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变量 Varaible

基本变量类型​

bool

string

int  int8  int16  int32  int64
uint uint8 uint16 uint32 uint64 uintptr

byte // alias for uint8

rune // alias for int32
     // represents a Unicode code point

float32 float64

complex64 complex128

声明​

变量声明方式​

正常声明​

var smsSendingLimit int
smsSendingLimit = 60
var costPerSMS float64 = 0.2
var hasPermission bool
var username string

快速声明​

smsSendingLimit := 60
penniesPerText := 2.0
averageOpenRate, displayMessage := .23, "is the average open rate of your messages"

常量 Constant​

常量不能够做任何修改和重新赋值，常量计算是在编译过程中完成。

func calculateTime() {
    const secondsInMinute = 60
    const minutesInHour = 60
    const secondsInHour = minutesInHour * secondsInMinute

    fmt.Println("number of seconds in an hour:", secondsInHour)
}

格式化字符显示​

格式化字符显示不太好用，不太优雅。

  • fmt.Printf - Prints a formatted string to standard out.
  • fmt.Sprintf() - Returns the formatted string
func createUser(firstName, lastName string, age int) {
    fmt.Printf("My name is %s %s, I'm %d years old\n", firstName, lastName, age)
    var returnOfSprintf string = fmt.Sprintf("My name is %s %s, I'm %d years old\n", firstName, lastName, age)
    fmt.Println(returnOfSprintf)
}

%v - Interpolate the default representation

fmt.Printf("I am %v years old\n", 10)
// I am 10 years old
fmt.Printf("I am %v years old\n", "way too many")
// I am way to many years old

%s - Interpolate a string

fmt.Printf("I am %s years old\n", "way too many")
// I am way to many years old

%d - Interpolate an integer in decimal integer form

fmt.Printf("I am %d years old\n", 10)
// I am 10 years old

%f - Interpolate a decimal float

fmt.Printf("I am %f years old\n", 10.523)
// I am 10.523000 years old
fmt.Printf("I am %.2f years old\n", 10.523)
// I am 10.52 years old