Go Methods
Adding behavior to your Go types
🔧 What are Go Methods?
Go methods are functions with special receiver arguments that allow you to define behavior for custom types. They enable object-oriented programming patterns in Go's simple and elegant way.
// Define a struct
type Person struct {
Name string
Age int
}
// Define a method for Person
func (p Person) Greet() string {
return "Hello, I'm " + p.Name
}
Output:
Hello, I'm John
Key Method Concepts
Receiver
The type that receives the method
func (p Person) Method() {}Value Receiver
Works with a copy of the value
func (p Person) GetName() stringPointer Receiver
Works with the original value
func (p *Person) SetName(name string)Method Set
All methods available to a type
person.Greet()
person.SetAge(25)🔹 Value vs Pointer Receivers
Understanding when to use value or pointer receivers:
type Counter struct {
count int
}
// Value receiver - doesn't modify original
func (c Counter) GetCount() int {
return c.count
}
// Pointer receiver - modifies original
func (c *Counter) Increment() {
c.count++
}
// Usage
func main() {
counter := Counter{count: 0}
fmt.Println(counter.GetCount()) // 0
counter.Increment()
fmt.Println(counter.GetCount()) // 1
}Output:
0
1
🔹 Methods on Built-in Types
You can define methods on custom types based on built-in types:
// Custom type based on string
type MyString string
// Method for custom type
func (s MyString) Length() int {
return len(string(s))
}
func (s MyString) Upper() MyString {
return MyString(strings.ToUpper(string(s)))
}
// Usage
func main() {
text := MyString("hello world")
fmt.Println(text.Length()) // 11
fmt.Println(text.Upper()) // HELLO WORLD
}Output:
11
HELLO WORLD
🔹 Method Chaining
Return the receiver to enable method chaining:
type Builder struct {
text string
}
func (b *Builder) Add(s string) *Builder {
b.text += s
return b
}
func (b *Builder) AddSpace() *Builder {
b.text += " "
return b
}
func (b *Builder) String() string {
return b.text
}
// Usage
func main() {
result := &Builder{}
final := result.Add("Hello").AddSpace().Add("World").String()
fmt.Println(final) // Hello World
}Output:
Hello World