欧美bbbwbbbw肥妇,免费乱码人妻系列日韩,一级黄片

Swift編程中的一些類型轉(zhuǎn)換方法詳解

 更新時間：2015年11月07日 18:14:11   投稿：goldensun  
這篇文章主要介紹了Swift編程中的一些類型轉(zhuǎn)換方法詳解,是Swift入門學(xué)習(xí)中的基礎(chǔ)知識,需要的朋友可以參考下

驗證一個實例的類型'類型轉(zhuǎn)換'在 Swift 語言編程中。它是用來檢查實例類型是否屬于特定超類或子類或其自己的層次結(jié)構(gòu)定義。

Swift 類型轉(zhuǎn)換提供兩個操作符：“is” 檢查值的類型和 'as' 將類型值轉(zhuǎn)換為不同的類型值。 類型轉(zhuǎn)換還檢查實例類型是否符合特定的協(xié)議一致性標(biāo)準(zhǔn)。

定義一個類層次結(jié)構(gòu)
類型轉(zhuǎn)換用于檢查實例的類型或者它屬于特定類型。此外，檢查類和它的子類層次結(jié)構(gòu)來檢查并轉(zhuǎn)換這些實例，使之作為一個相同的層次結(jié)構(gòu)。

復(fù)制代碼 代碼如下:

class Subjects {
   var physics: String
   init(physics: String) {
      self.physics = physics
   }
}

class Chemistry: Subjects {
   var equations: String
   init(physics: String, equations: String) {
      self.equations = equations
      super.init(physics: physics)
   }
}

class Maths: Subjects {
   var formulae: String
   init(physics: String, formulae: String) {
      self.formulae = formulae
      super.init(physics: physics)
   }
}

let sa = [
   Chemistry(physics: "solid physics", equations: "Hertz"),
   Maths(physics: "Fluid Dynamics", formulae: "Giga Hertz")]


let samplechem = Chemistry(physics: "solid physics", equations: "Hertz")
println("Instance physics is: \(samplechem.physics)")
println("Instance equation is: \(samplechem.equations)")


let samplemaths = Maths(physics: "Fluid Dynamics", formulae: "Giga Hertz")
println("Instance physics is: \(samplemaths.physics)")
println("Instance formulae is: \(samplemaths.formulae)")


當(dāng)我們使用 playground 運行上面的程序，得到以下結(jié)果。

Instance physics is: solid physics
Instance equation is: Hertz
Instance physics is: Fluid Dynamics
Instance formulae is: Giga Hertz

類型檢查
進行類型檢查，用 'is' 操作符。在 'is' 操作符檢查類型實例是否屬于特定的子類型，如果它屬于該實例返回“true”，否則將返回“false”。

復(fù)制代碼 代碼如下:

class Subjects {
   var physics: String
   init(physics: String) {
      self.physics = physics
   }
}

class Chemistry: Subjects {
   var equations: String
   init(physics: String, equations: String) {
      self.equations = equations
      super.init(physics: physics)
   }
}

class Maths: Subjects {
   var formulae: String
   init(physics: String, formulae: String) {
      self.formulae = formulae
      super.init(physics: physics)
   }
}

let sa = [
   Chemistry(physics: "solid physics", equations: "Hertz"),
   Maths(physics: "Fluid Dynamics", formulae: "Giga Hertz"),
   Chemistry(physics: "Thermo physics", equations: "Decibels"),
   Maths(physics: "Astro Physics", formulae: "MegaHertz"),
   Maths(physics: "Differential Equations", formulae: "Cosine Series")]


let samplechem = Chemistry(physics: "solid physics", equations: "Hertz")
println("Instance physics is: \(samplechem.physics)")
println("Instance equation is: \(samplechem.equations)")


let samplemaths = Maths(physics: "Fluid Dynamics", formulae: "Giga Hertz")
println("Instance physics is: \(samplemaths.physics)")
println("Instance formulae is: \(samplemaths.formulae)")

var chemCount = 0
var mathsCount = 0
for item in sa {
   if item is Chemistry {
      ++chemCount
   } else if item is Maths {
      ++mathsCount
   }
}

println("Subjects in chemistry contains \(chemCount) topics and maths contains \(mathsCount) topics")


