Structs, Methods, Interfaces, Composition, and Go Style OOP Thinking
Understand how Go models data and behavior without traditional class-heavy object orientation.
Inside this chapter
- Structs as Core Building Blocks
- Methods
- Interfaces
- Composition Over Inheritance
- Real Example
Series navigation
Study the chapters in order for the clearest path from Golang basics to advanced concurrency, service design, and production engineering. Use the navigation at the bottom to move smoothly through the full tutorial series.
Structs as Core Building Blocks
type User struct {
ID int
Name string
Email string
}Structs group related fields together and act as the main custom data type in Go. They are central to domain modeling, transport objects, configs, and service dependencies.
Methods
func (u User) DisplayName() string {
return u.Name + " <" + u.Email + ">"
}Methods attach behavior to structs, giving Go a clean way to model domain logic without requiring inheritance-heavy design.
Interfaces
type Notifier interface {
Send(message string) error
}Interfaces define behavior contracts. In Go, types satisfy interfaces implicitly, which often makes code more flexible and less tightly coupled than explicit implementation declarations.
Composition Over Inheritance
Go strongly favors composition and small interfaces over deep inheritance hierarchies. This often leads to simpler, more modular designs that are easier to test and evolve.
Real Example
A payment service might use a struct for payment data, interfaces for storage or notification dependencies, and composition to assemble behavior. This is a common Go approach to backend architecture.