Go Methods

From WikiOD

Syntax[edit | edit source]

  • func (t T) exampleOne(i int) (n int) { return i } // this function will receive copy of struct
  • func (t *T) exampleTwo(i int) (n int) { return i } // this method will receive pointer to struct and will be able to modify it

Basic methods[edit | edit source]

Methods in Go are just like functions, except they have receiver.

Usually receiver is some kind of struct or type.

package main

import (
    "fmt"
)

type Employee struct {
    Name string
    Age  int
    Rank int
}

func (empl *Employee) Promote() {
    empl.Rank++
}

func main() {

    Bob := new(Employee)

    Bob.Rank = 1
    fmt.Println("Bobs rank now is: ", Bob.Rank)
    fmt.Println("Lets promote Bob!")

    Bob.Promote()

    fmt.Println("Now Bobs rank is: ", Bob.Rank)

}

Output:

Bobs rank now is:  1
Lets promote Bob!
Now Bobs rank is:  2

Chaining methods[edit | edit source]

With methods in golang you can do method "chaining" passing pointer to method and returning pointer to the same struct like this:

package main

import (
    "fmt"
)

type Employee struct {
    Name string
    Age  int
    Rank int
}

func (empl *Employee) Promote() *Employee {
    fmt.Printf("Promoting %s\n", empl.Name)
    empl.Rank++
    return empl
}

func (empl *Employee) SetName(name string) *Employee {
    fmt.Printf("Set name of new Employee to %s\n", name)
    empl.Name = name
    return empl
}

func main() {

    worker := new(Employee)

    worker.Rank = 1

    worker.SetName("Bob").Promote()

    fmt.Printf("Here we have %s with rank %d\n", worker.Name, worker.Rank)

}

Output:

Set name of new Employee to Bob
Promoting Bob
Here we have Bob with rank 2

Increment-Decrement operators as arguments in Methods[edit | edit source]

Though Go supports ++ and -- operators and the behaviour is found to be almost similar to c/c++, variables with such operators cannot be passed as argument to function.

    package main

    import (
        "fmt"
    )

    func abcd(a int, b int) {
     fmt.Println(a," ",b)
    }
    func main() {
        a:=5
        abcd(a++,++a)
    }

Output: syntax error: unexpected ++, expecting comma or )

Credit:Stack_Overflow_Documentation