Scope of Variables in Go

Prerequisite: Variables in Go Programming Language

The scope of a variable defines the part of the program where that variable is accessible. In Go, all identifiers are lexically scoped, meaning the scope can be determined at compile time. A variable is only accessible within the block of code where it is defined.

Example

package main  
import "fmt"

// Global variable declaration 
var myVariable int = 100 

func main() {
    // Local variable inside the main function 
    var localVar int = 200 
    fmt.Printf("Inside main - Global variable: %d\n", myVariable) 
    fmt.Printf("Inside main - Local variable: %d\n", localVar) 
    display() 
}

func display() {
    fmt.Printf("Inside display - Global variable: %d\n", myVariable) 
}

Syntax

var variableName type = value 

Local Variables

Local variables are declared within a function or a block and are not accessible outside of it. They can also be declared within loops and conditionals but are limited to the block scope.

Example:

package main
import "fmt"

func main() {
    var localVar int = 200 // Local variable
    fmt.Printf("%d\n", localVar) // Accessible here
}

200

Global Variables

Global variables are defined outside any function or block, making them accessible throughout the program.

Example:

package main
import "fmt"

// Global variable declaration 
var myVariable int = 100 // Global variable

func main() {
    fmt.Printf("%d\n", myVariable) // Accessible here
}

100

Local Variable Preference

When a local variable shares the same name as a global variable, the local variable takes precedence within its scope.

Example

package main
import "fmt"

// Global variable declaration 
var myVariable int = 100 // Global variable

func main() {
    var myVariable int = 200 // Local variable
    fmt.Printf("Local variable takes precedence: %d\n", myVariable) // Accesses local variable
}

Local variable takes precedence: 200