Swift中optionals使用总结

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let optional: String? = "unicorn"
var optional2: Int?
let optionals: [String?] = ["unicorn", nil, "dragon"]
var optionals2: [Int]?

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if let value = optional {

// 多变量
if let value = optional, let value2 = optional2 {

// 布尔值判断从句（boolean clause）
if let value = optional, value.hasSuffix("saurus") {

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guard let value = optional else { 
  return
}

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while let value = optional {

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let value = optional ?? "nil"

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let value = optional!

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switch optional {
case .some(let value):
  print(value)
case .none:
  print("nil")
}

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let value = optional.map(String.init(describing:))

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let value = optional.flatMap(URL.init(string:))

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let values = optionals.compactMap { $0 }

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let value = optional as! String

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let value = optional?.uppercased()

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for element in optionals {
  if let value = element {

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for case let optional? in optionals {

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optionals?.forEach { value in

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try? aThrowingCall()
try! aThrowingCall()