Go Foundations·Clarity, then concurrency

Structs and interfaces

Go composes with small interfaces and concrete data.

Beginner 14 min read Lesson 8 of 300 Challenge included

What you will be able to do

Accept interfaces, return concrete types.
Keep interfaces near the code that uses them.
Embed to compose behaviour, not to build deep hierarchies.

In plain English

A struct stores data; an interface describes behaviour. Interfaces are satisfied implicitly, so define them where they are consumed, not where types are created. Prefer small interfaces with one or two methods.

store.goGo

type Lesson struct {
    Slug  string
    Title string
}

type LessonStore interface {
    Find(slug string) (Lesson, error)
}

type MemoryStore struct {
    lessons map[string]Lesson
}

func (store MemoryStore) Find(slug string) (Lesson, error) {
    lesson, ok := store.lessons[slug]
    if !ok {
        return Lesson{}, ErrNotFound
    }
    return lesson, nil
}

Your turn

Implement a store

Medium

Implement LessonStore with a MemoryStore that returns ErrNotFound for a missing slug.

GO · starter

func (store MemoryStore) Find(slug string) (Lesson, error) {
}

Check your understanding before moving on.

Knowledge checkQuestion 1

How does a Go type satisfy an interface?

Select an answer to continue

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Next: Goroutines and channels

Lesson 8 of 300 · 0% of course