Struct Methods | Structs

Introduction

In Go programming, structs (short for structures) are collections of fields. Methods are functions that operate on instances of a struct type. Combining structs and methods allows for an object-oriented approach to programming in Go. This tutorial will walk you through the fundamentals of defining and using methods on structs.

Defining a Struct

First, let's define a simple struct called Person that has two fields: Name and Age.

type Person struct {
    Name string
    Age  int
}

Defining Methods

Methods are defined on struct types. The syntax for defining a method is similar to that of a function, but it includes a receiver argument. The receiver specifies the type the method is defined on. Here is an example of a method called Greet for the Person struct:

func (p Person) Greet() {
    fmt.Printf("Hello, my name is %s and I am %d years old.\n", p.Name, p.Age)
}

In this example, (p Person) is the receiver, meaning that the Greet method can be called on instances of the Person struct.

Calling Methods

To call a method on a struct, you first need to create an instance of that struct. Then you can call the method using dot notation. Here is an example:

func main() {
    person := Person{Name: "Alice", Age: 30}
    person.Greet()
}

When you run the above code, the output will be:

Hello, my name is Alice and I am 30 years old.

Pointer Receivers

You can also define methods with pointer receivers. Using a pointer receiver allows the method to modify the value that its receiver points to. Here's an example method HaveBirthday that increments the Age field:

func (p *Person) HaveBirthday() {
    p.Age++
}

To call this method:

func main() {
    person := Person{Name: "Alice", Age: 30}
    person.HaveBirthday()
    person.Greet() // Now should say 31 years old
}

When you run the above code, the output will be:

Hello, my name is Alice and I am 31 years old.

Method Sets

In Go, the set of methods that can be called on a value is determined by its type. For a type T, the method set includes all methods with receiver type T. For a type *T, the method set includes all methods with receiver type T or *T. This distinction is important when dealing with interfaces.

Conclusion

In this tutorial, we've covered the basics of defining and using methods on structs in Go. We've seen how to define methods with both value and pointer receivers and how to call these methods on struct instances. Understanding these concepts is crucial for structuring Go programs in an object-oriented manner.

Struct Methods in Go Programming