Example of Strategy Pattern in Golang

What is Strategy Pattern

The strategy is a behavior pattern. It fits where multiple choices for an interface are available and the design would allow switching them dynamically.

Conditions

• A set of choices with similarities in the interface
• Dynamic update of a choice

Example

1. A cache with evictions

• Multiple eviction algorithms
• A cache could switch to a different algorithm dynamically

2. A duck type has a variety of flying behaviors. A duck can fly very fast, slow, and no-fly.

Implementation

Define what a duck is.

// duck_type.go

package main
type duck struct {
	flyBehavior
}

Define fly behavior

// fly_behavior.go

package main
type flyBehavior interface {
	fly()
	nofly()
}

Define the fast duck fly behavior

//fast_duck.go

package main
import "fmt"
type duckF18 struct {
}
func (d *duckF18) fly() {
	fmt.Printf("%+v\n", "flying like a F18")
}
func (d *duckF18) nofly() {
	fmt.Printf("%+v\n", "not implemented")
}

Define no-fly behavior

// nofly_duck.go

package main
import "fmt"
type duckNofly struct {
}
func (d *duckNofly) fly() {
	fmt.Printf("%+v\n", "not implemented")
}
func (d *duckNofly) nofly() {
	fmt.Printf("%+v\n", "no flying")
}

// main.go

package main
func createNewDuck(f flyBehavior) *duck {
	return &duck{
		flyBehavior: f,
	}
}
func (d *duck) setFlyBehavior(f flyBehavior) {
	d.flyBehavior = f
}
func main() {
	// f18 duck
	aDuck := createNewDuck(&duckF18{})
	aDuck.flyBehavior.fly()
    // duck switches to no fly
	aDuck.setFlyBehavior(&duckNofly{})
	aDuck.flyBehavior.fly()
}

References

1. https://golangbyexample.com/strategy-design-pattern-golang/
2. https://www.youtube.com/watch?v=9uDFHTWCKkQ