Swift 类和结构体(八)

1.定义

2.类和结构体的实例

letsomeResolution=Resolution()
1. letsomeVideoMode=VideoMode()

3.访问属性

println("ThewidthofsomeResolutionis(someResolution.width)")
1. //prints"ThewidthofsomeResolutionis0"
2. println("ThewidthofsomeVideoModeis(someVideoMode.resolution.width)")
3. //prints"ThewidthofsomeVideoModeis0"
4. someVideoMode.resolution.width=1280
5. println("ThewidthofsomeVideoModeisnow(someVideoMode.resolution.width)")
6. //prints"ThewidthofsomeVideoModeisnow1280"

4.结构体类型的初始化方法

letvga=Resolution(width:640,height:480)

5.结构体和枚举都是值类型的

//以下定义一个hd常量，值为(1920,1080)像素的Resolution实例，然后定义cinema变量，其值为hd，cinema的值其实是hd得拷贝副本而不是hd本身，它们是两个不同的实例
1. lethd=Resolution(width:1920,0); background-color:inherit">height:1080)
2. varcinema=hd
3. //将cinema的width属性改变，而hd实例的中不会改变，两者的修改并不会相互影响对方，因为hd赋值给cinema的时候，实际是将hd存储的值进行拷贝，然后将拷贝的值存入cinema中
4. cinema.width=2048
5. println("cinemaisnow(cinema.width)pixelswide")
6. //prints"cinemaisnow2048pixelswide"
7. println("hdisstill(hd.width)pixelswide")
8. //prints"hdisstill1920pixelswide"

enumCompassPoint{
1. caseNorth,South,East,West
2. varcurrentDirection=CompassPoint.West
3. letrememberedDirection=currentDirection
4. currentDirection=.East
5. ifrememberedDirection==.West{
6. println("Theremembereddirectionisstill.West")
7. //prints"Theremembereddirectionisstill.West"

6.类是引用类型

lettenEighty=VideoMode()
1. tenEighty.resolution=hd
2. tenEighty.interlaced=true
3. tenEighty.name="1080i"
4. tenEighty.frameRate=25.0
5. letalsoTenEighty=tenEighty
6. alsoTenEighty.frameRate=30.0
7. println("TheframeRatepropertyoftenEightyisnow(tenEighty.frameRate)")
8. //prints"TheframeRatepropertyoftenEightyisnow30.0"

7.恒等运算符

iftenEighty===alsoTenEighty{
1. println("tenEightyandalsoTenEightyrefertothesameResolutioninstance.")
2. //prints"tenEightyandalsoTenEightyrefertothesameResolutioninstance."

8.类和结构体的选择

9.集合类型的赋值和拷贝行为

//以下字典key/value分别是String/Int，都是值类型，字典被拷贝时，两者都被拷贝
1. varages=["Peter":23,"Wei":35,"Anish":65,"Katya":19]
2. varcopiedAges=ages
3. copiedAges["Peter"]=24
4. println(ages["Peter"])
5. //prints"23"

//将整数(Int)数组赋值给a，b，c变量
1. vara=[1,2,0); background-color:inherit">3]
2. varb=a
3. varc=a
4. println(a[0])
5. //1
6. println(b[0])
7. println(c[0])
8. a[0]=42
9. //42
10. //当长度发生变化，Swift会创建这个数组的拷贝，a将会是原数组的一个独立拷贝
11. a.append(4)
12. a[0]=777
13. //777
14. //42

10.确保数组的唯一性

b.unshare()
1. b[0]=-105
2. println(a[0])
3. //777
4. println(b[0])
5. //-105
6. println(c[0])
7. //42

11.判断两个数组是否共用相同元素

ifb===c{
1. println("bandcstillsharethesamearrayelements.")
2. }else{
3. println("bandcnowrefertotwoindependentsetsofarrayelements.")
4. //prints"bandcnowrefertotwoindependentsetsofarrayelements."

ifb[0...1]===b[0...1]{
1. println("Thesetwosubarrayssharethesameelements.")
2. println("Thesetwosubarraysdonotsharethesameelements.")
3. //prints"Thesetwosubarrayssharethesameelements."

12.强制复制数组

varnames=["Mohsen","Hilary","Justyn","Amy","Rich","Graham","Vic"]
1. varcopiedNames=names.copy()
2. copiedNames[0]="Mo"
3. println(names[0])
4. //prints"Mohsen"

（编辑：李大同）

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