Question

I have these two classes

@DatabaseTable
public class User {
    @DatabaseField(generatedId=true)
    private int _id;
    @DatabaseField
    private String name;
    @DatabaseField
    private String password;
    @DatabaseField(canBeNull = false, foreign = true, unique = true)
    private Item item;

and

@DatabaseTable
public class Item {
    @DatabaseField(generatedId=true)
    private int _id;
    @DatabaseField
    private String name;

I would like to query a single user from the database using a platform since they are unique, how do I go about this?

Answer 1

I’m not sure what a “platform” is. To query for a User that matches a particular Item you would do something like:

List<User> results = userDao.queryBuilder().where().eq("item", item).query();

This returns a list of results. If there will be only one then you could do

QueryBuilder<User, Integer> qb = userDao.queryBuilder();
qb.where().eq("item", item);
User user = qb.queryForFirst();

It is a good pattern to define the column name using a public final static String:

@DatabaseTable
public class User {
    public final static String ITEM_COLUMN_NAME = "item";
    ...
    @DatabaseField(columnName = ITEM_COLUMN_NAME, canBeNull = false,
         foreign = true, unique = true)
    private Item item;

Then your query can do:

...eq(User.ITEM_COLUMN_NAME, item)

Notice that although the actual field stored is an integer, the eq(...) method is smart enough to take an item and extract its id field from it.