Let's dive deep into structs in Go — one of the most fundamental and powerful data structures in the language.

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🧱 What is a Struct?

A struct in Go is a composite data type (i.e., it groups multiple values into a single unit). It's used to create custom data types that model real-world entities — like User, Product, Book, Transaction, etc.

Think of a struct as a class without methods, though we can attach methods to structs in Go.

---

🧪 Declaring a Struct

type User struct {
	Name string
	Age  int
}

• User is a new custom type.
• It has two fields: Name and Age.

This is definition only. To use it, we need to create instances.

---

🧬 Creating Struct Instances

1. Using Struct Literal

user := User{Name: "Skyy", Age: 29}

2. Without Field Names (order matters)

user := User{"Skyy", 29}

✅ Not recommended for readability

3. Declare and then assign

var user User
user.Name = "Skyy"
user.Age = 29

---

🔍 Accessing and Modifying Fields

fmt.Println(user.Name) // "Skyy"

user.Age = 30

---

🪄 Zero Values

If you declare a struct without assigning fields:

var u User
fmt.Println(u) // {"" 0}

• All fields get zero values ("" for string, 0 for int, etc.)

---

🧭 Pointers to Structs

Just like with any type, we can create pointers to structs:

u := &User{Name: "Skyy", Age: 29}
fmt.Println(u.Name) // Go automatically dereferences u

Go provides syntactic sugar: u.Name is the same as (*u).Name.

This is very useful when passing structs to functions or mutating data.

---

🧮 Structs with Methods

We can associate methods with a struct type:

func (u User) Greet() {
	fmt.Println("Hello,", u.Name)
}

This is a value receiver – works on a copy of User.

If we want to mutate fields, use a pointer receiver:

func (u *User) UpdateName(newName string) {
	u.Name = newName
}

---

📦 Embedding Structs (Composition)

Go doesn’t support inheritance but allows embedding.

type Address struct {
	City  string
	State string
}

type Employee struct {
	Name string
	Age  int
	Address // embedded struct
}

Now you can access Employee.City directly:

emp := Employee{Name: "Skyy", Age: 29, Address: Address{"Kolkata", "WB"}}
fmt.Println(emp.City) // "Kolkata"

---

🌐 Struct Tags (Used in JSON, Database)

Struct tags add metadata used by packages like encoding/json, gorm, etc.

type User struct {
	Name string `json:"name"`
	Age  int    `json:"age"`
}

Used with packages like:

json.Marshal(user) // produces {"name":"Skyy","age":29}

---

🧾 Anonymous Structs

Quick way to declare a one-time struct:

emp := struct {
	Name string
	Age  int
}{"Skyy", 29}

---

🗃️ Array/Slice of Structs

users := []User{
	{Name: "Alice", Age: 25},
	{Name: "Bob", Age: 30},
}

---

🧠 Best Practices with Structs

Tip	Description
Use field names when initializing	Improves readability
Use pointer receivers for mutation	Avoid unnecessary copies
Group related fields logically	Easier to maintain and understand
Use struct tags for API/database	Interoperability with other systems
Use embedded structs for reuse	Clean, DRY design without inheritance complexity

---

🧰 Real World Example

type Product struct {
	ID       string  `json:"id"`
	Name     string  `json:"name"`
	Price    float64 `json:"price"`
	InStock  bool    `json:"in_stock"`
}

func (p *Product) ApplyDiscount(discount float64) {
	p.Price = p.Price - (p.Price * discount / 100)
}

---

Let's dive deep into structs in Go — one of the most fundamental and powerful data structures in the language.

---

🧱 What is a Struct?

A struct in Go is a composite data type (i.e., it groups multiple values into a single unit). It's used to create custom data types that model real-world entities — like User, Product, Book, Transaction, etc.

Think of a struct as a class without methods, though we can attach methods to structs in Go.

---

🧪 Declaring a Struct

type User struct {
	Name string
	Age  int
}

• User is a new custom type.
• It has two fields: Name and Age.

This is definition only. To use it, we need to create instances.

---

🧬 Creating Struct Instances

1. Using Struct Literal

user := User{Name: "Skyy", Age: 29}

2. Without Field Names (order matters)

user := User{"Skyy", 29}

✅ Not recommended for readability

3. Declare and then assign

var user User
user.Name = "Skyy"
user.Age = 29

---

🔍 Accessing and Modifying Fields

fmt.Println(user.Name) // "Skyy"

user.Age = 30

---

🪄 Zero Values

If you declare a struct without assigning fields:

var u User
fmt.Println(u) // {"" 0}

• All fields get zero values ("" for string, 0 for int, etc.)

---

🧭 Pointers to Structs

Just like with any type, we can create pointers to structs:

u := &User{Name: "Skyy", Age: 29}
fmt.Println(u.Name) // Go automatically dereferences u

Go provides syntactic sugar: u.Name is the same as (*u).Name.

This is very useful when passing structs to functions or mutating data.

---

🧮 Structs with Methods

We can associate methods with a struct type:

func (u User) Greet() {
	fmt.Println("Hello,", u.Name)
}

This is a value receiver – works on a copy of User.

If we want to mutate fields, use a pointer receiver:

func (u *User) UpdateName(newName string) {
	u.Name = newName
}

---

📦 Embedding Structs (Composition)

Go doesn’t support inheritance but allows embedding.

type Address struct {
	City  string
	State string
}

type Employee struct {
	Name string
	Age  int
	Address // embedded struct
}

Now you can access Employee.City directly:

emp := Employee{Name: "Skyy", Age: 29, Address: Address{"Kolkata", "WB"}}
fmt.Println(emp.City) // "Kolkata"

---

🌐 Struct Tags (Used in JSON, Database)

Struct tags add metadata used by packages like encoding/json, gorm, etc.

type User struct {
	Name string `json:"name"`
	Age  int    `json:"age"`
}

Used with packages like:

json.Marshal(user) // produces {"name":"Skyy","age":29}

---

🧾 Anonymous Structs

Quick way to declare a one-time struct:

emp := struct {
	Name string
	Age  int
}{"Skyy", 29}

---

🗃️ Array/Slice of Structs

users := []User{
	{Name: "Alice", Age: 25},
	{Name: "Bob", Age: 30},
}

---

🧠 Best Practices with Structs

Tip	Description
Use field names when initializing	Improves readability
Use pointer receivers for mutation	Avoid unnecessary copies
Group related fields logically	Easier to maintain and understand
Use struct tags for API/database	Interoperability with other systems
Use embedded structs for reuse	Clean, DRY design without inheritance complexity

---

🧰 Real World Example

type Product struct {
	ID       string  `json:"id"`
	Name     string  `json:"name"`
	Price    float64 `json:"price"`
	InStock  bool    `json:"in_stock"`
}

func (p *Product) ApplyDiscount(discount float64) {
	p.Price = p.Price - (p.Price * discount / 100)
}

---