Interface use cases in Go - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare an interface named Speaker.

Go

type Speaker interface {
	[1]
}

Drag options to blanks, or click blank then click option'

ASpeak(string)

Bspeak()

CSpeak

DSpeak()

Attempts:

3 left

💡 Hint

Common Mistakes

Forgetting parentheses in the method declaration.

Using lowercase method names when uppercase is expected.

The interface method must include parentheses even if it has no parameters, so Speak() is correct.

2fill in blank

medium

Complete the code to make type Dog implement the Speaker interface.

Go

type Dog struct {}

func (d Dog) [1] {
	fmt.Println("Woof!")
}

Drag options to blanks, or click blank then click option'

ASpeak

BSpeak()

Cspeak()

DBark()

Attempts:

3 left

💡 Hint

Common Mistakes

Using a different method name than the interface requires.

Omitting parentheses in the method declaration.

To implement the Speaker interface, Dog must have a method Speak() matching the interface method exactly.

3fill in blank

hard

Fix the error in the code to assign a Dog to a Speaker interface variable.

Go

var s Speaker
var d Dog
s = [1]

Drag options to blanks, or click blank then click option'

A*d

B&d

Cd

DSpeaker(d)

Attempts:

3 left

💡 Hint

Common Mistakes

Assigning a pointer when the method has a value receiver.

Trying to cast the type unnecessarily.

Since Dog implements Speaker by value receiver, assigning d directly works. Using &d would also work if the method had pointer receiver.

4fill in blank

hard

Fill both blanks to create a map of string keys to Speaker interface values, and add a Dog instance.

Go

var animals = map[string][1]{}

animals["dog"] = [2]

Drag options to blanks, or click blank then click option'

ASpeaker

BDog{}

CAnimal{}

DSpeaker{}

Attempts:

3 left

💡 Hint

Common Mistakes

Using a concrete type instead of the interface as map value.

Trying to assign an interface literal which is invalid.

The map value type must be the interface Speaker. To add a Dog, use Dog{} which implements Speaker.

5fill in blank

hard

Fill all three blanks to define an interface, implement it with a Cat struct, and call the method.

Go

type [1] interface {
	[2]()
}

type Cat struct {}

func (c Cat) [2]() {
	fmt.Println("Meow!")
}

func main() {
	var s [1] = Cat{}
	s.[2]()
}

Drag options to blanks, or click blank then click option'

ASpeaker

BSpeak

CSpeak()

DAnimal

Attempts:

3 left

💡 Hint

Common Mistakes

Including parentheses in blanks where only method names are expected.

Using different names for interface and method.

The interface is named Speaker. The method is Speak(), but blanks expect only the method name Speak without parentheses. The method receiver and call use Speak.