Swift 字符串

import Cocoa

// 使用字符串字面量
var stringA = "Hello,World!"
print( stringA )

// String 实例化
var stringB = String("Hello,World!")
print( stringB )

Hello,World!
Hello,World!

import Cocoa

// 使用字符串字面量创建空字符串
var stringA = ""

if stringA.isEmpty {
   print( "stringA 是空的" )
} else {
   print( "stringA 不是空的" )
}

// 实例化 String 类来创建空字符串
let stringB = String()

if stringB.isEmpty {
   print( "stringB 是空的" )
} else {
   print( "stringB 不是空的" )
}

stringA 是空的
stringB 是空的

import Cocoa

// stringA 可被修改
var stringA = "菜鸟教程："
stringA += "http://www.runoob.com"
print( stringA )

// stringB 不能修改
let stringB = String("学习：")
stringB += "http://www.学习.com"
print( stringB )

error: left side of mutating operator isn‘t mutable: ‘stringB‘ is a ‘let‘ constant
stringB += "http://www.runoob.com"

import Cocoa

var varA   = 20
let constA = 100
var varC:Float = 20.0

var stringA = "\(varA) 乘于 \(constA) 等于 \(varC * 100)"
print( stringA )

20 乘于 100 等于 2000.0

import Cocoa

let constA = "学习："
let constB = "http://www.学习.com"

var stringA = constA + constB

print( stringA )

import Cocoa

var unicodeString   = "学习"

print("UTF-8 编码: ")
for code in unicodeString.utf8 {
   print("\(code) ")
}

print("\n")

print("UTF-16 编码: ")
for code in unicodeString.utf16 {
   print("\(code) ")
}