added comments

go/04-design-pattern/main.go

@@ -6,25 +6,30 @@ import (
 	"gitty.informatik.hs-mannheim.de/steger/pr3-code/go/04-design-pattern/patterns"
 )
 
+// Counter is a concrete implementation of the Subject interface, which maintains a count and notifies observers whenever the count changes
 type Counter struct {
-	patterns.Subject
-	Count int
+	patterns.Subject // Embedding the Subject interface allows Counter to inherit its methods and be treated as a Subject, enabling it to register observers and notify them of changes
+	Count            int
 }
 
+// NewCounter creates and returns a new instance of the Counter struct, initializing the embedded Subject using the NewSubject function from the patterns package
 func NewCounter() Counter {
 	return Counter{patterns.NewSubject(), 0}
 }
 
+// Inc increments the counter's count and notifies all registered observers of the change
 func (c *Counter) Inc() {
 	c.Count++
 	c.Notify()
 }
 
+// Dec decrements the counter's count and notifies all registered observers of the change
 func (c *Counter) Dec() {
 	c.Count--
 	c.Notify()
 }
 
+// CountPrinter is a concrete implementation of the Observer interface, which prints the current count whenever it receives an update notification from the Counter
 type CountPrinter struct {
 	counter *Counter
 }
@@ -33,21 +38,32 @@ func (cp *CountPrinter) Update() {
 	fmt.Println("count updated to ", cp.counter.Count)
 }
 
+var _ patterns.Observer = (*CountPrinter)(nil) // Compile-time assertion to ensure CountPrinter implements the Observer interface
+
+// CounterHistory is a concrete implementation of the Observer interface, which maintains a history of the counter's count values whenever it receives an update notification from the Counter
 type CounterHistory struct {
 	counter *Counter
 	history []int
 }
 
+// Update appends the current count value to the history slice whenever it receives an update notification from the Counter
 func (ch *CounterHistory) Update() {
 	ch.history = append(ch.history, ch.counter.Count)
 }
 
+var _ patterns.Observer = (*CounterHistory)(nil) // Compile-time assertion to ensure CounterHistory implements the Observer interface
+
+// The main function demonstrates the usage of the Counter, CountPrinter, and CounterHistory in an interactive command-line application.
+// It allows the user to increment or decrement the counter and see the updates printed, while also maintaining a history of count values.
 func main() {
+	// Create a new Counter instance, which will serve as the Subject in the Observer pattern
 	counter := NewCounter()
 
+	// Create a new CounterHistory instance and register it as an observer of the counter to track the history of count values
 	history := CounterHistory{&counter, []int{}}
 	counter.Register(&history)
 
+	// Create a new CountPrinter instance and register it as an observer of the counter to print the current count whenever it changes
 	printer := CountPrinter{&counter}
 	counter.Register(&printer)
 	printerRegistered := true
@@ -68,6 +84,7 @@ func main() {
 		case '-':
 			counter.Dec()
 		case 'p':
+			// Toggle the registration of the CountPrinter observer. If it's currently registered, unregister it; if it's currently unregistered, register it.
 			if printerRegistered {
 				counter.Unregister(&printer)
 			} else {

go/04-design-pattern/patterns/observer.go

@@ -1,33 +1,43 @@
 package patterns
 
+// Observer pattern implementation in Go
 type Observer interface {
 	Update()
 }
 
+// Subject interface defines methods for registering, unregistering, and notifying observers
 type Subject interface {
 	Register(o Observer)
 	Unregister(o Observer)
 	Notify()
 }
 
+// Concrete implementation of the Subject interface. Lowercase 'subject' to make it unexported, as it will be created through the NewSubject function.
 type subject struct {
-	observers map[Observer]bool
+	observers map[Observer]bool // Using a map to store observers for efficient add/remove operations
 }
 
+// NewSubject creates and returns a new instance of the subject
 func NewSubject() Subject {
+	// Needs to return a pointer to the subject struct to ensure that the same instance is modified when registering/unregistering observers
 	return &subject{
 		observers: make(map[Observer]bool),
 	}
 }
 
+// Register adds an observer to the subject's set of observers
+// Pointer receiver is used to modify the subject's state (the observers map) when registering an observer
 func (s *subject) Register(o Observer) {
 	s.observers[o] = true
 }
 
+// Unregister removes an observer from the subject's set of observers
+// Pointer receiver is used to modify the subject's state (the observers map) when unregistering an observer
 func (s *subject) Unregister(o Observer) {
 	delete(s.observers, o)
 }
 
+// Notify calls the Update method on all registered observers to notify them of a change
 func (s *subject) Notify() {
 	for o := range s.observers {
 		o.Update()

go/04-design-pattern/patterns/observer_test.go

@@ -6,14 +6,17 @@ import (
 	"gitty.informatik.hs-mannheim.de/steger/pr3-code/go/04-design-pattern/patterns"
 )
 
+// MockObserver is a test implementation of the Observer interface, used to verify that the Notify method correctly calls the Update method on registered observers
 type MockObserver struct {
 	callCount int
 }
 
+// Update increments the callCount to track how many times the Update method has been called on this observer
 func (mo *MockObserver) Update() {
 	mo.callCount++
 }
 
+// Table driven tests for the Subject's Notify method, covering various scenarios of registered and unregistered observers
 func TestSubject_Notify(t *testing.T) {
 	type observer struct {
 		MockObserver