Structs in Go

Structs are one of the most important data structures in Go. They allow you to group related data into a single unit. Structs are widely used to represent real-world entities such as users, orders, products, employees, and configurations.

In real applications, structs form the foundation of APIs, databases, services, and business logic.

Why Structs Are Needed

So far, you have worked with individual variables. But real programs deal with related data.

• User details (name, email, age)
• Bank account (account number, balance, status)
• Product information (id, price, quantity)

Structs allow you to model such data cleanly and logically.

Defining a Struct

A struct is defined using the type keyword followed by the struct keyword.

type User struct {
    ID    int
    Name  string
    Age   int
    Email string
}

This defines a new data type called User that groups multiple fields together.

Creating Struct Values

Once defined, you can create struct values using different methods.

Method 1: Field-by-field Initialization

user := User{
    ID:    101,
    Name:  "Arjun",
    Age:   28,
    Email: "arjun@example.com",
}

This approach is clear and preferred in production code.

Method 2: Positional Initialization

user := User{101, "Arjun", 28, "arjun@example.com"}

This works but is error-prone and not recommended for large structs.

Accessing Struct Fields

You access struct fields using the dot (.) operator.

fmt.Println(user.Name)
fmt.Println(user.Age)

Each field behaves like a normal variable.

Modifying Struct Fields

Struct fields can be updated directly.

user.Age = 29
user.Email = "arjun.new@example.com"

This updates only the specific fields without affecting the rest.

Structs with Pointers

In real applications, structs are often passed as pointers to avoid copying large amounts of data.

func updateEmail(u *User, newEmail string) {
    u.Email = newEmail
}

func main() {
    user := User{ID: 102, Name: "Meera", Age: 31, Email: "meera@example.com"}
    updateEmail(&user, "meera.work@example.com")
    fmt.Println(user.Email)
}

Go automatically dereferences struct pointers, making pointer-based code clean and readable.

Real-World Example: Bank Account

Structs are perfect for modeling financial data.

type Account struct {
    AccountNumber string
    Balance       float64
    Active        bool
}

func deposit(a *Account, amount float64) {
    a.Balance += amount
}

func main() {
    acc := Account{
        AccountNumber: "ACC-9001",
        Balance:       2500.50,
        Active:        true,
    }

    deposit(&acc, 749.50)
    fmt.Println("Balance:", acc.Balance)
}

This pattern is widely used in banking and payment systems.

Nested Structs

Structs can contain other structs as fields.

type Address struct {
    City  string
    State string
}

type Customer struct {
    Name    string
    Address Address
}

This helps model complex real-world data hierarchies.

Zero Values in Structs

When a struct is declared without initialization, each field gets its zero value.

• int → 0
• string → ""
• bool → false

Best Practices

• Use structs to model real-world entities
• Prefer named field initialization
• Pass structs by pointer when large
• Keep structs focused and meaningful

What’s Next?

In the next lesson, you will learn about Methods in Go, which allow functions to be attached directly to structs.