Merge pull request #6 from 0bvim/feat/section19

feat/section19

Author: 0bvim

src/udemy/go_ted/section19/anon_func.go

@@ -0,0 +1,28 @@
+package main
+
+import "fmt"
+
+func main() {
+	// not anonymous
+	foo()
+
+	// anonymous
+	func() {
+		fmt.Println("anonymous function")
+	}()
+
+	// anonymous function with param
+	func(s string) {
+		fmt.Println("Anon func showing my name", s)
+	}("Nivi")
+
+	// can assign it to a variable too
+	x := func(s string) {
+		fmt.Println("Anon func showing my name to a func assigned to a variable", s)
+	}
+	x("Thompson")
+}
+
+func foo() {
+	fmt.Println("foo")
+}

src/udemy/go_ted/section19/book_example.go

@@ -0,0 +1,59 @@
+package main
+
+import (
+	"fmt"
+	"log"
+	"strconv"
+)
+
+// link of example https://www.alexedwards.net/blog/interfaces-explained
+
+// this is my implementation of a method that satisfy
+// String() string (fmt.Stringer()) interface
+type Item struct {
+	Type string
+	Name string
+}
+
+func (it Item) String() string {
+	return fmt.Sprintf("Type: %s - Name: %s", it.Type, it.Name)
+}
+
+// Declare a Book type which satisfies the fmt.Stringer interface.
+type Book struct {
+	Title  string
+	Author string
+}
+
+func (b Book) String() string {
+	return fmt.Sprintf("Book: %s - %s", b.Title, b.Author)
+}
+
+// Declare a Count type which satisfies the fmt.Stringer interface.
+type Count int
+
+func (c Count) String() string {
+	return strconv.Itoa(int(c))
+}
+
+// Declare a writeLog function which takes any object that satisfies
+// the fmt.Stringer interface.
+func WriteLog(s fmt.Stringer) {
+	log.Println(s.String())
+}
+
+func main() {
+	// Initialize a Count object and pass it to WriteLog().
+	book := Book{"Alice in Wonderland", "Lewis Carrol"}
+	WriteLog(book)
+
+	// Initialize a Count object and pass it to WriteLog().
+	count := Count(3)
+	WriteLog(count)
+
+	item := Item{
+		Type: "Eletronic",
+		Name: "Notebook",
+	}
+	WriteLog(item)
+}

src/udemy/go_ted/section19/callback.go

@@ -0,0 +1,29 @@
+package main
+
+func main() {
+	println(doMath(41, 1, add))
+	println(doMath(43, 1, subtract))
+	println(doMath(21, 2, multiply))
+	println(doMath(84, 2, division))
+}
+
+// callback function are like function that receive a function pointer as param in 'c'
+func doMath(a, b int, f func(int, int) int) int {
+	return f(a, b)
+}
+
+func add(a, b int) int {
+	return a + b
+}
+
+func subtract(a, b int) int {
+	return a - b
+}
+
+func division(a, b int) int {
+	return a / b
+}
+
+func multiply(a, b int) int {
+	return a * b
+}

src/udemy/go_ted/section19/closure.go

@@ -0,0 +1,36 @@
+package main
+
+import "fmt"
+
+func main() {
+	f := incrementor()
+	fmt.Printf("value: %v\tMem: %v\n", f(), &f)
+	fmt.Printf("value: %v\tMem: %v\n", f(), &f)
+	fmt.Printf("value: %v\tMem: %v\n", f(), &f)
+
+	println("--------------")
+
+	// here, like in 'f' var above the function assigned to the 'g' variable will
+	// be in the same memory place.
+	// so when you call, it will have the same value stored into deeper variable 'x'
+	g := incrementor()
+	fmt.Printf("value: %v\tMem: %v\n", g(), &g)
+	fmt.Printf("value: %v\tMem: %v\n", g(), &g)
+	fmt.Printf("value: %v\tMem: %v\n", g(), &g)
+
+	println("--------------")
+
+	// if you don't assign to a variable it will return initial state of variable 'x'
+	// because it's stored in a different place in memory
+	fmt.Printf("Mem: %v\n", incrementor())
+	fmt.Printf("Mem: %v\n", incrementor())
+	fmt.Printf("Mem: %v\n", incrementor())
+}
+
+func incrementor() func() int {
+	x := 0
+	return func() int {
+		x++
+		return x
+	}
+}

src/udemy/go_ted/section19/defer.go

@@ -0,0 +1,27 @@
+package main
+
+import "fmt"
+
+func main() {
+	// when we use defer (like 'adiar' in pt_br) it's like delay when the action of function will happens
+	{
+		foo()
+		bar()
+	}
+	// in this case foo will be printed after bar
+	{
+		defer foo()
+		bar()
+	}
+}
+
+// func prototype
+// func (r receiver) identifier(p parameter(s)) (r return(s)) { <code? }
+
+func foo() {
+	fmt.Println("foo")
+}
+
+func bar() {
+	fmt.Println("bar")
+}

