Struct in Golang

Golang provides built-in data types like integer, string, float, etc which is very useful for writing simple programs but if you want to write a complex program, you need to create your data types. Struct in Golang helps you to define your data types. If you depend on Golang built-in data types, your code will be very complex and readability is low. Struct gives you the flexibility to create your data types.

• Define a new Struct in Golang
• Create or Initialize an Instance of a struct data type
• Create or Initialize an Instance of a struct data type using the new keyword
• Access Fields of a struct
• Embedded Struct or Types
• References

Define a new Struct in Golang

A struct is a type that contains named fields.

Defining a struct has 4 parts

• type keyword: Define a new type in Golang. You can define a struct or an interface etc, using the type keyword
• Name of Struct: You need to give a unique name to the struct. Here we have given the name as Employee
• struct keyword: It is used to create a new type of struct
• fields: You can add any number of fields to the struct. These are the properties of your new data type.

Let’s say you want to create an Employee management system then you will create an Employee Data type and give meaningful information or properties to the Employee data type.

type Employee struct {

  firstName  string
  middleName string
  lastName   string
  email      string
  age        int
  gender     string
  active     bool
  address    string
  
}

In the above code, we have defined a new data type named Employee. You can create different instances of Employee and use them in your code

Create or Initialize an Instance of a struct data type

There are different ways to initialize a struct data type. The most common way is to give the fields an initial value while initializing the struct.

employeeOne := Employee{

		firstName: "Raj",
		lastName:  "Ranjan",
		email:     "selftuts@gmail.com",
		address:    "Bengaluru India",
	
}

we have created the employeeOne instance from the Employee struct. You can see that when initializing the struct it is not mandatory to provide value to every field. If the value is not provided then a default value is automatically assigned.

Create or Initialize an Instance of a struct data type using the new keyword

You can use the new Keyword of Golang to create a new instance of the struct

employeeOne := new(Employee)

• The fields are assigned default values
  • 0 for integer and float data type
  • empty for string data type
• This allocates memory for all the fields, sets each to its default value, and returns a pointer to the struct (*Employee).

Access Fields of a struct

You can use the dot notation to access the fields of a struct instance

package main

import "fmt"

type Employee struct {
	firstName  string
	middleName string
	lastName   string
	email      string
	age        int
	gender     string
	active     bool
	address    string
}

func main() {
	employeeOne := Employee{
		firstName: "Raj",
		lastName:  "Ranjan",
		email:     "selftuts@gmail.com",
		address:   "Bengaluru India",
	}
  
  // using the dot notation to access the field of a struct instance
	fmt.Println(employeeOne.firstName)
	fmt.Println(employeeOne.lastName)
	fmt.Println(employeeOne.email)
}

➜  go run main.go
Raj
Ranjan
selftuts@gmail.com

Embedded Struct or Types

If your data is complex or nested, you will embed one struct inside another. This is called Embedded Struct or Embedded Types. The address is identified using multiple properties like city, flat number, state, and country. If you want to create a better data model then you will first create an Address struct and then use the Address struct inside the Employee struct

// first we define the Address struct
type Address struct {
	flatNumber string
	city       string
	state      string
	country    string
}

type Employee struct {
	firstName  string
	middleName string
	lastName   string
	email      string
	age        int
	gender     string
	active     bool
	Address    string    // use Address struct as Embedded Type in Employee struct
}

You can see in the above Employee struct that the Address struct is an Embedded type.

References

• YouTube Channel
• Kafka Consumer in Python