AntonStoeckl

// The HandlerFunc type is an adapter to allow the use of
// ordinary functions as HTTP handlers. If f is a function
// with the appropriate signature, HandlerFunc(f) is a
// Handler that calls f.
type HandlerFunc func(ResponseWriter, *Request)

// ServeHTTP calls f(w, r).
func (f HandlerFunc) ServeHTTP(w ResponseWriter, r *Request) {
	f(w, r)
}

AntonStoeckl

package closures

// CustomerService has repo as a protperty
// that will be "enclosed" in the receiver methods
type CustomerService struct {
   repo CustomerRepository
}

// Register is a receiver method that will be used as a closure
func (s *CustomerService) Register(customerName string) error {

AntonStoeckl

package closures_test

import (
   "testing"

   "github.com/matryer/is"

   . "go-bits/magic-with-functions/closures"
)

AntonStoeckl

package closures_test

import (
   "testing"

   "github.com/matryer/is"

   . "go-bits/magic-with-functions/closures"
)

AntonStoeckl

package closures

// IsBiggerThan returns a closure function that is parametrized with the 
// first parameter
func IsBiggerThan(first int) func(second int) bool {
   isBigger := func(second int) bool {
      return second > first
   }

   return isBigger

AntonStoeckl

package basics_test

import (
   "testing"

   "github.com/matryer/is"

   . "go-bits/magic-with-functions/basics"
)

AntonStoeckl

package basics

// CompareFn is a function type
type CompareFn func(first, second int) bool

// OtherCompare is a higher order function that compares two integers via a 
// function that is passed in as the third parameter using a function type 
// annotation, so the function type is used to annotate the type of the 
// parameter
func OtherCompare(first, second int, compareFn CompareFn) bool {

AntonStoeckl

package basics_test

import (
	"testing"

	"github.com/matryer/is"

	. "go-bits/magic-with-functions/basics"
)

AntonStoeckl

package basics

// IsBigger is a plain function that compares two integers
// and return true if the first is bigger than the second ;-)
func IsBigger(first, second int) bool {
   return first > second
}

// Compare is a higher order function that compares two integers via a function
// that is passed in as the third parameter using explicit annotation,

AntonStoeckl

func (h *SomeHandler) (w ResponseWriter, r *Request) {
   // ...
}