<<Swift巩固笔记>> 第3篇 字符串和字符

好玩的地方

1. 可以用 + 拼接字符串

2. 多选字符串的使用

基本使用

// 基本使用
let someString = "Hello, world!"

多行字符串

// 多行字符串
let desc = """
    Hi, I'm Ray.
    I like watching movies!
    I like listening music!
"""

初始化空字符串

// 初始化空字符串
var emptyString = ""
var emptyString2 = String()

判断字符串是否为空 isEmpty()

// 判断字符串是否为空
if emptyString.isEmpty {
    print("it's empty")
} else {
    print("it's not empty")
}

字符串和字符和字符数组

// 遍历字符串中的每一个字符
for c in someString {
    print(c)
}

// 字符类型
let mark:Character = "!"
print(mark)

// 字符数组可以转变为字符串
let characters:[Character] = ["C", "a", "t"]
let catString = String(characters)
print(catString)

字符串拼接

// + 连接符, append()连接函数
var str = someString + catString
str.append(mark)
print(str)

字符串索引

// 字符串索引
let greeting = "Hi, everyone"
print(greeting[greeting.startIndex])

print(greeting[greeting.index(before: greeting.endIndex)])

print(greeting[greeting.index(after: greeting.startIndex)])

let index = greeting.index(greeting.startIndex, offsetBy: 4)
print(greeting[index])

for index in greeting.indices {
    print(greeting[index])
}

插入和删除

// 插入和删除
var welcome = "Hello"
welcome.insert("!", at: welcome.endIndex)
print(welcome)

welcome.insert(contentsOf: " there", at: welcome.index(before: welcome.endIndex))
print(welcome)

welcome.remove(at: welcome.index(before: welcome.endIndex))
print(welcome)

let range = welcome.index(welcome.endIndex, offsetBy: -6) ..< welcome.endIndex
welcome.removeSubrange(range)
print(welcome)

字符串比较

// 比较字符
let quotation = "Ray"
let someQuotation = "Ray"
if quotation == someQuotation {
    print("these two strings are considered equal")
}