Swift Flashcards
Declare implicitly as type Int: var year = 2015
2015
unknownString = 3
3 is NSObject
unknownString = “3”
“3”
If you know that the value of a variable won’t change again, you should use let. Here, myName is declared as a constant and initialized with the value Jesse: let myName = “Jesse”
“Jesse”
Declare as optional (i.e. empty): var height: Int? friend = nil
nil nil
To assign an optional an initial value: var friend: String? = “Joe”
“Joe”
To check if there’s a vale for or optional:if let someone = friend{ print(“Hello ” + someone)}
“Hello Joe”
var b = a * 3
15
var c = b/2
2
var c: Double = 5/2
2.5
c * 2
5
c * [integer 4]
10
c * Double(int)
10
Tuples are combined values that always appear together. Let person = (“Joe”, 24) print(person.0) print(person.1)
Joe 24
Often we want to refer to members in a tuple by name rather than index value (e.g. .0, .1, .2, etc.). let (name, age) = person print(name)
Joe
Tuple values may be named at the time of creation let person = (name: “Joe”, age: 24) print(person.name)
Joe
Arrays are defined with brackets and commas: var arr = [1, 2, 3, 4, 5] arr = [0]
1
arr.append(6) print(arr)
[1, 2, 3, 4, 5, 6]
arr.removeAtIndex(2) print(arr)
[1, 2, 4, 5, 6]
arr.removeLast() print(arr)
[1, 2, 4, 5]
Ranges are indicated with ellipsis and their counts also begin at zero. arr.removeRange(1…2) print(arr)
[1, 5]
var dict = [“name”: “Rob”, “age”: 34, “gender”: “male”] print(dict[“name”])
Optional(Rob)
Use ! to force unwrap: print(dict[“name”]!)
Rob
To add a value: dict[“hairColor”] = “brown”
{Some ‘brown’}
var name = dict[“name”] var myString = “my name is ” + name
name is an NSObject (non string object)
var myString = “my name is (name)”
“my name is Optional(Rob)”
Force Unwrap var myString = “my name is (name!)”
“my name is Rob”
for var i = 1; i
9 times
var arr = [8, 3, 9, 91] for (index, value) in arr.enumerate() { arr[index] = value + 1 } print(arr)
[8, 3 , 9, 91] (4 times) [9, 4, 10, 92]/n
var i = 1 while i
5 10 15 20 25 30 35 40 45 50
