Go methods

Author: Rajeev Kumar Singh

12-structs/01-struct-declaration-initialization/main.go

@@ -6,9 +6,9 @@ import (
 
 // Defining a struct type
 type Person struct {
-	firstName string
-	lastName  string
-	age       int
+	FirstName string
+	LastName  string
+	Age       int
 }
 
 func main() {
@@ -22,13 +22,13 @@ func main() {
 
 	// Naming fields while initializing a struct
 	p2 := Person{
-		firstName: "John",
-		lastName:  "Snow",
-		age:       45,
+		FirstName: "John",
+		LastName:  "Snow",
+		Age:       45,
 	}
 	fmt.Println("Person2: ", p2)
 
 	// Uninitialized fields are set to their corresponding zero-value
-	p3 := Person{firstName: "Robert"}
+	p3 := Person{FirstName: "Robert"}
 	fmt.Println("Person3: ", p3)
 }

12-structs/02-struct-access-fields/main.go

@@ -5,23 +5,23 @@ import (
 )
 
 type Car struct {
-	name, model, color string
-	weightInKg         float64
+	Name, Model, Color string
+	WeightInKg         float64
 }
 
 func main() {
 	c := Car{
-		name:       "Ferrari",
-		model:      "GTC4",
-		color:      "Red",
-		weightInKg: 1920,
+		Name:       "Ferrari",
+		Model:      "GTC4",
+		Color:      "Red",
+		WeightInKg: 1920,
 	}
 
 	// Accessing struct fields using the dot operator
-	fmt.Println("Car name: ", c.name)
-	fmt.Println("Car color: ", c.color)
+	fmt.Println("Car Name: ", c.Name)
+	fmt.Println("Car Color: ", c.Color)
 
 	// Assigning a new value to a struct field
-	c.color = "Black"
+	c.Color = "Black"
 	fmt.Println("Car: ", c)
 }

12-structs/03-pointer-to-struct/main.go

@@ -5,8 +5,8 @@ import (
 )
 
 type Student struct {
-	rollNumber int
-	name       string
+	RollNumber int
+	Name       string
 }
 
 func main() {
@@ -18,9 +18,9 @@ func main() {
 	fmt.Println(ps)
 
 	// Accessing struct fields via pointer
-	fmt.Println((*ps).name)
-	fmt.Println(ps.name) // Same as above: No need to explicitly dereference the pointer
+	fmt.Println((*ps).Name)
+	fmt.Println(ps.Name) // Same as above: No need to explicitly dereference the pointer
 
-	ps.rollNumber = 31
+	ps.RollNumber = 31
 	fmt.Println(ps)
 }

12-structs/04-pointer-to-struct-using-new-function/main.go

@@ -3,17 +3,17 @@ package main
 import "fmt"
 
 type Employee struct {
-	id   int
-	name string
+	Id   int
+	Name string
 }
 
 func main() {
 	// You can also get a pointer to a struct using the built-in new() function
 	// It allocates enough memory to fit a value of the given struct type, and returns a pointer to it
 	pEmp := new(Employee)
 
-	pEmp.id = 1000
-	pEmp.name = "Sachin"
+	pEmp.Id = 1000
+	pEmp.Name = "Sachin"
 
 	fmt.Println(pEmp)
 }

12-structs/05-nested-struct/main.go

@@ -0,0 +1,19 @@
+package main
+
+import (
+	"fmt"
+	"github.com/callicoder/golang-tutorials/12-structs/05-struct-exported-vs-unexported/model"
+)
+
+func main() {
+	c := model.Customer{
+		Id: 1, 
+		Name: "Rajeev Singh",
+	}
+
+	// c.married = true	// Error: can not refer to unexported field or method
+
+	// a := model.address{} // Error: can not refer to unexported name
+	
+	fmt.Println("Programmer = ", c);
+}

12-structs/05-struct-exported-vs-unexported/main/main.go

@@ -0,0 +1,7 @@
+package model
+
+// Unexported struct (only accessible inside package `model`)
+type address struct {
+	houseNo, street, city, state, country string
+	zipCode                               int
+}

12-structs/05-struct-exported-vs-unexported/model/address.go

@@ -0,0 +1,8 @@
+package model
+
+type Customer struct {  // exported struct type
+	Id int				// exported field
+	Name string			// exported field
+	addr address        // unexported field
+	married bool  		// unexported field (only accessible inside package `model`)
+}

