這句代碼已經(jīng)是一個(gè)完整的程序了
print("Hello World")
let 聲明恒量 編譯期不需要知道類(lèi)型件炉，但是必須正確的賦值
var 聲明變量
自動(dòng)類(lèi)型推斷這個(gè)恒量的類(lèi)型毁枯，另外，也在冒號(hào)后面指定類(lèi)型
let implicitFloat:Float = 4
print(implicitFloat)
不能含蓄的進(jìn)行類(lèi)型轉(zhuǎn)換船逮，需要明確的指定類(lèi)型
let label = "the width is "
let width = 94
let labelWidth = label + String(width)
print(labelWidth)
拼接不同類(lèi)型的變量
let oldFloat = 4.0
let Jack = "Jack"
let jackOld = "jack is \(oldFloat) years old"
print(jackOld)
""" 連續(xù)的三個(gè)雙引號(hào)表示換行
let apples = 3
let oranges = 5
let quotation = """
I said "I have \(apples) apples."
And then I said "I have \(apples + oranges) pieces of fruit."
"""
print(quotation)
使用圓括號(hào)和方括號(hào)創(chuàng)建數(shù)組和字典([])丹禀，使用索引獲取或者賦值，允許子啊末尾添加一個(gè)逗號(hào)
var shoppingList = ["catfish", "water", "tulips", "blue paint"]
print(shoppingList) ["catfish", "water", "tulips", "blue paint"]
shoppingList[1] = "bottle of water"
print(shoppingList) ["catfish", "bottle of water", "tulips", "blue paint"]
var occupations = [
"Malcolm": "Captain",
"Kaylee": "Mechanic",
]
occupations["Jayne"] = "Public Relations"
print(occupations)
初始化空的數(shù)組和字典危融，需要使用初始化格式
let emptyArrar = [String]()
let emptyDic = [String: Float]()
如果消息可以推斷出來(lái)畏铆，就不用指定類(lèi)型了, 比如，給新變量賦值吉殃，或者函數(shù)傳參
shoppingList = []
occupations = [:]
print(shoppingList)
print(occupations)
