GoLang Tutorial - Value or Pointer Receiver

There are two reasons to use a pointer receiver.

1. The first is so that the method can modify the value that its receiver points to.
2. The second is to avoid copying the value on each method call. This can be more efficient if the receiver is a large struct, for example.

In the following example, both scale and size are with receiver type *Point, even though the size method does not modify any elements of the Point struct receiver.

The code: pointer-receiver.go

Methods with pointer receivers can modify the value to which the receiver points (as scale does here). Since methods often need to modify their receiver, pointer receivers are more common than value receivers.

Try removing the * from the declaration of the scale function on line 12 and observe how the program's behavior changes:

// func (p *Point) scale(s float64) { ==>
func (p Point) scale(s float64) {
	p.x = p.x * s 
	p.y = p.y * s
}

Output:

before scaling: = &{x:3 y:4}, size: 5
after scaling: &{x:3 y:4}, size: 5

With a value receiver, the scale method operates on a copy of the original Point value. (This is the same behavior as for any other function argument.) The scale method must have a pointer receiver to change the Point value declared in the main function.

Go Tutorial

1. GoLang Tutorial - HelloWorld
2. Calling code in an external package & go.mod / go.sum files
3. Workspaces
4. Workspaces II
5. Visual Studio Code
6. Data Types and Variables
7. byte and rune
8. Packages
9. Functions
10. Arrays and Slices
11. A function taking and returning a slice
12. Conditionals
13. Loops
14. Maps
15. Range
16. Pointers
17. Closures and Anonymous Functions
18. Structs and receiver methods
19. Value or Pointer Receivers
20. Interfaces
21. Web Application Part 0 (Introduction)
22. Web Application Part 1 (Basic)
23. Web Application Part 2 (Using net/http)
24. Web Application Part 3 (Adding "edit" capability)
25. Web Application Part 4 (Handling non-existent pages and saving pages)
26. Web Application Part 5 (Error handling and template caching)
27. Web Application Part 6 (Validating the title with a regular expression)
28. Web Application Part 7 (Function Literals and Closures)
29. Building Docker image and deploying Go application to a Kubernetes cluster (minikube)
30. Serverless Framework (Serverless Application Model-SAM)
31. Serverless Web API with AWS Lambda
32. Arrays vs Slices with an array left rotation sample
33. Variadic Functions
34. Goroutines
35. Channels ("<-")
36. Channels ("<-") with Select
37. Channels ("<-") with worker pools
38. Defer
39. GoLang Panic and Recover
40. String Formatting
41. JSON
42. SQLite
43. Modules 0: Using External Go Modules from GitHub
44. Modules 1 (Creating a new module)
45. Modules 2 (Adding Dependencies)
46. AWS SDK for Go (S3 listing)
47. Linked List
48. Binary Search Tree (BST) Part 1 (Tree/Node structs with insert and print functions)
49. Go Application Authentication I (BasicAuth, Bearer-Token-Based Authentication)
50. Go Application Authentication II (JWT Authentication)