02 The Swift Language.md

# SWIFT TOUR
- implicit variables and immutable variables
- explicit variables
- values need to be explicitly converted
- use \() to convert a variable to a string (in quotes)

- arrays and dictionaries


## To Do

- implicit and explicit variable data types
- strings
- string interpolation \()
- chars (converting string to array of chars).
- arrays
- introspection (type)
- enumerated
- characters
- repeat while
- conditional (if)
- optionals
- exit (quit script with exit code)

## Membership

- enumerations (errors)
- exception handling & throwing errors
- guard let else
- switch
- type of

## Contact

- declaring functions
- return types
- unused vars `_`
- functions that throw errors

-----

## Arrays

```swift
let colours:[String] = ["red", "orange", "green"]
print(colours.count)
print("\(colours)")

var shoppingList = [String]()
//shoppingList.append("bread")
shoppingList += ["Bread"]
shoppingList.append("butter")
print("\(shoppingList)")
for item in shoppingList {
  print("\(item)")
}
```

## Dictionaries
```swift
var book   = [
  "isbn": "1491943122",
  "title": "Learning Node"
]

var ages = [String:Int]()
ages["john"] = 42
ages["jane"] = 24
print("\(ages)")
for (name, age) in ages {
  print("\(name) is \(age) years old")
}
```

struct

// normally functions use their parameter names as labels so you need to have a custom argument label before each parameter name.
```swift
func printPerson(withName name:String, andAge age:Int) {
  print("\(name) is \(age) years old")
}

printPerson(withName: "frank", andAge: 64)

// use _ if you want to omit the first argument label.
func add(_ num1:Int, and num2:Int) -> Int {
  return num1 + num2
}

print(add(24, and: 42))
```

## OOP

- objects and classes
- importing from separate file
- create instance by putting parenthesis before class name.
- private instance variables
- properties (getters and setters)
- methods
- static 


## Async

- closures (callbacks)


## Foundation Framework

## Unit Testing

- importing XCUnit