[Swift]基礎練習2

參考網站

• http://bone.twbbs.org.tw/blog/2397.html
• http://tommy60703.gitbooks.io/swift-language-traditional-chinese/

/*
 * 練習For迴圈與IF判斷
 */
let individualScores = [75,43,103,87,12]
var teamScore = 0
for score  in individualScores {
    if score > 50 {
        teamScore += 3
    }else {
        teamScore += 1
    }
}
teamScore

/*
 * 複合值Tuples練習
 */
let http404Error = (404, "Not Found")
let (statusCode, statusMessage) = http404Error
println("The status code is \(statusCode)")
println("The status message is \(statusMessage)")

/*
 * 複合值Tuples練習二
 */
let http200Status = (statusCode: 200, description: "OK")
println("The status code is \(http200Status.statusCode)")
println("The status message is \(http200Status.description)")

/*
 * 型別轉換
 */
let possibleNumber = "123" //當入123型別可以正常轉換，但是輸入Hello會傳回nil
let convertedNumber = possibleNumber.toInt()
// convertedNumber 被推測為型別 "Int?"， 或者型別 "optional Int"
if convertedNumber == 123 {
    println("\(possibleNumber) has an integer value of \(convertedNumber!)")
} else {
    println("\(possibleNumber) could not be converted to an integer")
}

/*
 * 隱式解析 Optionals
 */
let possibleString: String? = "An optional string."
println(possibleString!) // 需要驚嘆號來獲取值

let assumedString: String! = "An implicitly unwrapped optional string."
println(assumedString)  // 不需要感嘆號

/*
 * 除錯用
 */
let age = -3
assert(age >= 0, "A person's age cannot be less than zero")
// 因為 age < 0，所以assertion會觸發

/*
 * 運算元練習
 */
var i = 10
var x = 0
x = i++    //LOAD  i (現在暫存器上的值是 10)
              // STORE x (所以現在 x = 10，暫存器還是 10)
              // ADD   1 (現在暫存器上的值是 11)
              // STORE i (現在 i = 11)
var j = 10
var y = 0
y = ++j   // LOAD  j (現在暫存器上的值是 10)
             // ADD   1 (現在暫存器上的值是 11)
             // STORE j (現在 j = 11)
             // STORE y (現在 y = 11)
println("x = \(x)");  // x = 10
println("y = \(y)");  // y = 11