String字符串常见用法 生成字符串
创建字符串 let greeting = "Hello, world!" let name = String("John") 连接字符串:使用加号(+)或者字符串插值(使用())来将多个字符串连接起来。 var firstName = "John" let lastName = "Doe" let fullName = firstName + " " + lastName // "John Doe" let fullName1 = firstName.append(lastName) // "My name is John Doe." let message = "My name is \(fullName)." // "My name is John Doe."子字符串查询,替换,插入,删除
查找子字符串 let sentence = "Swift is a powerful and intuitive programming language." if sentence.contains("Swift") { // do something } let range = sentence.range(of: "powerful") // Optional(Range(10..<18)) var str3 = "123456" print(str.hasPrefix("123")) print(str.hasSuffix("456")) 替换字符串 var sentence = "Swift is a powerful and intuitive programming language." sentence = sentence.replacingOccurrences(of: "powerful", with: "amazing") 字符串删除 // 666hello_2_3_8884 str4.remove(at: str4.firstIndex(of: "1")!) // hello_2_3_8884 str4.removeAll { $0 == "6" } var range = str4.index(str4.endIndex, offsetBy: -4)..<str4.index(before: str4.endIndex) // hello_2_3_4 str4.removeSubrange(range) 字符串插入 var str = "Hello, world!" let firstChar = str[str.startIndex] // "H" let lastChar = str[str.index(before: str.endIndex)] // "!" str.insert("!", at: str.endIndex) // "Hello, world!!"字符串转数组
字符串分割 let names = "John, Jane, Jim" let arr = names.components(separatedBy: ", ") // ["John", "Jane", "Jim"]字符串转其他
let str = "123" let num = Int(str) // Optional(123) let uppercased = str.uppercased() // "123"
Array数组高阶操作 map:对给定数组每个元素,执行闭包中的映射,将映射结果放置在数组中返回。 flatMap:对给定数组的每个元素,执行闭包中的映射,对映射结果进行合并操作,然后将合并操作后的结果放置在数组中返回。 compactMap:对给定数组的每个元素,执行闭包中的映射,将非空的映射结果放置在数组中返回。 compactMap:对给定数组的每个元素,执行闭包中的映射,将非空的映射结果-键值对放置在字典中返回。 filter:对给定数组的每个元素,执行闭包中的操作,将符合条件的元素放在数组中返回。 reduce:对给定数组的每个元素,执行闭包中的操作对元素进行合并,并将合并结果返回。
var arr = [1, 2, 3, 4] // [2, 4, 6, 8] var arr2 = arr.map { $0 * 2 } print(arr2) // [2, 4] var arr3 = arr.filter { $0 % 2 == 0 } print(arr3) // 10 var arr4 = arr.reduce(0) { $0 + $1 } print(arr4) // 10 var arr5 = arr.reduce(0, +) print(arr5)
Set集合操作 集合创建
let setA = Set(["a","b","c"]) let setB: Set = ["a","b","c"]增删改查
setA.contains("a") setA.insert("c") setA.remove("a")集合运算
let set1 = Set([1,2,3]) let set2 = Set([1,2]) //运算判断 if set1 == set2 { } // 子集,超集判断 set2.isSubset(of: set1) set1.isSuperset(of: set2) // 并集,交集 set1.union(set2) set1.intersection(set2)
标签:Set,String,映射,let,数组,字符串,John,Swift From: https://www.cnblogs.com/zhou--fei/p/17432566.html