Data Types

• Int, Float, Double, String

There are no implicit conversions between types.

Integer to string:

let a = 3
let b = "a is " + String(a)

String interpolation, use \(value). value can be an expression:: To get a lowercased string, use the method .lowercased() of a string variable.

let s = 10 let s2 = "s is (s)"

Array of string:

var arr = [1, 2, 3]
# The type of arr is [Int]

# to append a new value to arr
arr.append(10)

# to make it empty
arr = []

# Create an empty array
var arr2: [Int] = []

Dictionary (string to int):

var d = ["one": 1, "two": 2]

# type of d is [String: Int]

# make d empty
d = [:]

# create an empty dict that maps string to int
var d2: [String: Int] = [:]

To iterate an array:

let values = [1, 2, 3]
var s = 0
for i in values {
  s += i
}
print(s)
# s is 6

For loop (1):

var k = 0
for i in 0..<4 {
  k += i
}
print(k)
# k is 6
# note: 0..<4 produces 0, 1, 2, 3
# 4 is not included

For loop (2):

var k = 0
for i in 0...4 {
  k += i
}
print(k)
# k is 10
# note: 0...4 produces 0, 1, 2, 3, 4
# 4 is included

Optional types:

var i: Int? = 1
print(i == nil) // false

// if i is not nil, then assign i to b
// if i is nil, then assign 10 to b
//
var b = i ?? 10
print(b) // b is 1

i = nil
b = i ?? 10
print(b) // b is 10