I ran into an a blog All Design Patterns in Go (Golang) but feel that it does not have to be this OOP and this complicated in Go. So I will try to re-implement these patterns in a more Go-ish way.

Behavioural Design Patterns

Observer pattern

Go has very good support for functional programming, making a lot of object-ish wrappers unnecessary.
Instead of having the observer interface receiving a function, I can directly keep track of the functions to be invoked at events:

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type item struct {
	observerFuncs map[string]func(string)
	name          string
	inStock       bool
}

The functions to notify can be directly be registered to and invoked by the subject:

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func (i *item) register(id string) {
	if i.notifyFuncs == nil {
		i.notifyFuncs = map[string]func(string){}
	}
	i.notifyFuncs[id] = customerNotificationFunc(id)
}

func (i *item) notifyAll() {
	for _, notifyFunc := range i.notifyFuncs {
		notifyFunc(i.name)
	}
}

Strategy pattern

While I’m here let me implement the caching strategies in full.

  • Extended the item data type to keep track of the accessCount, lastAccessed time and lastUpdated time
  • Implemented the algos - although now not wrapped in an interface but passed in as a function.