go / beginner
Snippet
Interfaces: Defining Behavior Contracts
Interfaces define a contract of methods that a type must implement. They enable polymorphism in Go, allowing different types to satisfy the same interface. When a type implements all methods in an interface, it implicitly satisfies that interface. Go is duck-typed, meaning you don't need to explicitly declare that a type implements an interface. This makes code flexible and testable. Empty interface (interface{}) can hold any value.
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package mainimport "fmt"type Speaker interface {Speak() string}type Dog struct{}func (d Dog) Speak() string {return "Woof!"}type Cat struct{}func (c Cat) Speak() string {return "Meow!"}func main() {var s Speakers = Dog{}fmt.Println("Dog says:", s.Speak())s = Cat{}fmt.Println("Cat says:", s.Speak())// Using a slice of interfacesspeakers := []Speaker{Dog{}, Cat{}}for _, speaker := range speakers {fmt.Println("Animal says:", speaker.Speak())}}
Breakdown
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type Speaker interface { Speak() string }
Defines an interface requiring a Speak() method returning a string
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func (d Dog) Speak() string
Value receiver method - Dog type implements Speaker
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var s Speaker
Declares a variable of interface type, initially nil
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speakers := []Speaker{Dog{}, Cat{}}
Slice of interface type holding different concrete types