Go language: constructor functions

Unlike other languages Java, Go do not have any constructor functions to initialize an object. But you can write custom functions to initialize the object.

Example

func getEmployee(name string, id int, hobbies []string) Employee{

         emp := Employee{}

         emp.name = name

         emp.id = id

         emp.hobbies = hobbies

         return emp

}

HelloWorld.go

package main

import "fmt"

func main() {
 emp1 := getEmployee("Krishna", 1, []string{"Cricket", "Football"})

 fmt.Println("name : ", emp1.name)
 fmt.Println("id : ", emp1.id)
 fmt.Println("hobbies : ", emp1.hobbies)
}

type Employee struct{
 name string
 id int

 hobbies []string
} 

func getEmployee(name string, id int, hobbies []string) Employee{
 emp := Employee{}

 emp.name = name
 emp.id = id
 emp.hobbies = hobbies

 return emp
}

Output

name :  Krishna

id :  1

hobbies :  [Cricket Football]

You can enhance the constructor function by adding some validation checks.

func getEmployee(name string, id int, hobbies []string) (*Employee, error) {

         if name == "" {

                  return nil, fmt.Errorf("Name can't be nil")

         }

         if id <= 0 {

                  return nil, fmt.Errorf("id can't be zero")

         }

         emp := Employee{}

         emp.name = name

         emp.id = id

         emp.hobbies = hobbies

         return &emp, nil

}

HelloWorld.go

package main

import "fmt"

func main() {
 emp1, err1 := getEmployee("Krishna", 1, []string{"Cricket", "Football"})

 if err1 != nil {
  fmt.Println("Error Occurred while creating employee")
  fmt.Println(err1)
 } else {
  emp1.printEmployeeInfo()
 }

 emp2, err2 := getEmployee("Krishna", -10, []string{"Cricket", "Football"})

 if err2 != nil {
  fmt.Println("Error Occurred while creating employee")
  fmt.Println(err2)
 } else {
  emp2.printEmployeeInfo()
 }

}

type Employee struct {
 name string
 id   int

 hobbies []string
}

func (emp *Employee) printEmployeeInfo() {
 fmt.Println("name : ", emp.name, ", id : ", emp.id, ", hobbies : ", emp.hobbies)
}

func getEmployee(name string, id int, hobbies []string) (*Employee, error) {
 if name == "" {
  return nil, fmt.Errorf("Name can't be nil")
 }

 if id <= 0 {
  return nil, fmt.Errorf("id can't be zero")
 }

 emp := Employee{}

 emp.name = name
 emp.id = id
 emp.hobbies = hobbies

 return &emp, nil
}

Output

name :  Krishna , id :  1 , hobbies :  [Cricket Football]

Error Occurred while creating employee

id can't be zero

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