Variables in Golang

Let us look at the code first. In this two codes that are to be placed in separate files, we explore following things:

Package Scoped Variables vs Local Variables;
Variable declaration vs just the definition
Assignment Operator '=' vs ':='

package main import "fmt" // following variables declaration, no values assigned yet // .. we will assign the values from another function using = operator var a int var name string var truee bool // following variables declaration, no values assigned yet // .. we will assign the values from another function using := operator // // .. we will later see that change in value using := is only in a local scope rather than on a larger scope var aa int var aname string var atruee bool // this variable is defined in package level; // .. and is accessible across all files in the package var package_variable = 30 func main() { // following variable is visible only inside this function var func_variable = 20 fmt.Println("Package Variable is:", package_variable) fmt.Println("Function Variable is:", func_variable) // the function name can begin with small letter since they are in same package // .. the function name must be upper case if they are in different packages funcInAnotherFile() fmt.Println("** Assign values using = operator. **") // assign values to the variables as following fmt.Println("=========") a = 58 fmt.Println("From main function: Value of a is ", a) assignValuesToVariables() // print the values here again // .. following demonstrates that assigning to the values are local to the calling function fmt.Println("=========") fmt.Println("From main function: Name:", name, ",Bool Value:", truee, ",Int:", a) fmt.Println("=========") fmt.Println("** Assign values using := operator. **") // assign values to the variables as following fmt.Println("=========") aa := 58 fmt.Println("From main function: Value of aa is ", aa) aassignValuesToVariables() // print the values here again // .. following demonstrates that assigning to the values are local to the calling function fmt.Println("=========") fmt.Println("From main function: Name:", aname, ",Bool Value:", atruee, ",Int:", aa) }

The called function is defined at code at 2_anotherfile.go .

package main import "fmt" // the function name can begin with small letter since they are in same package // .. the function name must be upper case if they are in different packages func funcInAnotherFile() { fmt.Println("Printing from another file:", package_variable) } func assignValuesToVariables() { fmt.Println("Before Updating Name:", name, ",Bool Value:", truee, ",Int:", a) name = "Katherine" truee = true a = 34 fmt.Println("From another function: Name:", name, ",Bool Value:", truee, ",Int:", a) } func aassignValuesToVariables() { fmt.Println("Before Updating Name:", aname, ",Bool Value:", atruee, ",Int:", aa) aname := "aKatherine" atruee = true aa = 340 fmt.Println("From another function: Name:", aname, ",Bool Value:", atruee, ",Int:", aa) }

Following is the output of the above code:

prawarpoudel@Prawars-MBP 2.variables % ./project2 Package Variable is: 30 Function Variable is: 20 Printing from another file: 30 ** Assign values using = operator. ** ========= From main function: Value of a is 58 Before Updating Name: ,Bool Value: false ,Int: 58 From another function: Name: Katherine ,Bool Value: true ,Int: 34 ========= From main function: Name: Katherine ,Bool Value: true ,Int: 34 ========= ** Assign values using := operator. ** ========= From main function: Value of aa is 58 Before Updating Name: ,Bool Value: false ,Int: 0 From another function: Name: aKatherine ,Bool Value: true ,Int: 340 ========= From main function: Name: ,Bool Value: true ,Int: 58