I've a simple data that i want to persist on firebase.
This data is a domain class for my relational model (i started with a relational model and now im deciding whenever or not migrate to firebase, but for awhile im working with both... or trying to)
To persist a new instance if my class on firebase i need to do:
Map<String, Object> firebase = new HashMap<String, Object>();
firebase.put("raffleDate", this.giveaway.getRaffleDate());
firebase.put("thumbnailUrl", this.giveaway.getThumbnailUrl());
firebase.put("mustFollowList", this.giveaway.getMustFollowList());
firebase.put("owner", this.giveaway.getOwner());
firebase.put("amountFriendsToIndicate", this.giveaway.getAmountFriendsToIndicate());
firebase.put("mediaId", this.giveaway.getMediaId());
((App) getApplication()).getFirebase().child("giveaways").child(this.giveaway.getMediaId()).setValue(firebase);
because besides these fields Giveaway has one last other field which has a circular reference to itself
#ToMany(referencedJoinProperty = "raffle")
#Expose(deserialize = false, serialize = false)
private List<UserOnGiveaway> attendantsTickets;
This field maps the relatioship between user and its giveaways, UserOnGiveaway class has a reference to User and Giveaway so when i try to persist i get a very long non compreensive error that I can just guess is due some stackoverflow because of the circular reference
The thing is I DONT REALLY CARE ABOUT PERSISTING THIS FIELD, in my actual "hybrid" archtecture i'm using firebase only to persist data shared among users, individual user data is being stored locally on android sqlite
So i would like to know is there any way i can annotate this field to force firebase ignore it?
or is there any parameter is can set on firebase call to do it?
PLEASE do not suggest transient as it will also affect my ORM
PLEASE2 do not suggest changes on domain since i'm giving a try to firebase i wont make any structural changes before decide for it.
thanks
You can use the #Exclude annotation on a field or getter/setter method to omit it from serialization with the Firebase SDK.
Related
I am using parceler with realm to pass data from activity to service.
i have few restrictions of realm and parceler
Restrictions
There are some important restrictions to be aware of when using Parceler:
If you model contains a RealmList you need to register a special adapter.
Once an object has been parcelled, it becomes detached from Realm and at this point behaves like an unmanaged object containing a snapshot of the data.Further changes to this object will not be persisted in Realm
for rule 1 i have register a special adapter for it , but for rule 2 i have a doub that at what point realm got deatched
is it at the time of annoting a class i.e. using
#Parcel(value = org.parceler.Parcel.Serialization.BEAN, analyze = { VisitInfo.class })
or at the time of unwrapping and wrapping
RequestInfo requestInfo = Parcels.unwrap(intent.getParcelableExtra("visitData"));
It becomes an unmanaged copy when you call Parcels.wrap() in the first place.
Realm by default expects you to send the primary key of the object over in the intent, and to requery it in the other Activity.
I have a recyclerview which shows a list of students.
All of the students are held in a realmlist in the adapter.
When the user can ask for a data refresh, than the server sends the list of students back to the user.
What i am doing now is to download all of the information from the server , store it in the db , than retrieving it from the database(via realmresults) and than converting the realmresult to realmlist.
My question is how to properly update the UI?
I have seen in the documentation that realmlist have a managed mode where they are updating the ui automatically..
What is this managed mode? What does it means?
How do i use the realmlist to keep it in a managed state?
And what is the right way(aka best practice) to use realmlists?
Note that i cannot hold my information as realmresult directly because im performing some manipulation on the data that i dont want it to be saved.
Managed Object vs. Standalone
The standalone RealmObject/RealmList is created through the Object's constructor or the Realm.copyFromRealm() method. The data accessing in the standalone object won't go through the underline storage engine, instead, it behaves just like normal object. So the standalone object won't be refreshed when data changes. Examples for standalone object:
MyModel myModel = new MyModel(); // Standalone
MyModel model = realm.where(MyModel.class).findFirst(); // This is managed object.
MyModel standaloneModel = realm.copyFromRealm(model); // The returned value is standalone object.
