Strings

A string in Go is an immutable（不可变的） sequence of bytes, which don't necessarily have to represent characters.
double quotes("") 和 backticks(`)的区别：双引号里可能有特殊字符（Special characters），例如\t, \n等，不能换行。反引号，raw string literal，没有特殊字符，没有\代表转义这一说，可以换行。
Raw string literals use backticks (`) as their delimiter instead of double quotes and all characters in it are interpreted literally, meaning that there is no need to escape characters or newlines.

const daltons = `Joe
William
Jack
Averell`

`abc`
// same as "abc"

"\"" // regular string literal with 1 character: a double quote
// same as `"` a raw string literal with 1 character: a double quote

`\n
` // raw string literal with 3 character: a backslash, an 'n', and a newline
// same as "\\n\n"  a regular string literal with 3 characters: a backslash, an 'n', and a newline

"\t\n" // regular string literal with 2 characters: a tab and a newline
`\t\n`// raw string literal with 4 characters: two backslashes, a 't', and an 'n'

Special characters

Strings Package

常用函数

func ToLower(s string) string
func ToUpper(s string) string

//Trim leading and trailing whitespace
func TrimSpace(s string) string

//Find the index of the first instance of a substring within a string
func Index(s, substr string) int

func Replace(s, old, new string, n int) string
func ReplaceAll(s, old, new string) string
func Split(s, sep string) []string

//测试字符串 s 是否以 suffix 结尾。
func HasSuffix(s, suffix string) bool

//Count the number of occurrences of a substring within a string
func Count(s, substr string) int

//Repeat returns a new string consisting of count copies of the string s.
//It panics if count is negative or if the result of (len(s) * count) overflows.
func Repeat(s string, count int) string
// strings.Repeat returns a string with a substring given as argument repeated many times
strings.Repeat("Go", 3)
// => "GoGoGo"

Exercise

package techpalace
import "strings"


// WelcomeMessage returns a welcome message for the customer.
func WelcomeMessage(customer string) string {
    return "Welcome to the Tech Palace, " + strings.ToUpper(customer)
}

// AddBorder adds a border to a welcome message.
func AddBorder(welcomeMsg string, numStarsPerLine int) string {
    return strings.Repeat("*", numStarsPerLine) + "\n" + welcomeMsg + "\n" + strings.Repeat("*", numStarsPerLine)
}

// CleanupMessage cleans up an old marketing message.
func CleanupMessage(oldMsg string) string {
    res := strings.ReplaceAll(oldMsg, "*", "")
    res = strings.TrimSpace(res)
    return res
}