Background

Getting fancy with Go.

Will like to return a structure from a function.

 

Error

Error – Image

Error – Text

>go run return.Reference.user.User.undeclared.go
# command-line-arguments
.\return.Reference.user.User.undeclared.go:37:2: too many arguments to return
        have (*user.User)
        want ()
.\return.Reference.user.User.undeclared.go:49:25: getUserCurrent() used as value

>

Explanation

1. Error
   • Reads
     • too many arguments to return
       have (*user.User)
       want ()
       .\return.Reference.user.User.undeclared.go:49:25: getUserCurrent() used as value
2.  Explanation
   • Function returns user.User
   • But, it is declared as returning zero parameters

 

 

Code

Original

package main

import (
    "fmt"
    "os/user"
)


func getUserCurrent() {

    /*
        Declare Variables
            objUser as pointer (*) to user.User
    */
    var objUser   *user.User
    var strBuffer string
    var objError  error
    
    /*
        Get current user by accessing the user object
        https://golang.org/pkg/os/user/
        Imported Module os/user
    */
    objUser, objError = user.Current()
    
    if objError!= nil {

        strBuffer = fmt.Sprintf(
                                    "Failed to properly access the %s module\n.  The error is %s", 
                                    "user.Current", objError)                     
    
        fmt.Println(strBuffer);
    
        panic(objError)
    }   

    return (objUser)
    
}


func main(){

    var objUser     *user.User
    var strBuffer   string

    objUser = nil

    objUser= getUserCurrent()

    if (objUser != nil){    
    
        strBuffer = fmt.Sprintf(
                                    "Current User is %s \n", 
                                    objUser.Username)                     

        fmt.Println(strBuffer); 
    }
    
    objUser = nil
    
}

 

Revised

package main

import (
    "fmt"
    "os/user"
)

/*

    Function Name:- getUserCurrent

    Returns:- *user.User 

    Parameters:- None   
*/
func getUserCurrent() *user.User{

    /*
        Declare Variables
            objUser as pointer (*) to user.User
    */
    var objUser   *user.User
    var strBuffer string
    var objError  error
    
    /*
        Get current user by accessing the user object
        https://golang.org/pkg/os/user/
        Imported Module os/user
    */
    objUser, objError = user.Current()
    
    if objError!= nil {

        strBuffer = fmt.Sprintf(
                                    "Failed to properly access the %s module\n.  The error is %s", 
                                    "user.Current", objError)                     
    
        fmt.Println(strBuffer);
    
        panic(objError)
    }   

    // return objUser
    return (objUser)
    
}


func main(){

    var objUser     *user.User
    var strBuffer   string

    objUser = nil


    /*
        Calls:- getUserCurrent
        returns:- objUser
        Parameters :- none
    */
    objUser= getUserCurrent()

    /*
        If returned is not null, display username
    */
    if (objUser != nil){    
    
        strBuffer = fmt.Sprintf(
                                    "Current User is %s \n", 
                                    objUser.Username)                     

        fmt.Println(strBuffer); 
    }
    
    // null out reference
    objUser = nil
    
}

Source Code Control

Github

1. Repository
   • Repository – Folder – golangExercises/function/return/return.Reference/
     Link
     • Files
       • return.Reference.user.User.undeclared.go
         Link
       • return.Reference.user.User.go
         Link

 

Summary

There is a bit of difference in how the return types are indicated in GoLang compared to languages that I am familiar with.

In C, C++, C#, and VB, the return types are indicated to the left of the function.

Whereas, in Go the return type is declared to the right of the function.