MyList myList = new MyList(); // Standalone
The managed RealmObject/RealmList are accessing data though Realm's underlying storage engine. They are created when you do query from Realm, or the return from the copyToRealm() (and its variant methods). Like:
MyModel model = realm.where(MyModel.class).findFirst();
MyModel model = new MyModel(); // This is a standalone object.
model = realm.copyToRealm(modle); // The returned value is managed by Realm now.
MyList myList = realm.where(MyModel.class).findFirst().getMyList();
How to properly update the UI
The suggestion is using Realm's change listeners. See https://realm.io/docs/java/latest/#notifications
And what is the right way(aka best practice) to use RealmList?
This is a bit confusing, but Realm is introducing RealmCollection into the next major release (v0.89.0). See https://github.com/realm/realm-java/pull/2345.
Note that i cannot hold my information as realmresult directly because im performing some manipulation on the data that i dont want it to be saved.
If the RealmList is in managed mode, the data changes will be saved as well. If you don't want some data to be saved, you could consider to use #Ignore annotation on those fields. See https://realm.io/docs/java/latest/#ignoring-properties
Update on 04072016
RealmList vs. RealmResults:
RealmList is a list of RealmObject saved as a field of a RealmObject. It represents the one-to-many relationship in Realm.
RealmResults is the results of query.
Both of them (if RealmList in managed-mode) will be auto-refreshed when data changes.
You can get a RealmResults from a RealmList by RealmList.where() like:
RealmResults results = myRealmList.where().findAll();
This answer will be a bit out-of-date after Realm v0.89.0 released, because of new RealmCollection.
This question already has answers here:
Cannot retrieve field values from realm object, values are null in debugger
(5 answers)
Closed 5 years ago.
When doing find queries for objects I'm getting "empty" objects (non-null, but not populated). However, in the debugger I can see the data for the object in the object description (see below). I've also verified the data is there using the Realm Browser. I've tried different find queries, querying with filter criteria, using the same Realm object for inserts/queries, using different Realm objects for inserts/queries, refreshing the Realm, etc.
If I Log fields in the RealmObject I see the proper data print out. However, I'm trying to convert these models into other models for use in RxJava per https://realm.io/news/using-realm-with-rxjava/.
Here's some sample code where reproduced the issue. Below that is a screenshot when breaking at verifyRealm.close().
RealmTester realmTester1 = new RealmTester();
realmTester1.setFirstName("Tester1");
realmTester1.setLastName("ABC");
RealmTester realmTester2 = new RealmTester();
realmTester2.setFirstName("Tester2");
realmTester2.setLastName("XYZ");
Realm insertRealm = Realm.getDefaultInstance();
insertRealm.refresh();
insertRealm.beginTransaction();
insertRealm.copyToRealm(realmTester1);
insertRealm.copyToRealm(realmTester2);
insertRealm.commitTransaction();
insertRealm.close();
Realm verifyRealm = Realm.getDefaultInstance();
RealmResults<RealmTester> verifyTesters = verifyRealm.where(RealmTester.class).findAll();
verifyRealm.close();
I have a screenshot of the debugger at: http://i.stack.imgur.com/1UdRr.png
I'm using v0.82.1. Any thoughts on why the models here aren't populating?
The idea behind realm-java is that we are generating Proxy class inherits from user's model class, and override the setters and getters there.
It is totally normal that you see null values for the model's field in the debugger, since the Realm are not setting them. (zero-copy, Realm is trying to reduce the memory usage by managing the data in the native code and sharing them whenever it is possible.)
Because of this, when you want to access a Realm model's field, please always use setters and getters. Checking the generated Proxy class will help you to understand this, it is quite simple actually. It is located in the build directory named like MyModelRealmProxy.java
And also check this section of the documents, it would give you some idea about the standalone object and how to write them to Realm.
THE SCENARIO
I have a class that makes use of a request list set by the user. The request list is stored in SharedPreferences. The dilemma I'm facing is to whether to keep an instance of the request list or to read from SharedPreferences every time the request list is needed (which is very frequent).
