Develop Reference

Remove duplication from an array of objects

I have an object like below,
class LocationData{
String time;
String name;
String address;
}
for this object i have created getter setter.
By using service i fill this above model and save into room database.
whenever user open my app i just update the room database data to server using API.
Now sometimes the time duplication occurred. How to remove the object from array based on time. time should be unique.

You can use the extension function distinctBy. If you have an array of LocationData objects called allLocations it would be
val distinctLocations = allLocations.distinctBy { it.time }
Note distinctLocations will be a List; if you want it to be an array, use toTypedArray()

How could I insert new data to array without key in Firebase

I have an existing array that I created locally and import to Firebase and my array looks like this.
These both elements are objects created that have some many information related to appointments.
Now i am trying to create a new element with the same form, for example:
2--
|__ And the object I have created in my app
I have only managed or eliminate the rest of the elements (with setValue(object))
Appointment newAppointment = new Appointment.Builder()
.fechacita(dateSelected)
.horacita(hourSelected)
.usertoken(mAuthManager.getCurrentUserId())
.oficina(centerSelected)
.build();
mDatabaseRef.child("LISTACITAS").setValue(newAppointment);
or create it with an ID that when recovering the data causes a crash in the application due to the deserialization of the objects that are not equal.
The Appointment object that I want to insert is
public class Appointment implements Parcelable {
private String fechacita;
private String horacita;
private Office oficina;
private String userID;
.....
}
The class is a normal Parcelable class that generates an object with her builder.
Please some help...

try this code
mDatabaseRef.push().setValue(incidentReportUser)
Write it this way (push() adds values instead of overriding).
Ans from here
UPDATE 1
if you want a series in key, not some random value, try this:
get the last key in the list using
Query dbQry = mDatabaseRef.orderByKey().limitToLast(1);
dbQry.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot dataSnapshot) {
int key = Integer.parseInt(dataSnapshot.getKey());
//Increment the key and add the object here using the earlier method
}
#Override
public void onCancelled(DatabaseError databaseError) {
}
}
I have not checked this as of now, but you could get the idea

Confuse on dealing with relations between objects using Android Room

When using the android data-persistent library Android Room ,how can I directly insert the Comment Object into the database including all the field value, and how can I query all the value out as a Comment Object?
As I know, I can not use the Comment Object as a Entity in Room directory, because of the field replyComment is also a Comment Object. And I can not query out a Comment Object even I define a POJO using the #Relations annotation either because of the one-to-one relations and one-to-many relations all included in the Comment Object.
Is there any other way except changing the Comment Model definition, such as using foreign key, making a effect on insert action and query action?
public class Comment {
public String content;
public String id;
public Comment replyComment;
public User user;
public List<ImageMedia> images;
}
public class User{
public String id;
public String name;
}
public class ImageMedia{
public String key;
public String url;
}

Is there any other way except changing the Comment Model definition
No. You would need to create a set of entities that model the database structure, where children have foreign key columns pointing back to their parents:
CommentEntity has a foreign key back to CommentEntity for the reply
CommentEntity has a foreign key back to UserEntity
ImageMediaEntity has a foreign key back to CommentEntity

Save linked objects Primary key value already exists Relationships

I have just started to use RealmDB and cannot figure out how to save linked object correctly, to implement a sort of foreign key
Here is my main User model.
public class UserModel extends RealmObject {
#PrimaryKey
public Long id;
public String firstName;
public String lastName;
public UserSettings userSettingsModel;
}
UserSettings Model is defined as follows.
public class UserSettingsModel extends RealmObject {
#PrimaryKey
private Long id;
public String email;
public RealmList<Car> cars;
}
And Car is a model itself.
public class Car extends RealmObject {
#PrimaryKey
private Long id;
public String model;
}
The problem is that when I am trying to save UserModel it tries to recreate all objects assigned to it. So before I saving user model I have already creates some Car objects.
I don't need to create them, but to reference like the foreign key in SQL databases. And when I am retrieving a user from the database it should automatically load all related data by primary keys.
Is it possible to achieve such behavior using Realm ?

Thanks for help. Solved this problem by using the copyToRealmOrUpdate method instead of copyToRealm.

You should create a managed object using realm.createObject(clazz, pkValue); if it doesn't exist yet, then set it as value or add it to the RealmList that you get another managed object.
You can also create managed objects from unmanaged objects with copyToRealmOrUpdate() (if the object has a primary key).
And when I am retrieving a user from the database it should automatically load all related data by primary keys.
The RealmList allows access to the related objects, and in fact, is also queryable by calling .where() on it. However, this is not based on primary keys. That feature is tracked under "computed fields".

Practical use of #Ignore in Realm?

I've been trying to add Realm in my Android app. Their docs are pretty well explained & easy to follow. But it fails to explain this one particular area. I'm unable to figure out the practical use for the #Ignore annotation. I know that fields under this annotation are not persisted.
Can someone please share a few use cases. Also I wanted to know the scope of such fields. I mean, if I set an #Ignore field to some value, would that value be available to the other classes in my app for that particular launch session. If yes, then how do we access it? If no (which I guess is the case), then why do we need such a field anyway?
I've searched here and on web but couldn't find the relevant information. If out of my ignorance, I've missed upon some resource, please guide me to it.
Thanks.

Accordingly to the official documentation (see https://realm.io/docs/java/latest/) #Ignore is useful in two cases:
When you use GSON integration and your JSON contains more data than you want to store, but you still would like to parse it, and use right after.
You can't create custom getters and setter in classes extending RealmObject, since they are going to be overridden. But in case you want to have some custom logic anyway, ignored fields can be used as a hack to do that, because Realm doesn't override their getter & setters. Example:
package io.realm.entities;
import io.realm.RealmObject;
import io.realm.annotations.Ignore;
public class StringOnly extends RealmObject {
private String name;
#Ignore
private String kingName;
// custom setter
public void setKingName(String kingName) { setName("King " + kingName); }
// custom getter
public String getKingName() { return getName(); }
// setter and getter for 'name'
}
Ignored fields are accessible only from the object they were set in (same as with regular objects in Java).
UPDATE: As the #The-null-Pointer- pointed out in the comments the second point is out of date. Realm now allows having custom getters and setters in Realm models.

Here's a couple of real-world use cases:
1 - Get user's fullname:
public class User extends RealmObject {
private String first;
private String last;
#Ignore
private String fullName;
public String getFullName() {
return getFirst() + " " + getLast();
}
Get JSON representation of object:
public class User extends RealmObject {
private String first;
private String last;
#Ignore
private JSONObject Json;
public JSONObject getJson() {
try {
JSONObject dict = new JSONObject();
dict.put("first", getFirst());
dict.put("last", getLast());
return dict;
} catch (JSONException e) {
// log the exception
}
return null;
}

I've found it useful to define field names for when I am querying. For example
User.java
public class User extends RealmObject {
#Index
public String name;
#Ignore
public static final String NAME = "name";
}
And then later on I can do something like:
realm.where(User.class).equalTo(User.NAME, "John").findFirst();
This way if the schema changes from say name to id I don't have to hunt down every occurrence of "name".

Please see the the official documentation about #Ignore annotation:
The annotation #Ignore implies that a field should not be persisted to disk. Ignored fields are useful if your input contains more fields than your model, and you don’t wish to have many special cases for handling these unused data fields.