Go - lesson 3 | HackIndia Skills

Go - lesson 3 | HackIndia Skills | HackIndia

Example

Small store example

Here the handler depends on StudentStore. The mapStore type matches it because it has FindByID with the same signature.

No extra keyword is needed. If the method is missing or has the wrong return type, the code will not compile.

package main

import "fmt"

type Student struct {
	ID   string
	Name string
}

type StudentStore interface {
	FindByID(id string) (Student, bool)
}

type mapStore struct {
	students map[string]Student
}

func (m mapStore) FindByID(id string) (Student, bool) {
	student, ok := m.students[id]
	return student, ok
}

func PrintStudent(store StudentStore, id string) {
	student, ok := store.FindByID(id)
	if !ok {
		fmt.Println("student not found")
		return
	}
	fmt.Println(student.Name)
}

func main() {
	store := mapStore{
		students: map[string]Student{
			"101": {ID: "101", Name: "Asha"},
		},
	}

	PrintStudent(store, "101")
}

Tip

Use fakes

Interfaces make testing easier. You can pass a fake store to a handler instead of connecting to a real database or editing live data.

For a college project, this is enough to show good backend thinking. Your README can say the HTTP layer is tested with a fake store.

type fakeStore struct{}

func (fakeStore) FindByID(id string) (Student, bool) {
	return Student{ID: id, Name: "Test Student"}, true
}

Use interfaces by behavior

One idea

Why it matters

Design the interface

Small store example

Use fakes

Avoid empty interface

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