Summary - Methods
- Go course
- Beginner
- Lesson 80/90
- 4 min
Combine value and pointer receivers to write a bank account.
Methods summary
A method = a function with a receiver: func (t T) Name(). A value receiver works on a copy and is for read-only work; a pointer receiver changes the original and is for large types or types that must not be copied. Methods of embedded types are promoted and can be shadowed; methods that return the receiver can be chained. A String() string method sets fmt's print format.
Method values and expressions
Methods can also be used as functions:
h := &Hesap{}
yatir := h.Yatir // method value: bound to h
yatir(50)
f := (*Hesap).Yatir // method expression: receiver is the first parameter
f(h, 25)
fmt.Println(h.Bakiye) // 75Method values are handy when starting goroutines and passing callbacks: go h.Calis().
Practice Point type
For type Nokta struct{ X, Y int }, write a value-receiver String() (format "(X, Y)") and a pointer-receiver Tasi(dx, dy int). After n := Nokta{1, 2} and n.Tasi(3, 4), print fmt.Println(n).
Starter code
package main
import "fmt"
func main() {
// buraya yaz
}Sample solution
package main
import "fmt"
type Nokta struct{ X, Y int }
func (n Nokta) String() string { return fmt.Sprintf("(%d, %d)", n.X, n.Y) }
func (n *Nokta) Tasi(dx, dy int) {
n.X += dx
n.Y += dy
}
func main() {
n := Nokta{1, 2}
n.Tasi(3, 4)
fmt.Println(n)
}Expected output
(4, 6)
Questions and answers
Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.
1 Which is true of a type's method set?
- *T has both T- and *T-receiver methods; T only T-receiver ones Correct answer
- They are the same
- T contains everything
- *T has only *T-receiver methods
Explanation: This rule matters for interface satisfaction: an interface implemented with pointer-receiver methods is satisfied only by *T.
2 Print format
func (n Nokta) ____() string {
return fmt.Sprintf("(%d, %d)", n.X, n.Y)
}func (n Nokta) String() string {
return fmt.Sprintf("(%d, %d)", n.X, n.Y)
}Explanation: fmt prints types that have a String() string method in their own format.
3 Group summary
| Term | Meaning |
|---|---|
(t T) |
Value receiver |
(t *T) |
Pointer receiver |
Promotion |
Embedded methods |
return s |
Chaining |