Swift編程中的一些類型轉換辦法詳解。本站提示廣大學習愛好者：（Swift編程中的一些類型轉換辦法詳解）文章只能為提供參考，不一定能成為您想要的結果。以下是Swift編程中的一些類型轉換辦法詳解正文
驗證一個實例的類型'類型轉換'在 Swift 說話編程中。它是用來檢討實例類型能否屬於特定超類或子類或其本身的條理構造界說。
Swift 類型轉換供給兩個操作符：“is” 檢討值的類型和 'as' 將類型值轉換為分歧的類型值。 類型轉換還檢討實例類型能否相符特定的協定分歧性尺度。
界說一個類條理構造
類型轉換用於檢討實例的類型或許它屬於特定類型。另外，檢討類和它的子類條理構造來檢討並轉換這些實例，使之作為一個雷同的條理構造。
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)")
當我們應用 playground 運轉下面的法式，獲得以下成果。
Instance physics is: solid physics Instance equation is: Hertz Instance physics is: Fluid Dynamics Instance formulae is: Giga Hertz
類型檢討
停止類型檢討，用 'is' 操作符。在 'is' 操作符檢討類型實例能否屬於特定的子類型，假如它屬於該實例前往“true”，不然將前往“false”。
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")
當我們應用 playground 運轉下面的法式，獲得以下成果。
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
向下轉換
向下類型轉換的子類型可以有兩個操作符（如：as? 和 as!）。as? 當值是nil，前往一個可選值。它是用來檢討勝利向下轉型。
“as!” 前往強迫解包裹，如可選鏈，向下轉換前往 nil 值。它用來觸發運轉時毛病在向下轉型湧現毛病時
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)")
}
}
當我們應用 playground 運轉下面的法式，獲得以下成果。
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
類型轉換：任何與任何對象
為了表現實例屬於任何類型包含函數類型，應用“Any”症結字
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")
}
}
當我們應用 playground 運轉下面的法式，獲得以下成果。
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
為了表現是任何類型的類實例，應用AnyObject“症結字
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")
}
}
當我們應用 playground 運轉下面的法式，獲得以下成果。
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
