Go ---- variable usage in go language

One 、Go Introduction to variables in language

Variables are abstract concepts in computer language that can store calculation results or represent values . Different variables may hold different data types .

Two 、Go How to use variables in language

2.1 Declare variables

Go Variables in a language need to be declared before they can be used , Duplicate declarations are not supported within the same scope . also Go Language variables must be declared with .

Syntax for declaring variables

var identifier type

among ：

• var： Declare variable keywords

• identifier： Variable name

• type： Variable type

for example

package main

import "fmt"

func main() {
    
	var name string
	var age int
	var ok bool
}

2.2 Batch statement

Use one var keyword , Write some variables in parentheses () in

package main
func main() {
    
	var (
		name string
		age  int
		ok   bool
	)
}

2.3 Initialization of a variable

Go When languages declare variables , It will automatically initialize the memory area corresponding to the variable . Each variable is initialized to the default value of its type , for example ： The default values for integer and floating point variables are 0. The default value of string variable is empty string “”. Boolean variables default to false. section 、 function 、 The default value of pointer variable is nil.

Variable initialization syntax

var  Variable name   type  =  expression 

for example

package main
func main() {
    
	var name string = " Lao Guo "
	var site string = "www.duoke360.com"
	var age int = 30
}

2.4 Type derivation

When we declare variables , Type derivation can be carried out according to the initialization value , Thus omitting the type .

package main
func main() {
    
	var name = " Lao Guo "
	var site = "www.duoke360.com"
	var age = 30
}

2.5 Initialize multiple variables

You can initialize multiple variables at once , Separated by commas .

package main
func main() {
    
	var name, site, age = " Lao Guo ", "www.duoke360.com", 30
}

2.6 Short variable declaration

Inside the function , have access to := Operator to declare and initialize variables .

package main

func main() {
    
	name := " Lao Guo "
	site := "www.duoke360.com"
	age := 20
}

Be careful ： This method is only suitable for inside functions , Function cannot be used outside .

2.7 Anonymous variables

If we receive multiple variables , Some variables are not used , You can use underscores _ Represents the variable name , This variable is called anonymous variable . for example ：

package main

import "fmt"

func getNameAndAge() (string, int) {
    
	return " Lao Guo ", 30
}

func main() {
    
	name, _ := getNameAndAge()
	fmt.Printf("name: %v\n", name)
}```