當(dāng)我們使用 playground 運行上面的程序，得到以下結(jié)果。

Instance physics is: solid physics
Instance equation is: Hertz
Instance physics is: Fluid Dynamics
Instance formulae is: Giga Hertz
Subjects in chemistry contains 2 topics and maths contains 3 topics

向下轉(zhuǎn)換
向下類型轉(zhuǎn)換的子類型可以有兩個操作符（如：as? 和 as!）。as? 當(dāng)值是nil，返回一個可選值。它是用來檢查成功向下轉(zhuǎn)型。

“as!” 返回強制解包裹，如可選鏈，向下轉(zhuǎn)換返回 nil 值。它用來觸發(fā)運行時錯誤在向下轉(zhuǎn)型出現(xiàn)故障時

復(fù)制代碼 代碼如下:

class Subjects {
   var physics: String
   init(physics: String) {
      self.physics = physics
   }
}

class Chemistry: Subjects {
   var equations: String
   init(physics: String, equations: String) {
      self.equations = equations
      super.init(physics: physics)
   }
}

class Maths: Subjects {
   var formulae: String
   init(physics: String, formulae: String) {
      self.formulae = formulae
      super.init(physics: physics)
   }
}

let sa = [
   Chemistry(physics: "solid physics", equations: "Hertz"),
   Maths(physics: "Fluid Dynamics", formulae: "Giga Hertz"),
   Chemistry(physics: "Thermo physics", equations: "Decibels"),
   Maths(physics: "Astro Physics", formulae: "MegaHertz"),
   Maths(physics: "Differential Equations", formulae: "Cosine Series")]


let samplechem = Chemistry(physics: "solid physics", equations: "Hertz")
println("Instance physics is: \(samplechem.physics)")
println("Instance equation is: \(samplechem.equations)")


let samplemaths = Maths(physics: "Fluid Dynamics", formulae: "Giga Hertz")
println("Instance physics is: \(samplemaths.physics)")
println("Instance formulae is: \(samplemaths.formulae)")

var chemCount = 0
var mathsCount = 0

for item in sa {
   if let print = item as? Chemistry {
      println("Chemistry topics are: '\(print.physics)', \(print.equations)")
   } else if let example = item as? Maths {
      println("Maths topics are: '\(example.physics)',  \(example.formulae)")
   }
}


當(dāng)我們使用 playground 運行上面的程序，得到以下結(jié)果。

Instance physics is: solid physics
Instance equation is: Hertz
Instance physics is: Fluid Dynamics
Instance formulae is: Giga Hertz
Chemistry topics are: 'solid physics', Hertz
Maths topics are: 'Fluid Dynamics', Giga Hertz
Chemistry topics are: 'Thermo physics', Decibels
Maths topics are: 'Astro Physics', MegaHertz
Maths topics are: 'Differential Equations', Cosine Series

類型轉(zhuǎn)換：任何與任何對象
為了表示實例屬于任何類型包括函數(shù)類型，使用“Any”關(guān)鍵字

復(fù)制代碼 代碼如下:

class Subjects {
   var physics: String
   init(physics: String) {
      self.physics = physics
   }
}

class Chemistry: Subjects {
   var equations: String
   init(physics: String, equations: String) {
      self.equations = equations
      super.init(physics: physics)
   }
}

class Maths: Subjects {
   var formulae: String
   init(physics: String, formulae: String) {
      self.formulae = formulae
      super.init(physics: physics)
   }
}

let sa = [
   Chemistry(physics: "solid physics", equations: "Hertz"),
   Maths(physics: "Fluid Dynamics", formulae: "Giga Hertz"),
   Chemistry(physics: "Thermo physics", equations: "Decibels"),
   Maths(physics: "Astro Physics", formulae: "MegaHertz"),
   Maths(physics: "Differential Equations", formulae: "Cosine Series")]


let samplechem = Chemistry(physics: "solid physics", equations: "Hertz")
println("Instance physics is: \(samplechem.physics)")
println("Instance equation is: \(samplechem.equations)")


