iOS8 Swift Cheat Sheet

iOS8 Swift Cheat Sheet and Quick Reference Guide for iPhone Developers. Swift is the new programming language used in developing applications for Mac OS and iOS,

Arrays

var colors = ["red", "blue"]
var moreColors: String[] = ["orange", "purple"] // explicit type
colors.append("green") // [red, blue, green]
colors += "yellow" // [red, blue, green, yellow]
colors += moreColors // [red, blue, green, yellow, orange, purple]

var days = ["mon", "thu"]
var firstDay = days[0] // mon
days.insert("tue", atIndex: 1) // [mon, tue, thu]
days[2] = "wed" // [mon, tue, wed]
days.removeAtIndex(0) // [tue, wed]

Classes

class Counter {
  var count: Int = 0 
  func inc() { 
    count++
  }
  func add(n: Int) {
    count += n
  }
  func printCount() {
    println("Count: \(count)")
  }
}

var myCount = Counter()
myCount.inc()
myCount.add(2)
myCount.printCount() // Count: 3    
   

Conditionals

//IF STATEMENT
let happy = true
if happy {
 println("We're Happy!")
} else {
 println("We're Sad :('")
}
// We're Happy!

let speed = 28
if speed <= 0 {
 println("Stationary")
} else if speed <= 30 {
 println("Safe speed")
} else {
 println("Too fast!")
}
// Safe speed


//SWITCH STATEMENT
let n = 2
switch n {
 case 1:
  println("It's 1!")
 case 2...4:
   println("It's between 2 and 4!")
 case 5, 6:
  println("It's 5 or 6")
 default:
  println("Its another number!")
}
// It's between 2 and 4!

Constants

let myInt = 1
myInt = 2 // compile-time error!

Dictionaries

var days = ["mon": "monday", "tue": "tuseday"] 
days["tue"] = "tuesday" // change the value for key "tue"
days["wed"] = "wednesday" // add a new key/value pair

var moreDays: Dictionary = ["thu": "thursday", "fri": "friday"]
moreDays["thu"] = nil // remove thu from the dictionary
moreDays.removeValueForKey("fri") // remove fri from the dictionary

Enums

enum CollisionType: Int { 
 case Player = 1 
 case Enemy = 2 
} 
var type = CollisionType.Player

For Loops

for var index = 1; index < 3; ++index {
 // loops with index taking values 1,2 
}
for index in 1..3 {
 // loops with index taking values 1,2
}
for index in 1...3 { 
 // loops with index taking values 1,2,3
}

let colors = ["red", "blue", "yellow"]
for color in colors {
    println("Color: \(color)")
}
// Color: red
// Color: blue
// Color: yellow 

let days = ["mon": "monday", "tue": "tuesday"]
for (shortDay, longDay) in days {
    println("\(shortDay) is short for \(longDay)")
}
// mon is short for monday
// tue is short for tuesday

Functions

func iAdd(a: Int, b: Int) -> Int {
  return a + b
}
iAdd(2, 3) // returns 5

func eitherSide(n: Int) -> (nMinusOne: Int, nPlusOne: Int) {
  return (n-1, n+1)
}
eitherSide(5) // returns the tuple (4,6)    

Logical Operators

var happy = true
var sad = !happy // logical NOT, sad = false
var everyoneHappy = happy && sad // logical AND, everyoneHappy = false
var someoneHappy = happy || sad // logical OR, someoneHappy = true

Printing

let name = "swift"
println("Hello")
println("My name is \(name)")
print("See you ")
print("later")
/*  
 Hello
 My name is swift
 See you later 
*/

Strings

var myString = "a"
let myImmutableString = "c"
myString += "b" // ab
myString = myString + myImmutableString // abc
myImmutableString += "d" // compile-time error!

let count = 7
let message = "There are \(count) days in a week"

Variables

var myInt = 1 
var myExplicitInt: Int = 1 // explicit type
var x = 1, y = 2, z = 3 // declare multiple integers
myExplicitInt = 2 // set to another integer value

Developing iOS8 Hello World! Using Swift

Apple recently announced a pretty major change to the way iOS apps have been developed in the past, an entirely different programming language called Swift which replaces Objective-C. 
In my efforts to learn the new language, I’ve decided I will be posting regularly as I step through the learning process, sharing everything I find. This is the first post of many on the topic, and I hope you decide to follow along!

           

The Basics

Declaring Variables:

iOS8 Swift does away with the standard of declaring variables by starting with their type names, and instead opts to use a Javascript-like ‘var’ keyword to define any variable.

Objective-c: NSString *firstString=@"My first string";

Swift: var firstString="My first string"

Declaring Constants:

Objective-c: NSInteger *const myfirstconstant;

Swift: let ksomeconstant:int=10;

Meanwhile constants are expressed with the ‘let’ keyword.

Declaring arrays and dictionary:

Objective-c: NSArray *Myarray=[[NSArray alloc]init];

                    NSDictionary *Mydictionary=[[NSDictionary alloc]init];

Swift:   var Myarray=["one","two","three"]

            var Mydictionary=["primary number:one","secondary number:two"]

There’s a lot more to go over, but I think these basics are important to get a start going on to the tutorial. So with that, let’s move on to Hello World.

