first

course/5-interfaces/exercises/1-interfaces/code.go

@@ -0,0 +1,58 @@
+package main
+
+import (
+	"fmt"
+	"time"
+)
+
+func sendMessage(msg message) {
+	// ?
+}
+
+type message interface {
+	// ?
+}
+
+// don't edit below this line
+
+type birthdayMessage struct {
+	birthdayTime  time.Time
+	recipientName string
+}
+
+func (bm birthdayMessage) getMessage() string {
+	return fmt.Sprintf("Hi %s, it is your birthday on %s", bm.recipientName, bm.birthdayTime.Format(time.RFC3339))
+}
+
+type sendingReport struct {
+	reportName    string
+	numberOfSends int
+}
+
+func (sr sendingReport) getMessage() string {
+	return fmt.Sprintf(`Your "%s" report is ready. You've sent %v messages.`, sr.reportName, sr.numberOfSends)
+}
+
+func test(m message) {
+	sendMessage(m)
+	fmt.Println("====================================")
+}
+
+func main() {
+	test(sendingReport{
+		reportName:    "First Report",
+		numberOfSends: 10,
+	})
+	test(birthdayMessage{
+		recipientName: "John Doe",
+		birthdayTime:  time.Date(1994, 03, 21, 0, 0, 0, 0, time.UTC),
+	})
+	test(sendingReport{
+		reportName:    "First Report",
+		numberOfSends: 10,
+	})
+	test(birthdayMessage{
+		recipientName: "Bill Deer",
+		birthdayTime:  time.Date(1934, 05, 01, 0, 0, 0, 0, time.UTC),
+	})
+}

course/5-interfaces/exercises/1-interfaces/complete.go

@@ -0,0 +1,58 @@
+package main
+
+import (
+	"fmt"
+	"time"
+)
+
+func sendMessage(msg message) {
+	fmt.Println(msg.getMessage())
+}
+
+type message interface {
+	getMessage() string
+}
+
+// don't edit below this line
+
+type birthdayMessage struct {
+	birthdayTime  time.Time
+	recipientName string
+}
+
+func (bm birthdayMessage) getMessage() string {
+	return fmt.Sprintf("Hi %s, it is your birthday on %s", bm.recipientName, bm.birthdayTime.Format(time.RFC3339))
+}
+
+type sendingReport struct {
+	reportName    string
+	numberOfSends int
+}
+
+func (sr sendingReport) getMessage() string {
+	return fmt.Sprintf(`Your "%s" report is ready. You've sent %v messages.`, sr.reportName, sr.numberOfSends)
+}
+
+func test(m message) {
+	sendMessage(m)
+	fmt.Println("====================================")
+}
+
+func main() {
+	test(sendingReport{
+		reportName:    "First Report",
+		numberOfSends: 10,
+	})
+	test(birthdayMessage{
+		recipientName: "John Doe",
+		birthdayTime:  time.Date(1994, 03, 21, 0, 0, 0, 0, time.UTC),
+	})
+	test(sendingReport{
+		reportName:    "First Report",
+		numberOfSends: 10,
+	})
+	test(birthdayMessage{
+		recipientName: "Bill Deer",
+		birthdayTime:  time.Date(1934, 05, 01, 0, 0, 0, 0, time.UTC),
+	})
+}

course/5-interfaces/exercises/1-interfaces/expected.txt

@@ -0,0 +1,8 @@
+Your "First Report" report is ready. You've sent 10 messages.
+====================================
+Hi John Doe, it is your birthday on 1994-03-21T00:00:00Z
+====================================
+Your "First Report" report is ready. You've sent 10 messages.
+====================================
+Hi Bill Deer, it is your birthday on 1934-05-01T00:00:00Z
+====================================

course/5-interfaces/exercises/1-interfaces/readme.md

@@ -0,0 +1,42 @@
+# Interfaces in Go
+
+Interfaces are collections of method signatures. A type "implements" an interface if it has all of the methods of the given interface defined on it.
+
+In the following example, a "shape" must be able to return its area and perimeter. Both `rect` and `circle` fulfill the interface.
+
+```go
+type shape interface {
+  area() float64
+  perimeter() float64
+}
+
+type rect struct {
+    width, height float64
+}
+func (r rect) area() float64 {
+    return r.width * r.height
+}
+func (r rect) perimeter() float64 {
+    return 2*r.width + 2*r.height
+}
+
+type circle struct {
+    radius float64
+}
+func (c circle) area() float64 {
+    return math.Pi * c.radius * c.radius
+}
+func (c circle) perimeter() float64 {
+    return 2 * math.Pi * c.radius
+}
+```
+
+When a type implements an interface, it can then be used as the interface type.
+
+## Assignment
+
+The `birthdayMessage` and `sendingReport` structs have already implemented the `getMessage` methods. The `getMessage` method simply returns a string, and any type that implements the method can be considered a `message`.
+
+First, add the `getMessage()` method as a requirement on the method interface.
+
+Second, complete the `sendMessage` function. It should print a message's `message`, which it obtains through the interface method. Notice that your code doesn't need to worry *at all* about whether a specific message is a `birthdayMessage` or a `sendingReport`!