[英]~= operator in Swift
我最近從Apple下載了Advanced NSOperations示例應用程序,並找到了此代碼...
// Operators to use in the switch statement.
private func ~=(lhs: (String, Int, String?), rhs: (String, Int, String?)) -> Bool {
return lhs.0 ~= rhs.0 && lhs.1 ~= rhs.1 && lhs.2 == rhs.2
}
private func ~=(lhs: (String, OperationErrorCode, String), rhs: (String, Int, String?)) -> Bool {
return lhs.0 ~= rhs.0 && lhs.1.rawValue ~= rhs.1 && lhs.2 == rhs.2
}
它似乎對Strings
和Ints
使用~=
運算符,但我從未見過。
它是什么?
它是用於case
語句中的模式匹配的運算符。
您可以在這里了解如何使用和利用它來提供自己的實現:
這是定義和使用自定義變量的簡單示例:
struct Person {
let name : String
}
// Function that should return true if value matches against pattern
func ~=(pattern: String, value: Person) -> Bool {
return value.name == pattern
}
let p = Person(name: "Alessandro")
switch p {
// This will call our custom ~= implementation, all done through type inference
case "Alessandro":
print("Hey it's me!")
default:
print("Not me")
}
// Output: "Hey it's me!"
if case "Alessandro" = p {
print("It's still me!")
}
// Output: "It's still me!"
只需使用快捷方式“范圍”:您可以構造一個范圍,“〜=”表示“包含”。 (其他可以添加更多理論細節,但意義是這樣)。 讀為“包含”
let n: Int = 100
// verify if n is in a range, say: 10 to 100 (included)
if n>=10 && n<=100 {
print("inside!")
}
// using "patterns"
if 10...100 ~= n {
print("inside! (using patterns)")
}
嘗試使用某些n值。
例如在HTTP響應中被廣泛使用:
if let response = response as? HTTPURLResponse , 200...299 ~= response.statusCode {
let contentLength : Int64 = response.expectedContentLength
completionHandler(contentLength)
} else {
completionHandler(nil)
您可以查看Define Swift
func ~=<I : IntervalType>(pattern: I, value: I.Bound) -> Bool
func ~=<T>(lhs: _OptionalNilComparisonType, rhs: T?) -> Bool
func ~=<T : Equatable>(a: T, b: T) -> Bool
func ~=<I : ForwardIndexType where I : Comparable>(pattern: Range<I>, value: I) -> Bool
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