[Swift] Conditional Statements

※ if Statements

if condition {
    code
}

if condition {
    statements
} else {
    statements
}

여기서 condition 은 Bool 값이다. (true, false)

- if

var temperatureInFaherenheit = 30

if temperatureInFaherenheit <= 32 {
    print("It's very cold. Consider wearing a scarf.")
}

- if - else

temperatureInFaherenheit = 90

if temperatureInFahereheit <= 32 {
    print("It's very cold. Consider Wearing a sarf.")
}else {
    print("It's not that cold. Wear a t-shirt")
}

- if - else if - else

temperatureInFaherenheit = 90

if temperatureInFahereheit <= 32 {
    print("It's very cold. Consider Wearing a scarf.")
} else if temperatureInFahereheit >= 86 {
    print("It's really warm. Don't forget to wear sunscreen.")
} else {
    print("It's not that cold. Wear a t-shirt")
}

- if - else if

temperatureInFaherenheit = 72

if temperatureInFahereheit <= 32 {
    print("It's very cold. Consider Wearing a scarf.")
} else if temperatureInFahereheit >= 86 {
    print("It's really warm. Don't forget to wear sunscreen.")
}

- Logical And Operator

아래 두 if문은 동일하다.

if (temperatureInFahrenheit > 0) && (temperatureInFahrenheit % 2 == 0) {
}

if temperatureInFahrenheit > 0, temperatureInFahrenheit % 2 ==0 {
}

※ switch Statements

switch value {
case value 1:
    respond to value 1
case value 2,
     value 3:
    respond to value 2 or 3
default:
    otherwise, do something else
}

switch 문은 가능한 모든 사례를 반드시 다루어야 한다.

- Interval Matching

let approximateCount = 30

switch approximateCount {
case 0...50:
    print("0 ~ 50")
case 51...100:
    print("51 ~ 100")
default:
    print("Something else")
}

- Compound cases

let someCharacter: Character = "e"

switch someCharacter {
case "a", "e", "i", "o", "u":
    print("\(someCharacter) is a vowel")
case "b", "c", "d", "f", "g", "h", "j", "k", "l", "m", "n", "p", "q", "r", "s", "t", "v", "w", "x", "y", "z":
    print("\(someCharacter) is a consonant")
default:
    print("\(someCharacter) is not a vowel or a consonant")
}

※ Early Exit

- guard Statements

func update(age: Int) {
    guard 0...100 ~= age else { return }
    print("Pass")
}

update(age: 2)
update(age: -1)
update(age: 100)