＆Struct {}与Struct {}之间的区别

Question

Is there a reason why I should create a struct using &StructName{} instead of Struct{}? I see many examples using the former syntax, even in the Effective Go Page but I really can not understand why.

Additional Notes: I'm not sure whether I explained my problem well with these two approaches so let me refine my question.

I know that by using the & I will recieve a pointer instead of a value however I would like to know why would I use the &StructName{} instead of the StructName{}. For example, is there any benefits of using:

func NewJob(command string, logger *log.Logger) *Job {
    return &Job{command, logger}
}

instead of:

func NewJob(command string, logger *log.Logger) Job {
    return Job{command, logger}
}

Answer 1

Well, they will have different behavior. Essentially if you want to modify state using a method on a struct, then you will need a pointer, otherwise a value will be fine. Maybe an example will be better:

package main
import "fmt"



type test_struct struct {
  Message string
}

func (t test_struct)Say (){
   fmt.Println(t.Message)
}

func (t test_struct)Update(m string){
  t.Message = m; 
}

func (t * test_struct) SayP(){
   fmt.Println(t.Message)
}

func (t* test_struct) UpdateP(m string)  {
  t.Message = m;
}

func main(){
  ts := test_struct{}
  ts.Message = "test";
  ts.Say()
  ts.Update("test2")
  ts.Say() // will still output test

  tsp := &test_struct{}
  tsp.Message = "test"
  tsp.SayP();
  tsp.UpdateP("test2")
  tsp.SayP() // will output test2

}

And you can run it here go playground