let samplemaths = Maths(physics: "Fluid Dynamics", formulae: "Giga Hertz")
println("Instance physics is: \(samplemaths.physics)")
println("Instance formulae is: \(samplemaths.formulae)")

var chemCount = 0
var mathsCount = 0

for item in sa {
   if let print = item as? Chemistry {
      println("Chemistry topics are: '\(print.physics)', \(print.equations)")
   } else if let example = item as? Maths {
      println("Maths topics are: '\(example.physics)',  \(example.formulae)")
   }
}

var exampleany = [Any]()

exampleany.append(12)
exampleany.append(3.14159)
exampleany.append("Example for Any")
exampleany.append(Chemistry(physics: "solid physics", equations: "Hertz"))

for print in exampleany {
   switch print {
   case let someInt as Int:
      println("Integer value is \(someInt)")
   case let someDouble as Double where someDouble > 0:
      println("Pi value is \(someDouble)")
   case let someString as String:
      println("\(someString)")
   case let phy as Chemistry:
      println("Topics '\(phy.physics)', \(phy.equations)")
   default:
      println("None")
   }
}


當(dāng)我們使用 playground 運行上面的程序，得到以下結(jié)果。

Instance physics is: solid physics
Instance equation is: Hertz
Instance physics is: Fluid Dynamics
Instance formulae is: Giga Hertz
Chemistry topics are: 'solid physics', Hertz
Maths topics are: 'Fluid Dynamics', Giga Hertz
Chemistry topics are: 'Thermo physics', Decibels
Maths topics are: 'Astro Physics', MegaHertz
Maths topics are: 'Differential Equations', Cosine Series
Integer value is 12
Pi value is 3.14159
Example for Any
Topics 'solid physics', Hertz
AnyObject

為了表示是任何類型的類實例，使用AnyObject“關(guān)鍵字

復(fù)制代碼 代碼如下:

 class Subjects {
   var physics: String
   init(physics: String) {
      self.physics = physics
   }
}

class Chemistry: Subjects {
   var equations: String
   init(physics: String, equations: String) {
      self.equations = equations
      super.init(physics: physics)
   }
}

class Maths: Subjects {
   var formulae: String
   init(physics: String, formulae: String) {
      self.formulae = formulae
      super.init(physics: physics)
   }
}

let saprint: [AnyObject] = [Chemistry(physics: "solid physics", equations: "Hertz"),
   Maths(physics: "Fluid Dynamics", formulae: "Giga Hertz"),
   Chemistry(physics: "Thermo physics", equations: "Decibels"),
   Maths(physics: "Astro Physics", formulae: "MegaHertz"),
   Maths(physics: "Differential Equations", formulae: "Cosine Series")]


let samplechem = Chemistry(physics: "solid physics", equations: "Hertz")
println("Instance physics is: \(samplechem.physics)")
println("Instance equation is: \(samplechem.equations)")


let samplemaths = Maths(physics: "Fluid Dynamics", formulae: "Giga Hertz")
println("Instance physics is: \(samplemaths.physics)")
println("Instance formulae is: \(samplemaths.formulae)")

var chemCount = 0
var mathsCount = 0

for item in saprint {
   if let print = item as? Chemistry {
      println("Chemistry topics are: '\(print.physics)', \(print.equations)")
   } else if let example = item as? Maths {
      println("Maths topics are: '\(example.physics)',  \(example.formulae)")
   }
}

var exampleany = [Any]()
exampleany.append(12)
exampleany.append(3.14159)
exampleany.append("Example for Any")
exampleany.append(Chemistry(physics: "solid physics", equations: "Hertz"))

for print in exampleany {
   switch print {
   case let someInt as Int:
      println("Integer value is \(someInt)")
   case let someDouble as Double where someDouble > 0:
      println("Pi value is \(someDouble)")
   case let someString as String:
      println("\(someString)")
   case let phy as Chemistry:
      println("Topics '\(phy.physics)', \(phy.equations)")
   default:
      println("None")
   }
}


