Realm Exception 'value' is not a valid managed object

问题:

I'm setting a property on a realm object with another realm object which is a different class, however I'm getting the error: 'value' is not avalid managed object.

realmObject.setAnotherRealmObject(classInstance.returnAnotherRealmObjectWithValues()) 

The class instance receives anotherRealmObject constructor and returns it through the method with values from widgets:

public ClassInstance(AnotherRealmObject anotherRealmObject){   mAnotherRealmObject = anotherRealmObject; }  public AnotherRealmObject returnAnotherRealmObjectWithValues(){        mAnotherRealmObject.setId(RandomUtil.randomNumbersAndLetters(5));        mAnotherRealmObject.setName(etName.getText().toString());         return mAnotherRealmObject; } 

I'm creating the new Another Realm Object the right way (I think):

mAnotherRealmObject = mRealmInstance.createObject(AnotherRealmObject.class); 

Is it because I'm returning anotherRealmObject wherein it is already modified because of the passing reference?

回答1:

Upon researching there is a method on realm objects to check if it is valid:

realmObject.isValid(); 

There are two ways I know how to instantiate a realmObject:

RealmObject realmObj = new RealObject(); //Invalid RealmObject realmObj = realmInstance().createObject(RealmClass.class); //Valid 

I was using parceler to pass realmObjects around. Passing a realmObject through parceler and unwrapping it and assigning it to a realmObject variable would make it invalid:

RealmObject realmObj = Parcels.unwrap(data.getParcelableExtra("realmObject")); 

Solution 1 - Pass the unique identifer, then query the realm object:

int uniqueId = Parcels.unwrap(data.getParcelableExtra("uniqueId")); 

Solution 2 - Pass the values, retrieve it, create a realmObject through a realmInstance and assign the values.

//Retrieve values String value1 = Parcels.unwrap(data.getParcelableExtra("value1")); String value2 = Parcels.unwrap(data.getParcelableExtra("value2"));  //Create realmObject 'properly' RealmObject realmObj = realmInstance().createObject(RealmClass.class);  //Assign retrieved values realmObj.setValue1(value1); realmObj.setValue2(value2); 

This way you won't get an invalid realm object.

回答2:

All managed RealmObjects and RealmResults belong to a specific Realm instance. After the corresponding Realm instance gets closed, the RealmObject becomes invalid.

Like below case:

Realm realm = Realm.getInstance(context); realm.beginTransaction(); MyObject obj = realm.createObject(MyObject.class); realm.commitTransaction(); realm.close();  realm = Realm.getInstance(context); realm.beginTransaction(); MyObject obj2 = realm.where(MyObject2.class).findFirst(); obj2.setObj1(obj); // Throws exception, because of the obj's Realm instance is closed. It is invalid now. realm.commitTransaction(); 

You may get some ideas about control the Realm's instance life cycle through this doc

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