Go变量声明

go变量类型声明

• 变量短声明
  go语言是强类型语言所以在变量的声明中制定类型，但是在方法中声明的变量可以不需要关键字var以及变量类型，系统
  会自动识别， fmt函数中 %v 输出为相应值的默认格式 ,%T 格式化输出该值的类型。

func main() {
    a := 10
    b := "golang"
    c := 4.17
    d := true
    e := "Hello"
    f := `Do you like my hat?`
    g := 'M'
    fmt.Printf("%v \n", a)
    fmt.Printf("%v \n", b)
    fmt.Printf("%v \n", c)
    fmt.Printf("%v \n", d)
    fmt.Printf("%v \n", e)
    fmt.Printf("%v \n", f)
    fmt.Printf("%v \n", g)
    fmt.Printf("%T \n", a)
    fmt.Printf("%T \n", b)
    fmt.Printf("%T \n", c)
    fmt.Printf("%T \n", d)
    fmt.Printf("%T \n", e)
    fmt.Printf("%T \n", f)
    fmt.Printf("%T \n", g)
}

• 变量默认值

func main() {
    var a int
    var b string
    var c float64
    var d bool
    fmt.Printf("%v \n", a)
    fmt.Printf("%v \n", b)
    fmt.Printf("%v \n", c)
    fmt.Printf("%v \n", d)
}

输出为0 "" 0 false

• 变量带类型先声明后赋值

func main() {
    var message string
    message = "Hello World."
    fmt.Println(message)
}

• 多变量同类型先声明后赋值

func main() {
    var message string
    var a, b, c int
    a = 1
    message = "Hello World!"
    fmt.Println(message, a, b, c)
}

• 多变量同类型声明同时赋值

func main() {
    var message = "Hello World!"
    var a, b, c int = 1, 2, 3
    fmt.Println(message, a, b, c)
}

• 多变量推断类型(同类型)声明同时赋值
  在方法中或者其他代码块中都可以使用，可以定义一个自己不确定的变量类型

func main() {
    var message = "Hello World!"
    var a, b, c = 1, 2, 3
    fmt.Println(message, a, b, c)
}

• 多变量推断类型(不同类型)声明同时赋值

func main() {
    var message = "Hello World!"
    var a, b, c = 1, false, 3
    fmt.Println(message, a, b, c)
}

• 变量各种声明的形式

package main
import "fmt"
var a = "this is stored in the variable a"     // package scope
var b, c string = "stored in b", "stored in c" // package scope
var d string                                   // package scope
func main() {
    d = "stored in d" // declaration above; assignment here; package scope
    var e = 42        // function scope - subsequent variables have func scope:
    f := 43
    g := "stored in g"
    h, i := "stored in h", "stored in i"
    j, k, l, m := 44.7, true, false, 'm' // single quotes
    n := "n"                             // double quotes
    o := `o`                             // back ticks
    fmt.Println("a - ", a)
    fmt.Println("b - ", b)
    fmt.Println("c - ", c)
    fmt.Println("d - ", d)
    fmt.Println("e - ", e)
    fmt.Println("f - ", f)
    fmt.Println("g - ", g)
    fmt.Println("h - ", h)
    fmt.Println("i - ", i)
    fmt.Println("j - ", j)
    fmt.Println("k - ", k)
    fmt.Println("l - ", l)
    fmt.Println("m - ", m)
    fmt.Println("n - ", n)
    fmt.Println("o - ", o)
}