Swift basics - the very basics (variables, constants, types)

To open the debug area:
shift+command+Y

Add images to swift playground:
1. command + 1
2. Drop image over to resources folder
3. Create an object with the image:
var image = UIImage(named: "sc.png")

Using the for loop:

var j = 1
for i in 1...5
{
  j += i
}

for in loop: used with collection or range of numbers:

for index in 1...5
{
  print(index)
}

for item in firstArray{}
for (index, value) in dict1{}

while x<7
{
  x = Int(arc4random_uniform(10))
}

ar4random above gives a random number between 0 and 9

Instead of do while, swift makes use of repeat while
var x: Int
repeat
{
  x = Int(arc4random_uniform(10))
} while x < 4


Add comments:
//
/* */
///
The triple slash is for documenting code
For example:
To document a function:

///

///The adding function will the take 2 parameters

/// - parameter nameOfFirst: First number to add

/// - parameter secondParameter: Second number to add

/// - returns: the sum of the two numbers

/// - throws: any error

///

When you press the option key and click on the function name, information on the function as above will appear.

Creating a function

func adding(nameOfFirst: Int, secondParameter: Int) -> Int
{
  let sum: Int = nameOfFirst + secondParameter
  return sum
}

adding(nameOfFirst: 4, secondParameter: 6)

Use of semicolons: Can be used but unnecessary

If else:

if i == 1
{

}

While statement:
while i == 1
{

}

Printing a line inside playground:
print("Hello world")

Add a variable to a string:
var day = "Wednesday"
var msg1 = "Today is \(day)"

Print 3 variables separated by a comma:
print(day1, day2, day3, separator:", ", terminator:"")
Direct the output to a variable:
var nameOfVar = ""
print(day1, day2, day3, separator:", ", terminator:"", to:&nameOfVar)

Naming rules for variables:

Must not contain whitespace.

Must not contain mathematical symbols or arrows.

Must not have private-use or invalid unicode characters.

Must not start with a number, but can contain numbers.

Don't use Swift keywords as identifiers, like class.

Define a constant which will not change once a value is assigned to it:

let valueOfPi = 3.142

Define a variable

var numberOfGuests = 50

Declaring multiple constants:

let valueOfPi = 3.142, speedOfGravity = 10

Declaring multiple variables:

var num1 = 1, num2 = 2

Variables are defined by their initial values.

To indicate the type explicitly:

var valueOfPi: Float = 3.14

//so the above won't be turned into a double

Here are the different types of integers:

Int8

Int16

Int32

Int

UInt8

UInt16

UInt32

UInt64

UInt

To get the minimum or maximum possible values of each type:

UInt8.max

UInt16.min

To print it out:

print("\(UInt8.max)")

You can also insert arbitrary underscores in numbers:

let speedOfLight = 300_000

The underscores are ignored

Difference between float and double:

Float is used to represent a 32 bit floating-point number.

Double is used to represent a 64 bit floating-point number.

Float80 represents an 80 bit floating-point number.

How to add an Integer and a Double:

var a: Int = 1

var b: Double = 0.14

var c = Double(a) + b

var d = 32

var e = Float(d)

var f = UInt16(d)

Using boolean variables in if else code:

var abc = true

if abc

{

}

Operators

assignment 

let x = 1

Comparison:

==

!=

>

<

>=

<=

Arithmetic

+ - * /

Remainder

var x = 20 % 6

Compound assignment

+=

-=

*=

/=

Ternary operator:

When you assign a value depending on whether a criteria is met:

var a = 1

var b = 2

var c = (b>a ? "B is greater" : "A is greater")

Logical operators:

NOT

a = !b

(if b is true, a is false)

AND

var a = true

var b = false

var c = a && b 

//(false)

OR

var a = true

var b = false

var c = a || b 

//(false)