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why the Singleton instances have different memory address?

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-3

when I create two instances of a Singleton, the memory address of the instances are
different which confused me. The code as below

import (
 "fmt"
 "sync"
)

type example3 struct 
 name string
 

 var instance3 *example3
 var once sync.Once

 func GetInstance3() *example3 
 once.Do(func() 
 instance3 = new(example3)
 )
 return instance3
 

 func main() 
 e1 := GetInstance3()
 fmt.Printf("address of instance e1: %p n" ,&e1)

 e2 := GetInstance3()
 fmt.Printf("address of instance e2: %p n" ,&e2)
 

and the output as below

address of instance e1: 0xc000006028 
address of instance e2: 0xc000006038

go singleton

share|improve this question

asked Mar 8 at 4:23

sksun27sksun27

41

• 
  
  
  

  
  9
  

  
  
  
  
  
  

  
  
  You're printing the addresses of the variables e1 and e2, which, of course, are different. If you remove the &s, both should have the same value.
  
  – Andy Schweig
  Mar 8 at 4:35
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  finnally, I got it. The %p refer to the value of a point. So I do not need to use & before e1 and e2. Thank you!
  
  – sksun27
  Mar 8 at 6:08
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  sksun27, I don't quite get your wording. All "verbs"—those %something thingies govern how a matching value is formatted, and hence %p merely instructs a fmt.*f function to apply formatting useful for pointers (addresses). Your problem was taking an address of a variable already containing an address you were interested in.
  
  – kostix
  Mar 9 at 8:16
  

  
  
  
  

add a comment | 

-3

when I create two instances of a Singleton, the memory address of the instances are
different which confused me. The code as below

import (
 "fmt"
 "sync"
)

type example3 struct 
 name string
 

 var instance3 *example3
 var once sync.Once

 func GetInstance3() *example3 
 once.Do(func() 
 instance3 = new(example3)
 )
 return instance3
 

 func main() 
 e1 := GetInstance3()
 fmt.Printf("address of instance e1: %p n" ,&e1)

 e2 := GetInstance3()
 fmt.Printf("address of instance e2: %p n" ,&e2)
 

and the output as below

address of instance e1: 0xc000006028 
address of instance e2: 0xc000006038

go singleton

share|improve this question

asked Mar 8 at 4:23

sksun27sksun27

41

• 
  
  
  

  
  9
  

  
  
  
  
  
  

  
  
  You're printing the addresses of the variables e1 and e2, which, of course, are different. If you remove the &s, both should have the same value.
  
  – Andy Schweig
  Mar 8 at 4:35
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  finnally, I got it. The %p refer to the value of a point. So I do not need to use & before e1 and e2. Thank you!
  
  – sksun27
  Mar 8 at 6:08
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  sksun27, I don't quite get your wording. All "verbs"—those %something thingies govern how a matching value is formatted, and hence %p merely instructs a fmt.*f function to apply formatting useful for pointers (addresses). Your problem was taking an address of a variable already containing an address you were interested in.
  
  – kostix
  Mar 9 at 8:16
  

  
  
  
  

add a comment | 

when I create two instances of a Singleton, the memory address of the instances are
different which confused me. The code as below

import (
 "fmt"
 "sync"
)

type example3 struct 
 name string
 

 var instance3 *example3
 var once sync.Once

 func GetInstance3() *example3 
 once.Do(func() 
 instance3 = new(example3)
 )
 return instance3
 

 func main() 
 e1 := GetInstance3()
 fmt.Printf("address of instance e1: %p n" ,&e1)

 e2 := GetInstance3()
 fmt.Printf("address of instance e2: %p n" ,&e2)
 

and the output as below

address of instance e1: 0xc000006028 
address of instance e2: 0xc000006038

go singleton

share|improve this question

asked Mar 8 at 4:23

sksun27sksun27

41

import (
 "fmt"
 "sync"
)

type example3 struct 
 name string
 

 var instance3 *example3
 var once sync.Once

 func GetInstance3() *example3 
 once.Do(func() 
 instance3 = new(example3)
 )
 return instance3
 

 func main() 
 e1 := GetInstance3()
 fmt.Printf("address of instance e1: %p n" ,&e1)

 e2 := GetInstance3()
 fmt.Printf("address of instance e2: %p n" ,&e2)
 

address of instance e1: 0xc000006028 
address of instance e2: 0xc000006038

share|improve this question

asked Mar 8 at 4:23

sksun27sksun27

41

share|improve this question

asked Mar 8 at 4:23

sksun27sksun27

41

asked Mar 8 at 4:23

sksun27sksun27

41

asked Mar 8 at 4:23

sksun27sksun27

41