Go Short Variable Declaration Operator(:=)

The short variable declaration operator (:=) in Golang is used to create variables with appropriate names and initial values. The main purpose of this operator is to declare and initialize local variables within functions and to narrow the scope of variables. The type of the variable is determined by the type of the expression. The var keyword is also used to create variables of specific types. So you can say that there are two ways to create variables in Golang, as shown below:

• Use the var keyword

• Use the short variable declaration operator (:=)

In this article, we will only discuss the short variable declaration operator. To understand the var keyword, you canIn GoReferencevar keyword.

Syntax for using the short variable declaration operator:

variable_name := expression or value

Here, variables must be initialized immediately after declaration without mentioning their type, and the expression or value on the right is used to evaluate the variable type. The use of the var keyword can avoid initialization at the time of declaration.

Example:}}Here, we declare variables using the short declaration operator and do not specify the variable type. The variable type is determined by:=The type of the expression on the right side of the operator determines.

package main
import "fmt"
func main() {
　　　　//Variable declaration and initialization
　　　　a :=　30
　　　　//Accept a string variable
　　　　Language := "Go Language Basic Tutorial"
　　　　fmt.Println("a's value: ", a)
　　　　fmt.Println("Language's value: ", Language)
}

Output:

a's value:　　30
Language's value: Go Language Basic Tutorial

Declare multiple variables using the short declaration operator (:=)

The short declaration operator can also be used to declare multiple variables in a single declarationThe same type or different typesMultiple variables. The types of these variables are determined by:=Evaluate the expression on the right side of the operator.

package main
import "fmt"
func main() {
　　　　//Multiple variables of the same type (int)
　　　　w3codebox1, w3codebox2, w3codebox3　:=　117,　7834,　5685
　　　　//Multiple variables of different types
　　　　w3codebox4, w3codebox5, w3codebox6　:= "GFG",　859.24,　1234
　　　　//Display the value and variable type
　　　　fmt.Printf("w3codebox1　The value is : %d\n3codebox1)}
　　　　fmt.Printf("w3codebox1　The type is : %T\n3codebox1)}
　　　　fmt.Printf("\nw3codebox2　The value is : %d\n3codebox2)}
　　　　fmt.Printf("w3codebox2　The type is : %T\n3codebox2)}
　　　　fmt.Printf("\nw3codebox3　The value is : %d\n3codebox3)}
　　　　fmt.Printf("w3codebox3　The type is : %T\n3codebox3)}
　　　　fmt.Printf("\nw3codebox4　The value is : %s\n3codebox4)}
　　　　fmt.Printf("w3codebox4　The type is : %T\n3codebox4)}
　　　　fmt.Printf("\nw3codebox5　The value is : %f\n3codebox5)}
　　　　fmt.Printf("w3codebox5　The type is : %T\n3codebox5)}
　　　　fmt.Printf("\nw3codebox6　The value is : %d\n3codebox6)}
　　　　fmt.Printf("w3codebox6　The type is : %T\n3codebox6)}
}

Output:

w3codebox1　The value is :　117
w3codebox1　The type is : int
w3codebox2　The value is :　7834
w3codebox2　The type is : int
w3codebox3　The value is :　5685
w3codebox3　The type is : int
w3codebox4　The value is : GFG
w3codebox4　The type is : string
w3codebox5　The value is :　859.240000
w3codebox5　The type is : float64
w3codebox6　The value is :　1234
w3codebox6　The type is : int

:= Declares a local variable or a global variable?

With the short variable declaration operator (:=),You can only declareonly have block scopelocal variables. Usually, local variables are declared within a functional block. If you try to declare a global variable using the short declaration operator (:=), an error message will be thrown.

package main　　
　　　　
import "fmt"
　　　　
//Declare using the var keyword
//And initialize the variable
//It is a package variable, or you can say it is a global scope
var w3codebox1　:=　900　　
　　　　
//Use short variable declarations
//It will throw an error
w3codebox2　:=　200　　
　　　　
func main() {　　
　　　　
//Accessing w inside a function3codebox1
fmt.Println(w3codebox1)}　　
　　　
//　Accessing w inside a function3codebox2
fmt.Println(w3codebox2)}　　
　　　　　　　　
}

Output error:

.\test.go:12:1: syntax error: non-declaration statement outside function body
#.\test.go:12:1: Syntax error: non-declaration statement outside function body

package main
import "fmt"
//Declare a global variable using var
var w3codebox1　:=　900
func main() {
　　　　//Use short variable declarations
　　　　//Inside the main function
　　　　//It has a local scope, which means it cannot
　　　　//Accessing outside the main function
　　　　w3codebox2　:=　200
　　　　//Accessing w inside a function3codebox1
　　　　fmt.Println(w3codebox1)}
　　　　//Accessing w inside a function3codebox2
　　　　fmt.Println(w3codebox2)}
}

Output:

900
200