quickly create an index path.

Edit: In Swift 3:

let indexPath = IndexPath(row: rowIndex, section: sectionIndex)

Swift 5

IndexPath(row: 0, section: 0)

Get [NSIndexPath] array for rows in section of UITableView in Swift

Like this in Swift 3:

func indexPathsForRowsInSection(_ section: Int, numberOfRows: Int) -> [NSIndexPath] {
    return (0..<numberOfRows).map{NSIndexPath(row: $0, section: section)}
}

Conditional Binding: if let error – Initializer for conditional binding must have Optional type

if let/if var optional binding only works when the result of the right side of the expression is an optional. If the result of the right side is not an optional, you can not use this optional binding. The point of this optional binding is to check for nil and only use the variable if it's non-nil.

In your case, the tableView parameter is declared as the non-optional type UITableView. It is guaranteed to never be nil. So optional binding here is unnecessary.

func tableView(tableView: UITableView, commitEditingStyle editingStyle:UITableViewCellEditingStyle, forRowAtIndexPath indexPath: NSIndexPath) {
    if editingStyle == .Delete {
        // Delete the row from the data source
        myData.removeAtIndex(indexPath.row)
        tableView.deleteRowsAtIndexPaths([indexPath], withRowAnimation: .Fade)

All we have to do is get rid of the if let and change any occurrences of tv within it to just tableView.