十節(jié)結(jié)構(gòu)體與類

iOS結(jié)構(gòu)體與類Swift語言基礎(chǔ)結(jié)構(gòu)體與類定義1通過class和struct來聲明類和結(jié)構(gòu)體，大括號(hào)里定義它們的內(nèi)容classSomeClass{//classdefinitiongoeshere}structSomeStructure{//structuredefinitiongoeshere}structResolution{varwidth=0varheight=0}classVideoMode{varresolution=Resolution()varinterlaced=falsevarframeRate=0.0varname:String?}結(jié)構(gòu)體與類結(jié)構(gòu)體與類的實(shí)例2使用初始化方法來生成新的實(shí)例letsomeResolution=Resolution()letsomeVideoMode=VideoMode()結(jié)構(gòu)體與類訪問屬性3使用點(diǎn)語法訪問類和結(jié)構(gòu)體的屬性，或者子屬性println(“ThewidthofsomeResolutionis\(someResolution.width)”)//prints“ThewidthofsomeResolutionis0”println(“ThewidthofsomeVideoModeis\(someVideoMode.resolution.width)”)//prints“ThewidthofsomeVideoModeis0”someVideoMode.resolution.width=1280println(“ThewidthofsomeVideoModeisnow\(someVideoMode.resolution.width)”)//prints"ThewidthofsomeVideoModeisnow1280"結(jié)構(gòu)體與類結(jié)構(gòu)體類型的初始化方法4所有結(jié)構(gòu)體都有一個(gè)自動(dòng)生成的初始化方法，用于初始化結(jié)構(gòu)體中成員的屬性letvga=Resolution(width:640,height:480)結(jié)構(gòu)體與類結(jié)構(gòu)體和枚舉都是值類型的5值類型在賦值給變量、常量或者傳入到一個(gè)函數(shù)的時(shí)候，操作的都是值的拷貝，意味著它們的實(shí)例以及實(shí)例所包含的屬性在代碼傳值的時(shí)候都會(huì)被復(fù)制lethd=Resolution(width:1920,height:1080)varhd2=hdhd2.width=2048println(“hd2isnow\(hd2.width)pixelswide”)//prints“hd2isnow2048pixelswide”println("hdisstill\(hd.width)pixelswide")//prints"hdisstill1920pixelswide"結(jié)構(gòu)體與類結(jié)構(gòu)體和枚舉都是值類型的5枚舉也一樣enumCompassPoint{caseNorth,South,East,West}varcurrentDirection=CompassPoint.WestletrememberedDirection=currentDirectioncurrentDirection=.EastifrememberedDirection==.West{println(“Theremembereddirectionisstill.West”)}//prints"Theremembereddirectionisstill.West"結(jié)構(gòu)體與類類是引用類型6letvm1=VideoMode()vm1.resolution=hdvm1.frameRate=25.0varvm2=vm1vm2.frameRate=30.0println(“TheframeRatepropertyofvm1isnow\(vm1.frameRate)”)//prints“TheframeRatepropertyofvm1isnow30.0"結(jié)構(gòu)體和類恒等運(yùn)算符7因?yàn)轭愂且妙愋停赡艹霈F(xiàn)多個(gè)變量在引用同一個(gè)類實(shí)例的情況，所以Swift提供了兩個(gè)恒等運(yùn)算符，判斷兩個(gè)常量或者變量是否引用同一個(gè)類實(shí)例等價(jià)于(===)表示兩個(gè)類類型的常量或變量引用同一個(gè)實(shí)例不等價(jià)(!==)ifvm1===vm2{println(“vm1andvm2refertothesameResolutioninstance.”)}//prints”vm1andvm2refertothesameResolutioninstance."結(jié)構(gòu)體和類結(jié)構(gòu)體和類的選擇8結(jié)構(gòu)體：值傳遞主要用來封