Swift 數(shù)組用于存儲相同類型的值的順序列表。Swift 要嚴(yán)格檢查,它不允許錯誤地在數(shù)組中存放了錯誤的類型。
如果賦值創(chuàng)建數(shù)組到一個變量,它總是可變的,這意味著可以通過添加元素來改變它, 刪除或更改其項目,但如果分配一個數(shù)組常量到則該數(shù)組,則數(shù)組是不可被改變的, 也就它的大小和內(nèi)容不能被改變。
可以使用下面的初始化程序語法來創(chuàng)建某種類型的空數(shù)組:
var someArray = [SomeType]()
下面是創(chuàng)建一個給定的大小,并用初始值的數(shù)組的語法:
var someArray = [SomeType](count: NumbeOfElements, repeatedValue: InitialValue)
下面是一個例子,以創(chuàng)建具有3個元素并初始值為零的 int 類型空數(shù)組:
var someInts = [Int](count: 3, repeatedValue: 0)
下面是一個創(chuàng)建三個元素的數(shù)組,并指定三個值的數(shù)組的例子:
var someInts:[Int] = [10, 20, 30]
可以使用下標(biāo)語法從數(shù)組中檢索對應(yīng)值,傳遞數(shù)組名后方括號內(nèi)的索引對應(yīng)的值,如下:
var someVar = someArray[index]
在這里,指數(shù)從0開始,這意味著可以使用索引0來訪問第一個元素,第二元素可以通過使用索引1進(jìn)行訪問,其它類似。讓我們來看看下面創(chuàng)建,初始化和訪問數(shù)組的例子:
import Cocoa var someInts = [Int](count: 3, repeatedValue: 10) var someVar = someInts[0] println( "Value of first element is \(someVar)" ) println( "Value of second element is \(someInts[1])" ) println( "Value of third element is \(someInts[2])" )
當(dāng)上述代碼被編譯和執(zhí)行時,它產(chǎn)生了以下結(jié)果:
Value of first element is 10 Value of second element is 10 Value of third element is 10
可以使用 append() 方法或加法賦值運(yùn)算符(+=)將新的項目添加到數(shù)組的末尾,在這里首先創(chuàng)建一個空的數(shù)組,然后添加新的元素到數(shù)組中,如下圖所示:
import Cocoa var someInts = [Int]() someInts.append(20) someInts.append(30) someInts += [40] var someVar = someInts[0] println( "Value of first element is \(someVar)" ) println( "Value of second element is \(someInts[1])" ) println( "Value of third element is \(someInts[2])" )
當(dāng)上述代碼被編譯和執(zhí)行時,它產(chǎn)生了以下結(jié)果:
Value of first element is 20 Value of second element is 30 Value of third element is 40
可以通過分配一個在給定的索引處新的值修改數(shù)組的現(xiàn)有元素,如在下面的例子:
import Cocoa var someInts = [Int]() someInts.append(20) someInts.append(30) someInts += [40] // Modify last element someInts[2] = 50 var someVar = someInts[0] println( "Value of first element is \(someVar)" ) println( "Value of second element is \(someInts[1])" ) println( "Value of third element is \(someInts[2])" )
當(dāng)上述代碼被編譯和執(zhí)行時,它產(chǎn)生了以下結(jié)果:
Value of first element is 20 Value of second element is 30 Value of third element is 50
可以使用 for-in 循環(huán)迭代級數(shù),在下面的例子是數(shù)組的整個集值,如下圖所示:
import Cocoa var someStrs = [String]() someStrs.append("Apple") someStrs.append("Amazon") someStrs += ["Google"] for item in someStrs { println(item) }
當(dāng)上述代碼被編譯和執(zhí)行時,它產(chǎn)生了以下結(jié)果:
Apple Amazon Google
也可以使用 enumerate() 函數(shù),如下面的例子所示,它返回索引及對應(yīng)的值:
import Cocoa var someStrs = [String]() someStrs.append("Apple") someStrs.append("Amazon") someStrs += ["Google"] for (index, item) in enumerate(someStrs) { println("Value at index = \(index) is \(item)") }
當(dāng)上述代碼被編譯和執(zhí)行時,它產(chǎn)生了以下結(jié)果:
Value at index = 0 is Apple Value at index = 1 is Amazon Value at index = 2 is Google
使用加法運(yùn)算符(+),以添加的相同類型的數(shù)組,這將產(chǎn)生新的數(shù)組是來自兩個數(shù)組值相加組合后的數(shù)組,如下:
import Cocoa var intsA = [Int](count:2, repeatedValue: 2) var intsB = [Int](count:3, repeatedValue: 1) var intsC = intsA + intsB for item in intsC { println(item) }
當(dāng)上述代碼被編譯和執(zhí)行時,它產(chǎn)生了以下結(jié)果:
2 2 1 1 1
可以使用只讀計算 (count) 數(shù)組屬性,找出下面顯示出數(shù)組中元素的個數(shù):
import Cocoa var intsA = [Int](count:2, repeatedValue: 2) var intsB = [Int](count:3, repeatedValue: 1) var intsC = intsA + intsB println("Total items in intsA = \(intsA.count)") println("Total items in intsB = \(intsB.count)") println("Total items in intsC = \(intsC.count)")
當(dāng)上述代碼被編譯和執(zhí)行時,它產(chǎn)生了以下結(jié)果:
Total items in intsA = 2 Total items in intsB = 3 Total items in intsC = 5
使用只讀數(shù)組的空屬性(isEmpty)找出一個數(shù)組是否為空,如下圖所示:
import Cocoa var intsA = [Int](count:2, repeatedValue: 2) var intsB = [Int](count:3, repeatedValue: 1) var intsC = [Int]() println("intsA.isEmpty = \(intsA.isEmpty)") println("intsB.isEmpty = \(intsB.isEmpty)") println("intsC.isEmpty = \(intsC.isEmpty)")
當(dāng)上述代碼被編譯和執(zhí)行時,它產(chǎn)生了以下結(jié)果:
intsA.isEmpty = false intsB.isEmpty = false intsC.isEmpty = true