當(dāng)我們使用 playground 運行上面的程序，得到以下結(jié)果。

Instance physics is: solid physics
Instance equation is: Hertz
Instance physics is: Fluid Dynamics
Instance formulae is: Giga Hertz
Chemistry topics are: 'solid physics', Hertz
Maths topics are: 'Fluid Dynamics', Giga Hertz
Chemistry topics are: 'Thermo physics', Decibels
Maths topics are: 'Astro Physics', MegaHertz
Maths topics are: 'Differential Equations', Cosine Series
Integer value is 12
Pi value is 3.14159
Example for Any
Topics 'solid physics', Hertz

相關(guān)文章

  • Switch語句的技巧

    Switch語句的技巧

    switch語句對一個表達式求值，將結(jié)果與 case 子語句比較，如果匹配，則從 case 處的語句向下執(zhí)行，本文給大家介紹Switch語句的技巧，需要的朋友參考下吧
    2016-02-02
  • swift版webview加載網(wǎng)頁進度條效果

    swift版webview加載網(wǎng)頁進度條效果

    這篇文章主要為大家詳細(xì)介紹了swift實現(xiàn)webview加載網(wǎng)頁進度條效果，具有一定的參考價值，感興趣的小伙伴們可以參考一下
    2017-11-11
  • 分析Swift性能高效的原因

    分析Swift性能高效的原因

    絕大多數(shù)公司選擇Swift語言開發(fā)iOS應(yīng)用，主要原因是因為Swift相比Objc有更快的運行效率，更加安全的類型檢測，更多現(xiàn)代語言的特性提升開發(fā)效率；這一系列的優(yōu)點使Swift語言的熱度越來越高。
    2020-10-10
  • swift表格控件使用方法詳解(UITableview)

    swift表格控件使用方法詳解(UITableview)

    這篇文章主要為大家詳細(xì)介紹了swift表格控件的使用方法，文中示例代碼介紹的非常詳細(xì)，具有一定的參考價值，感興趣的小伙伴們可以參考一下
    2022-01-01
  • 簡單理解插入排序算法及Swift版的代碼示例

    簡單理解插入排序算法及Swift版的代碼示例

    插入排序算法可以在已排序的序列中將要插入的元素和原有元素保持有序,這里我們來簡單理解插入排序算法及Swift版的代碼示例,需要的朋友可以參考下
    2016-07-07
  • Objective-c代碼如何移植為Swift代碼 Objective-c代碼轉(zhuǎn)移到Swift過程介紹

    Objective-c代碼如何移植為Swift代碼 Objective-c代碼轉(zhuǎn)移到Swift過程介紹

    這篇文章主要介紹了Objective-c代碼如何移植為Swift代碼,Objective-c代碼轉(zhuǎn)移到Swift過程介紹,需要的朋友可以參考下
    2014-07-07
  • Swift快速集成下拉刷新和上拉加載更多示例代碼

    Swift快速集成下拉刷新和上拉加載更多示例代碼

    這篇文章主要介紹了Swift快速集成下拉刷新和上拉加載更多示例代碼，具有一定的參考價值，感興趣的小伙伴們可以參考一下
    2017-05-05
  • Swift方法調(diào)度之類的普通方法底層探究

    Swift方法調(diào)度之類的普通方法底層探究

    這篇文章主要介紹了Swift-方法調(diào)度-類的普通方法底層探究,本文給大家介紹的非常詳細(xì)，對大家的學(xué)習(xí)或工作具有一定的參考借鑒價值，需要的朋友可以參考下
    2021-11-11
  • Swift 3.0基礎(chǔ)學(xué)習(xí)之枚舉類型

    Swift 3.0基礎(chǔ)學(xué)習(xí)之枚舉類型

    枚舉在編程中很多時候要用到，在 Swift 中，枚舉具有更多的特性。下面這篇文章主要介紹了Swift 3.0基礎(chǔ)學(xué)習(xí)之枚舉類型的相關(guān)資料，文中介紹的非常詳細(xì)，需要的朋友可以參考借鑒，下面來一起看看吧。
    2017-03-03
  • 通過示例分析Swift單例模式

    通過示例分析Swift單例模式

    這篇文章主要介紹了通過示例分析Swift單例模式的三種方法，分別是全局變量，內(nèi)部變量，dispatch_once方式，有需要的小伙伴可以參考下。
    2015-06-06

最新評論