Also not that Gson is used to deserialize the object.
The code goes like this:
public List<PrayerTimesCalculator.Time> getDefaultRequestList() {
if (mRequestList != null) return mRequestList;
// Try getting request list from preferences;
Gson gson = new Gson();
String json = mSharedPref.getString(KEY_PREF_REQUEST_LIST, null);
Type listType = new TypeToken<List<Time>>() {
}.getType();
mRequestList = gson.fromJson(json, listType);
if (mRequestList != null) return mRequestList;
// Create default list;
mRequestList = Arrays.asList(
Time.DAWN,
Time.MORNING,
Time.AFTERNOON,
Time.EVENING,
Time.MID_NIGHT);
return mRequestList;
}
THE GOAL
My concern is that if I keep around an instance of the request list, and there are multiple instances of this class, an update to the request list in one instance of the class would not be reflected in the rest of the instances until they are recreated.
Thus, I'm leaning towards reading from SharedPreferences unless there is a better way to keep the request list objected updated in all instances.
THE QUESTION
(1) So, how efficient is it to read the same key from SharedPreferences quite frequently by multiple instances of the object? and (2) Is there a better way to keep the request list objected updated in all instances?
So there are a couple of approaches you can take to this.
First, your object is small - re-reading SharedPreferences thousands of times would hardly be noticeable. It's not like SharedPreferences is on a remote drive or has a "bad connection."
Second, if you don't like that answer, then you need a DAO (Data Access Object). SharedPreferences is a form of this already. It provides a means to store and retrieve data with confidence that you have the most recent data available. But, if you feel like you can improve on it's optimization (because it's generic, and this is your app), then you can provide access to you data through a static object that performs both "read" and "write" operations. This will guarantee that access to the object is done with the most recent data. Of course, you will need to be thread aware, etc. (something that is not always guaranteed by SharedPreferences).
Next, you could persist your data in a database and use Cursors or other built-in or custom DAOs. This requires another level of complexity and a lot of overhead, but is useful when several components of your app might need access to the data, provide updates or needs real-time monitoring of changes because background threads or other objects may make modifications that will change your app behavior or result in UI updates.
Last, you could use more complex data stores like a Content Provider. This is really required for cases where you want/need other apps to access data provided by your app (and your app may also consume the data). That's a complex solution and implementation is well outside the scope of this question.
But I mention it because you seem interested in being certain that frequent reads of SharedPreferences is acceptable. It definitely is acceptable - otherwise there would be something else besides it, databases and Content Providers.
I have started using Parse library recently for Android app. I want to store user contacts using saveEventually and then use the ParseRelation to relate the same to user. As there are multiple contacts mapped to user, I am using below code to handle my save functionality.
ParseRelation relation = ParseUser.getCurrentUser().getRelation(relationshipName);
for(int entityIndex = 0; entityIndex < entities.length;entityIndex++) {
...
entity[entityIndex].saveEventually(); relation.add(entity[entityIndex]);
...
}
ParseUser.getCurrentUser().saveEventually();
Here I am using saveEventually() for each valid entity (ParseObject) and then adding the same to relation. Later once all the objects are added to ParseRelation, at the end I am calling saveEventually() for ParseUser to store all the relationship to Parse.
Is this approach right? I am getting below exception at relation.add(entity[entityIndex]);
All objects in a relation must have object ids.
It seems this suggest some network connectivity issue and ParseRelation is not getting unique objectId for each ParseObject, but I was assuming that this saveEventuall() will handle this scenario well with ParseRelation
Kindly suggest. I am using Parse library version 1.1.11
Thanks.
Any object that's added to a ParseRelation must be saved first. The saveEventually call is non-blocking, so it's unlikely that the object will already have been saved by the time execution reaches the very next line when it's added to a ParseRelation.
Since you need to make sure the object is saved first, you should use saveInBackground instead of saveEventually. Then make sure to add the saved object to the relation from inside saveInBackground's SaveCallback. This will ensure that the object has been saved before being added to the relation.