New method `getOrCreate(RealmObject.class, primaryKey)

[beeender]

Suggestion from SO
http://stackoverflow.com/questions/35017640/realmobject-with-primarykey-only

Here I figured out that there is method realm.objectForPrimaryKey(User.self, key: "key") for swift but I did not fund analog in java version.
It would be nice to have in this situation something like realm.getOrCreate(Cat.class, c.id) method. Is there any

[cmelchior]

We actually already have something almost like it createObject(Class clazz, Object primaryKeyValue). It is used internally by the copyOrUpdate methods. It is not public right now because I was a bit concerned how well it would work with composite primary keys + It isn't very type safe. If you put in the wrong value it will crash.

That said, I seen this feature being request a couple of times as well, so maybe it is worth looking into how we can add it to the public API.

[beeender]

What about

<E extends RealmObject> E getOrCreateObject(Class<E> clazz, String primaryKeyValue) { }
<E extends RealmObject> E getOrCreateObject(Class<E> clazz, byte primaryKeyValue) { }
<E extends RealmObject> E getOrCreateObject(Class<E> clazz, short primaryKeyValue) { }
<E extends RealmObject> E getOrCreateObject(Class<E> clazz, int primaryKeyValue) { }
<E extends RealmObject> E getOrCreateObject(Class<E> clazz, long primaryKeyValue) { }

For the composite primary keys, something like, and check the input during run time

<E extends RealmObject> E getOrCreateObject(Class<E> clazz, Map<String, Object> primaryKeyValue) { }

[cmelchior]

Better, but I would hate having to add so many overloaded methods, but yeah it is a trade-off between method count and safety.

[beeender]

just realized we need boxed type as well... which means there are going to be 9 methods....
by allowing null values for primary key, we probably just want methods with boxed types and checking nullability in run time

[cmelchior]

This might be an excellent time to start looking into implementing Lint checks? i.e. we only add:

Realm.createOrGet(Class<? extends RealmObject> clazz, Object primaryKey);

and then use a Lint check on "compiletime".

That would also mean we could get starting exploring what is possible with Lint checks since there is a bunch that would make a lot of sense (checking query parameters is a good one).

[beeender]

Also, we need a method only returns without creating, (return null if it doesn't exist) like:

RealmObject realmObject = Realm.get(Class<? extends RealmObject> clazz, Object primaryKey);

+1 from http://stackoverflow.com/questions/38109905/proper-way-to-get-realm-object-by-its-primary-key-in-android-java

[loudenvier]

I've came up with a helper class which will help get any Realm object by key (returning null if there are no primary key or the object is not found). Here is the code:

public final class Find {
    // shared cache for primary keys
    private static Hashtable<Class<? extends RealmModel>, String> primaryKeyMap = new Hashtable<>();

    private static String getPrimaryKeyName(Realm realm, Class<? extends RealmModel> clazz) {
        String primaryKey = primaryKeyMap.get(clazz);
        if (primaryKey != null)
            return primaryKey;
        RealmObjectSchema schema = realm.getSchema().get(clazz.getSimpleName());
        if (!schema.hasPrimaryKey())
            return null;
        primaryKey = schema.getPrimaryKey();
        primaryKeyMap.put(clazz, primaryKey);
        return primaryKey;
    }

    private static <E extends RealmModel, TKey> E findByKey(Realm realm, Class<E> clazz, TKey key) {
        String primaryKey = getPrimaryKeyName(realm, clazz);
        if (primaryKey == null)
            return null;
        if (key instanceof String)
            return realm.where(clazz).equalTo(primaryKey, (String)key).findFirst();
        else
            return realm.where(clazz).equalTo(primaryKey, (Long)key).findFirst();
    }

    public static <E extends RealmModel> E byKey(Realm realm, Class<E> clazz, String key) {
        return findByKey(realm, clazz, key);
    }

    public static <E extends RealmModel> E byKey(Realm realm, Class<E> clazz, Long key) {
        return findByKey(realm, clazz, key);
    }
}

I've updated the Stack Overflow question: http://stackoverflow.com/questions/38109905/proper-way-to-get-realm-object-by-its-primary-key-in-android-java/38136597#38136597