src/udemy/go_ted/section19/func_rtn.go

@@ -0,0 +1,24 @@
+package main
+
+import . "fmt"
+
+func main() {
+	x := foo()
+	Println(x)
+
+	y := bar()
+	Println(y())
+	Printf("%T\n", foo())
+	Printf("%T\n", bar())
+	Printf("%T\n", y)
+}
+
+func foo() int {
+	return 42
+}
+
+func bar() func() int {
+	return func() int {
+		return 43
+	}
+}

src/udemy/go_ted/section19/function.go

@@ -1,18 +1,64 @@
 package main
 
-import "fmt"
+import (
+	"errors"
+	"fmt"
+	"log"
+)
 
 func main() {
 	foo()
 	foo1("xpto")
+	fmt.Println(foo2("I want"))
+	rtn, err := foo3("I want", " more")
+	if err != nil {
+		log.Fatalf("error while calling foo3: %v", err)
+	}
+	fmt.Println(rtn)
+	fmt.Println(dogYears("Vinicius", 31))
+	fmt.Println(sum(1, 2, 3, 4, 5, 6, 7))
+
+	// unfurling a slice
+	x := []int{1, 2, 3, 4, 5}
+	fmt.Println(sum(x...))
+
 }
 
 // no params and no return
 func foo() {
 	fmt.Println("I am from foo")
 }
 
-// no return
+// 1 param no return
 func foo1(str string) {
 	fmt.Println("I am from foo", str)
 }
+
+// 1 param and 1 return
+func foo2(str string) string {
+	return str + " somenthing"
+}
+
+// 2 param and 2 return
+func foo3(str string, str2 string) (string, error) {
+	if str == "" || str2 == "" {
+		return "", errors.New("something went wrong")
+	}
+	return str + str2, nil
+}
+
+func dogYears(name string, age int) (string, int) {
+	return fmt.Sprint(name, " is this old in dog years "), age * 7
+}
+
+// variadic function
+func sum(ii ...int) int {
+	fmt.Println(ii)
+	fmt.Printf("%T\n", ii)
+
+	n := 0
+	for _, value := range ii {
+		n += value
+	}
+	return n
+}

src/udemy/go_ted/section19/interfaces_polymorph-stringer.go

@@ -0,0 +1,40 @@
+package main
+
+import (
+	"fmt"
+	"log"
+	"strconv"
+)
+
+// basic struct type
+type book struct {
+	title string
+}
+
+// method implemetation
+func (b book) String() string {
+	return fmt.Sprint("Book title: ", b.title)
+}
+
+// basic type
+type count int
+
+// method implementation
+func (c count) String() string {
+	return fmt.Sprint("The number is ", strconv.Itoa(int(c)))
+}
+
+func main() {
+	b := book{
+		title: "Learning to learn",
+	}
+
+	var c count = 42
+
+	logInfo(b)
+	logInfo(c)
+}
+
+func logInfo(s fmt.Stringer) {
+	log.Println("Log from section19:", s.String())
+}

src/udemy/go_ted/section19/methods.go

@@ -0,0 +1,53 @@
+package main
+
+import "fmt"
+
+// simple type example
+type person struct {
+	first string
+}
+
+type secretAgent struct {
+	person
+	ltk bool
+}
+
+// method implementation
+func (p person) speak() {
+	fmt.Println("My name is", p.first)
+}
+
+func (sa secretAgent) speak() {
+	fmt.Println("Im a secret agent", sa.first)
+}
+
+// interface help us to have polymorphism
+// interfaces in Go define a set of method signatures.
+
+type human interface {
+	speak()
+}
+
+// function to receive a parameter of human interface and "speak"
+// when a type implements the called method in interfaces, it are of this interfaces type
+// like secreAgent and person
+
+func saySomething(h human) {
+	h.speak()
+}
+
+func main() {
+	sa1 := secretAgent{
+		person: person{
+			first: "James",
+		},
+		ltk: true,
+	}
+
+	p2 := person{
+		first: "Janny",
+	}
+
+	saySomething(sa1)
+	saySomething(p2)
+}

src/udemy/go_ted/section19/recursion.go

@@ -0,0 +1,13 @@
+package main
+
+func main() {
+	println(factorial(4))
+}
+
+func factorial(n int) int {
+	println("this is n", n)
+	if n == 0 {
+		return 1
+	}
+	return factorial(n-1) * n
+}