Automatically create or update object in database

Question

I have a database class with the following interface:

public Database {
    //returns false if p (its ID) is already available
    //otherwise adds p the the list and returns true
    public boolean create(Person p);

    //returns false if p (its ID) was not found in the list
    //replaces the available Person q (q.ID == p.ID) with p and returns true
    public boolean update(Person p);

    //returns false if p (its ID) was not found in the list
    //marks the available Person q (q.ID == p.ID) as inactive returns true
    public boolean remove(Person p);
}

The Person is immutable and can be identified by a unique id. I have a EditDialog which looks like this:

I wanted to reuse my code and so the EditDialog is used for create a Person or update it. So this dialog is initialized either by a available Person instance (Edit-Operation) or by a new one (Create-Operation).

Because I learned that there is always an evil user I wanted to avoid the following scenario:

• Click "Create Person" button
  • New Person is created in Database
  • EditDialog for new Person is displayed
• Click "Chancel" button
  • Person has to be removed (= marked inactive) from Database
  • EditDialog is disposed
• repeat

Which would lead to many inactive Persons in the Database. So I decided to only create the Person in the Database, if the user clicks the "Save" button. Which leads to two possible scenarios for the Listener of the "Save" button:

1. New Person should be created in Database
2. Person should be updaated in Database

So the code of the Listener looks like the following:

if(!database.create(p) {
    database.update(p);
}

Which is not so pretty in my opinion. The Long and the short of it is, should the Database automatically

• update a Person if it's availabe at invokation of create(Person)?
• create a Person if it's not yet available at invokation of update(Person)?

Or is there another solution/practice I didn't think about?

Answer 1

Your UI should tell the database layer what operation to perform. In the UI, you will obviously have two buttons, one which says "Create new Person" and the other saying, "Edit this Person". So you already know what action needs to be performed.

When you invoke the UI Dialog, pass in this state (Add or Edit) to the dialog. Then, based on the value of this variable, the dialog can call either Database.create() or Database.update() when you click Save.