12-structs/05-struct-exported-vs-unexported/model/customer.go

@@ -3,8 +3,8 @@ package main
 import "fmt"
 
 type Point struct {
-	x float64
-	y float64
+	X float64
+	Y float64
 }
 
 func main() {
@@ -14,7 +14,7 @@ func main() {
 	fmt.Println("p1 = ", p1)
 	fmt.Println("p2 = ", p2)
 
-	p2.x = 15
+	p2.X = 15
 	fmt.Println("\nAfter modifying p2:")
 	fmt.Println("p1 = ", p1)
 	fmt.Println("p2 = ", p2)

12-structs/06-struct-value-types/main.go

@@ -3,8 +3,8 @@ package main
 import "fmt"
 
 type Point struct {
-	x float64
-	y float64
+	X float64
+	Y float64
 }
 
 func main() {

12-structs/07-struct-equality/main.go

@@ -0,0 +1,23 @@
+package main
+
+import (
+	"fmt"
+	"math"
+)
+
+// Struct type - `Circle`
+type Circle struct {
+	R float64
+}
+
+// Method with receiver `Circle`
+func (c Circle) Area() float64 {
+	return math.Pi * c.R * c.R; 
+}
+
+func main() {
+	c := Circle{5.0}
+
+	fmt.Println("Circle : ", c)
+	fmt.Println("Area of Circle : ", c.Area())
+}

13-methods/01-method-example/main.go

@@ -0,0 +1,31 @@
+package main
+
+import (
+	"fmt"
+	"math"
+)
+
+// Struct type - `Circle`
+type Circle struct {
+	R float64
+}
+
+// Function to calculate the area of Circle
+func Area(c Circle) float64 {
+	return math.Pi * c.R * c.R
+}
+
+/*
+Compare the above function with the corresponding method -
+
+func (c Circle) Area() float64 {
+	return math.Pi * c.R * c.R; 
+}
+*/
+
+func main() {
+	c := Circle{5.0}
+
+	fmt.Println("Circle : ", c)
+	fmt.Println("Area of Circle : ", Area(c))
+}

13-methods/02-methods-are-functions/main.go

@@ -0,0 +1,37 @@
+package main
+
+import (
+	"fmt"
+	"math"
+)
+
+// Struct type - `Circle`
+type Circle struct {
+	R float64
+}
+
+// Struct type - `Rectangle`
+type Rectangle struct {
+	Length, Width float64
+}
+
+// Method with receiver `Circle`
+func (c Circle) Area() float64 {
+	return math.Pi * c.R * c.R; 
+}
+
+// Method with receiver `Rectangle`
+func (r Rectangle) Area() float64 {
+	return r.Length * r.Width;
+}
+
+func main() {
+	c := Circle{5.0}
+	r := Rectangle{7.0, 4.0}
+
+	fmt.Println("Circle : ", c)
+	fmt.Println("Area of Circle : ", c.Area())
+
+	fmt.Println("Rectangle : ", r)
+	fmt.Println("Area of Rectangle : ", r.Area())
+}

13-methods/03-same-method-names-on-different-types/main.go

@@ -0,0 +1,26 @@
+package main
+
+import (
+	"fmt"
+)
+
+type Point struct {
+	X, Y float64
+}
+
+/* 
+  Translates the current Point, at location (X,Y), by dx along the x axis and dy along the y axis 
+  so that it now represents the point (X+dx,Y+dy).
+*/
+func (p *Point) Translate(dx, dy float64) {
+	p.X = p.X + dx
+	p.Y = p.Y + dy
+}
+
+func main() {
+	p := Point{3, 4}	
+	fmt.Println("Point p = ", p)
+
+	p.Translate(7, 9)
+	fmt.Println("After Translate, p = ", p)
+}

13-methods/04-methods-with-pointer-receivers/main.go

@@ -0,0 +1,26 @@
+package main
+
+import (
+	"fmt"
+)
+
+type Point struct {
+	X, Y float64
+}
+
+/* 
+  Translates the current Point, at location (X,Y), by dx along the x axis and dy along the y axis 
+  so that it now represents the point (X+dx,Y+dy).
+*/
+func TranslateFunc(p *Point, dx, dy float64) {
+	p.X = p.X + dx
+	p.Y = p.Y + dy
+}
+
+func main() {
+	p := Point{3, 4}	
+	fmt.Println("Point p = ", p)
+
+	TranslateFunc(&p, 7, 9)
+	fmt.Println("After Translate, p = ", p)
+}