Variable does not exist?

Question

I know I am missing something very small, but I cannot get my head around. This is what I've tried

public class SampleClass {
    public String currentUserId {get;set;}

    public SampleClass(){
       String currentUserId = [SELECT Id, Name FROM User WHERE Id =: UserInfo.getUserId()].Id;
    }

    public static void displayData(){
       System.debug('Current Id: ' +currentUserId);
    }
}

Error:

Line 9: Variable does not exist: currentUserId

Answer 1

You cannot access instance variable(currentUserId) in a static method(displayData).

Either you should declare currentUserId as static:

public Static String currentUserId {get;set;}

Or displayData as non static:

public void displayData(){
    System.debug('Current Id: ' +currentUserId);
}

Also you need not declare currentUserId two times. Avoid declareation inside constructor.

This is the working code:

public class SampleClass {
    public String currentUserId {get;set;}

    public SampleClass(){
        currentUserId = [SELECT Id, Name FROM User WHERE Id =: UserInfo.getUserId()].Id;
    }

    public void displayData(){
        System.debug('Current Id: ' +currentUserId);
    }
}

Note : If you only need current user's id only no need for a query.

You can get by:

currentUserId = UserInfo.getUserId();

Go through Static and Instance Methods, Variables, and Initialization Code for more details.

Answer 2

public static void displayData(){
  System.debug('Current Id: ' +currentUserId);
}

This method is static and you are trying to accessing non-static data member currentUserId in your static function. You cannot access non static members in static context.

Following things can be applied to fix this issue

1. if you declare your variable as static data member, this issue will be fixed.
2. Remove the static keyword from your function