Swiftmap和filter函数原型基础示例,
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Swiftmap和filter函数原型基础示例,
目录
- map函数原型
- filter函数原型
map函数原型
/// Returns an array containing the results of mapping the given closure /// over the sequence's elements. /// /// In this example, `map` is used first to convert the names in the array /// to lowercase strings and then to count their characters. /// /// let cast = ["Vivien", "Marlon", "Kim", "Karl"] /// let lowercaseNames = cast.map { $0.lowercased() } /// // 'lowercaseNames' == ["vivien", "marlon", "kim", "karl"] /// let letterCounts = cast.map { $0.count } /// // 'letterCounts' == [6, 6, 3, 4] /// /// - Parameter transform: A mapping closure. `transform` accepts an /// element of this sequence as its parameter and returns a transformed /// value of the same or of a different type. /// - Returns: An array containing the transformed elements of this /// sequence. @inlinable public func map<T>(_ transform: (Element) throws -> T) rethrows -> [T]
let cast = ["Vivien", "Marlon", "Kim", "Karl"] let lowercaseNames = cast.map { $0.lowercased() } print(lowercaseNames) // ["vivien", "marlon", "kim", "karl"] let arrayString = ["Ann", "Bob", "Tom", "Lily", "HanMeiMei", "Jerry"] // 计算每个元素的个数,生成个数数组 let arrayCount = arrayString.map { (str) -> Int in return str.count } print("arrayCount: \(arrayCount)") // arrayCount: [3, 3, 3, 4, 9, 5]
filter函数原型
// @inlinable public func filter(_ isIncluded: (Element) throws -> Bool) rethrows -> [Element] let array = [-5, 4, -3, 1, 2] var resultArray = array.filter { (item) -> Bool in return item > 0 } print(resultArray) // [4, 1, 2] // 语法糖写法 resultArray = array.filter { $0 > 0 } print(resultArray) // [4, 1, 2]
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