HELLO WORLD Program in Objective-c and Swift:

Objective-c:

#import

#import<Foundation/Foundation.h>

int main(void)

{

NSLog(@"Hello,World!\n");

return 0;

}

Swift:

1.Create a new x-code project in single view application.

2.Select SWIFT language.

3.Find AppDeligate.swift file inside the project

    Inside of this file find the line that says:

    “// Override point for customization after application launch.”

4.Replace this line with our amazing hello world code:

      println("Hello World")

Now press run and you should see a blank app boot up, and the words “Hello World” print to the console. Congratulations! You just wrote your first iOS8 Hello World application in Swift!

  

Swift: Apple's new programming language

Apple surprised developers by unveiling a successor to Objective-C, the programming language used across the Apple ecosystem, but what are the benefits of it?

      

Apple took developers by surprise on Tuesday by announcing Swift, a new programming language for developing apps across Apple’s platforms.

Until now, most apps on Apple devices have been built using Objective-C, the language almost exclusively adopted by NeXT corporation years ago and subsequently by Apple.

Objective-C now seems to be on its way out, superseded by a language that looks to be "safe, modern and powerful", according to Apple’s engineering chief, Craig Federighi. But how powerful is this new language, and what difference will it make to the global community of developers building for Apple products.

What is Swift?

Swift is Apple’s new programming language, which has been in development for the past four years and which looks to replace Objective-C as the main language for app development on Apple’s platforms, OSX and iOS.

It’s a major departure from the syntax of Objective-C and takes a lot of cues from other languages, such as Haskell, C#, Ruby and Python, which Apple presumably hopes will make it appealing to bright young coders, keen on modern languages.

Although it’s a major departure, Apple have taken a lot of trouble to make the transition to Swift as painless as possible. It is fully binary compatible with existing Objective-C libraries and maintains a close relationship with the Cocoa frameworks.

That means that developers can introduce Swift into their apps at their own pace, by writing discrete modules that should seamlessly interoperate with their existing Objective-C code.

Importance for safety

Swift eliminates entire classes of unsafe code. Variables are always initialized before use, arrays and integers are checked for overflow, and memory is managed automatically. Syntax is tuned to make it easy to define your intent — for example, simple three-character keywords define a variable (var) or constant (let).

The safe patterns in Swift are tuned for the powerful Cocoa and Cocoa Touch APIs. Understanding and properly handling cases where objects are nil is fundamental to the frameworks, and Swift code makes this extremely easy. Adding a single character can replace what used to be an entire line of code in Objective-C. This all works together to make building iOS and Mac apps easier and safer than ever before.

What are the other improvements Compare to Objective-C?

Type Inference

In Swift there is no need to annotate variables with type information as the compiler can infer type based on the value a variable is being set to. Due to the dynamic nature of Objective-C, type is not truly known at compile time because methods may be added to existing classes, entirely new classes added or instance type changed all at runtime.

Type Safety

With Swift, the compiler can be more helpful in catching subtle type related bugs. As the compiler knows more about type in any method call, it can optimise certain call sites and jump directly to the implementation using C++ style vtable dispatch, rather than going through dynamic dispatch as in Objective-C. This enables smart optimisations that can make code run faster.

Control Flow

The humble switch statement has undergone a radical overhaul in Swift and can now match against ranges, list of elements, boolean expression, enums amongst others. It doesn’t fall through by default, and is further enhanced by Swift’s flexible pattern matching.

Optionals

An optional type is a type that might contain a value of a type. It allows you to more easily convert between types and avoid null checks. Optionals can be chained together to protect from exceptions when calling multiple methods or properties in a chain where one call might return “nil”.

Strings

Strings are now easier to deal with in Swift, with a cleaner syntax than Objective-C, eg: concatenate strings using “+=“.

Best to ios Games

As alluring as the 'write once, run anywhere' promise is, apps based on web technologies have historically performed less admirably than their native counterparts. These performance issues have made it impossible to use web technologies for some types of apps. Games, in particular, are notoriously picky about responsiveness and developers often need to squeeze as much performance out of the CPU/GPU as possible. It's likely no accident that Apple chose to showcase a game for their programming demo.

However, the overwhelming majority of developers aren't creating games. Furthermore, many developers aren't launching their apps with a high degree of certainty. In the beginning, the goal is adoption and learning. During this formative stage, developers aren't doing themselves any favors by committing to a platform-specific language and limiting their potential audience.

At the same time, HTML keeps getting better and better. In fact, during WWDC, Apple announced that iOS8 would extend the performance benefits of Safari to all Webkit based apps. This enhancement is going to improve all apps based on web technologies.

Swift is a great move for Apple and exciting news to developers who are willing to commit exclusively to iOS. But most mobile developers are better served by cross-platform technologies which enable them to engage with everyone; not just the Apple crowd.