Presenter: Neha Sinha, Mindfire SolutionsDate: 10/06/2015

Swift vs Objective C

Presenter: Neha Sinha, Mindfire Solutions

One of the goals of the new Swift programming language was to be interoperable with the older Objective-C

What we will deal with in today’s seminar?

• Compare Language Syntax

• Compare Data Types

• Use Swift & Objective C in the same project.

Presenter: Neha Sinha, Mindfire Solutions

Why Care about This?

Many years of Objective-C code

Patterns & practices developed in Objective-C

Swift provides features Objective-C can’t.

Interoperability is not equal

Demand is greater for new Swift to existing Objective-C

Swift understands Objective-C better than Objective-C understands Swift.

Swift provides features Objective-C doesn’t recognize.

Swift:

func getNameAndAge() -> (String, Int) {return (“Neha”, 25)

}

Objective-C:

?

Tuples

Instantiating Objects

Swift:

var myDate = NSDate()

Objective-C:

NSDate* myDate = [NSDate alloc] init];

Using Initializers

Swift:

let myTableView: UITableView = UITableView(frame: CGRectZero, style: Grouped)

Objective-C:

UITableView* myTableView = [[UITableView alloc] initWithFrame:CGRectZero style:UITableViewStyleGrouped];

Mapping Factory Methods

Swift:

let color = UIColor(red: 0.5, green: 0.0, blue: 0.5, alpha: 1.0)

Objective-C:

UIColor* color = [UIColor colorWithRed:0.5 green:0.0 blue:0.5 alpha:1.0];

Factory methods & Objective-C classes are typically just mapped to their equivalent normal Swift initializers.

Failable Initialization

Objective-C:

UIImage* myImage = [UIImage imageWithContentsOfFile:@“”];

An Objective-C initializer can return ‘nil’.Swift demands that variables & constants always exist in a valid state.

Failable Initialization

Swift:

var image: UIImage? = UIImage(contentsOfFile: filePath)if image != nil { return image!}

Calling Methods

Swift:

myTbView.layoutIfNeeded()myTbView.insertSubView(mySubView, atIndex:2)

Objective-C:

[myTbView layoutIfNeeded];[myTbView insertSubView:mySubView atIndex:0];

id & AnyObject Reference

Swift includes a protocol type named AnyObject that represents any kind of object, just as id does in Objective-C.

var myObject: AnyObject = UITableViewCell()myObject = NSDate()

let futureDate = myObject.dateByAddingTimeInterval(10)let timeSinceNow = myObject.timeIntervalSinceNow

id & AnyObject Reference

myObject.characterAtIndex(5)// crash, myObject doesn't respond to that method

let myChar = myObject.characterAtIndex?(5)if let fifthCharacter = myObject.characterAtIndex?(5) { println("Found \(fifthCharacter) at index 5")}

Swift & Objective C Strings

Swift automatically bridges between the String type and the NSString class.

import Foundationlet greeting = "hello, world!"let capitalizedGreeting = greeting.capitalizedString

import Foundationlet myString: NSString = "123"if let integerValue = (myString as String).toInt() { println("\(myString) is the integer \(integerValue)")}

Arrays, Dictionaries & Numbers

Arrays: When you bridge from an NSArray object to a Swift array, the resulting array is of type [AnyObject].

let swiftArray = foundationArray as [AnyObject]if let downcastedSwiftArray = swiftArray as? [NSView] { // downcastedSwiftArray contains only NSView objects}

for aView in foundationArray as! [NSView] { // aView is of type UIView}

This cast is a forced cast, and results in a runtime error if the cast does not succeed.

Arrays, Dictionaries & Numbers

Arrays: When you bridge from a Swift array to an NSArray object, the elements in the Swift array must be AnyObject compatible.

let schoolSupplies: NSArray = ["Pencil", "Eraser", "Notebook"]// schoolSupplies is an NSArray object containing NSString objects

Arrays, Dictionaries & Numbers

Dictionaries: When you bridge from an NSDictionary object to a Swift dictionary, the resulting dictionary is of type [NSObject: AnyObject].

The Swift compiler replaces the NSDictionary class with [NSObject: AnyObject] when it imports Objective-C APIs.

When you cast in the reverse direction, from a Swift dictionary to an NSDictionary object —the keys and values must be instances of a class or bridgeable to an instance of a class.

Arrays, Dictionaries & Numbers

Numbers: Swift automatically bridges certain native number types, such as Int and Float, to NSNumber

All of the following types are automatically bridged to NSNumber:• Int• UInt• Float• Double• Bool

let n = 42let m: NSNumber = n

Working with NSError in Swift

Error reporting in Swift follows the same pattern it does in Objective-C, with the added benefit of offering optional return values.

var writeError: NSError?let written = myString.writeToFile(path, atomically: false, encoding: NSUTF8StringEncoding, error: &writeError)if !written { if let error = writeError { println("write failure: \(error.localizedDescription)") }}

Swift & Objective C: Mix and Match

You can ‘Mix n Match’ Objective-C & Swift in the same project.

• Bridging header file — Swift & Objective-C need to be informed about other classes in the same project in a different way.

• We use 2 bridging headers — One lets our Objective-C classes know about Swift & the other vice-versa.

Inheriting between Languages

Swift:

class MySwiftViewController: UIViewController { // define the class}

Objective-C:

@class MySwiftClass;@interface MyObjcClass : NSObject{ // define the class}

Migrating from Objective C to Swift

The most effective approach for migrating code to Swift is on a per-file basis, that is, one class at a time.

Because you can’t subclass Swift classes in Objective-C, it’s best to choose a class in your app that doesn’t have any subclasses. You’ll replace the .m and .h files for that class with a single .swift file.

The Future Favors Swift

Swift: The more approachable, full-featured language

• Easier to maintain

• Is Considered Safer & Faster

• Is Unified with Memory Management

• Encourages interactive coding

Presenter: Neha Sinha, Mindfire Solutions

Questions?

References

https://developer.apple.com/library

http://www.infoworld.com/article/2920333/mobile-development/swift-vs-objective-c-10-reasons-the-future-favors-swift.html?page=2

http://mobileoop.com/the-comparison-between-swift-and-objective-c-programming-language

Presenter: Neha Sinha, Mindfire Solutions

Thank You

www.mindfiresolutions.com

https://www.facebook.com/MindfireSolutions

http://www.linkedin.com/company/mindfire-solutions

http://twitter.com/mindfires