Implementing interfaces in Go - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is an interface in Go?

An interface in Go is a type that defines a set of method signatures. Any type that implements these methods satisfies the interface automatically.

beginner

How does a type implement an interface in Go?

A type implements an interface by having all the methods that the interface requires. There is no explicit declaration needed.

beginner

Given this interface:<br>

type Speaker interface { Speak() string }

<br>How would a struct implement it?

The struct must have a method Speak() that returns a string. For example:<br>

func (p Person) Speak() string { return "Hello!" }

intermediate

Can a pointer receiver implement an interface in Go?

Yes. If the interface method is implemented with a pointer receiver, only pointer types of that struct implement the interface. Value types do not.

beginner

What happens if a type does not implement all methods of an interface?

The type does not satisfy the interface and cannot be assigned to a variable of that interface type.

In Go, how do you declare that a type implements an interface?

A By defining all methods of the interface on the type

B By using the 'implements' keyword

C By embedding the interface in the type

D By importing the interface package

Go uses implicit implementation. If a type has all methods of an interface, it implements it automatically.

If an interface has method Foo(), which of these implements it?

A Type with method Foo()

B Type with method foo() (lowercase f)

C Type with method Foo(int)

D Type with no methods

Method names and signatures must match exactly, including case and parameters.

What is true about pointer receivers and interfaces?

A Interfaces require value receiver methods

B Value types always implement interfaces with pointer receiver methods

C Pointer receiver methods mean only pointer types implement the interface

D Pointer receivers are not allowed in interfaces

If methods have pointer receivers, only pointers to that type implement the interface.

Can a single type implement multiple interfaces?

A No, a type can implement only one interface

B Only if interfaces have no methods

C Only if interfaces are embedded

D Yes, if it has all methods required by each interface

A type can implement any number of interfaces by having the required methods.

What happens if you assign a type that does not implement an interface to a variable of that interface type?

A It works but methods are empty

B Compilation error

C Runtime panic

D It silently ignores missing methods

Go compiler checks interface implementation at compile time and will error if not satisfied.

Explain how a Go type implements an interface and why no explicit declaration is needed.

Think about how Go checks methods rather than declarations.

Describe the difference between pointer receiver and value receiver methods in interface implementation.

Consider which types can call the methods.