swift_notes.md

Swift

Overview

print("Hello world!") 
var variable = 5
let constant = 10

Casting

word = "Hello World \(constant + variable)" + String(variable)

Arrays and Dictionaries

list = []
dictionary = [:]
list = [String]()
dictionary = [String: Int]()
var list = [“fish”, “dog”, “cat”]
var dictionary = [list[0]: 3, list[1]: 2, list[2]: 1]

Control Flow

• () around condition optional, but must have {} around body
• for-in to iterate through lists and dictionaries

for i in list { 
	pass
}
for (x,y) in dictionary { 
	pass
}

• while loops are normal

Looping a range of indexes

for i in 0..<4 { 
	print(i) //exclusive top
}
for i in 0...4 {
	print(i) //inclusive top
}

Switch Case

• must be exhaustive and have default case

switch (4) {
case let x where x%2==0: 
	print("\(x) is an even number!") //checks if the switch thing is divisible by 2 and makes it x
default: 
	print("it is an odd number")
}

Optionals

var optionalThing: Int? = 5

if let thing = optionalThing { //checks if optionalThing is not nil
	print(thing)
} 

Functions

func greet(name: String, day: String) -> String { 
	return "Hello \(name), today is \(day)!"
} 
greet("Joanna", day: "Monday") 

• functions can return a tuple, whose elements can be referred to by name or number

• functions can take a variable number of arguments and put them in an array

func sumOf(numbers: Int...) -> Int { 
	var sum = 0
	for num in numbers { 
		sum += num
	}
	return sum
}
sumOf(1)
sumOf(2, 54, 332)

• functions can be nested
• functions are first-class type, function can return another function as value and can also take function in as argument
• parameters can have an argument label or _ for no argument label

Delegation

• design pattern: method or way of organizing a program/application’s code in a way that is commonplace, repeatable and practically sound (over time)
• delegation: situation where class (delegator) delegates behavioural logic to another class (delegate)
  • separation of responsibilities and concerns
  • often used as a way for one class to communicate with another
  • one class delegates the opportunity for an action to be carried out to another class due to a lifecycle event that will or did happen
  • NSNotificationCenter is for broadcasting to multiple listening instances whereas delegation is for one