Everywhere is mentioned, Realm needs setters and getters on private field members to work correctly. Accidentially I used public members without setters / getters and the small example worked. Do I miss something (now or in future), where this approach wouldn't work anymore?
Is use Android Studio with io.realm:realm-gradle-plugin:0.91.0
Here is some code:
public class Contact extends RealmObject {
public String phone;
public String mail;
public String person;
}
and later ...
realm.beginTransaction();
Contact contact = realm.createObject(Contact.class);
contact.mail="123";
contact.person="456";
contact.phone="789";
realm.commitTransaction();
final RealmResults<Contact> contacts = realm.where(Contact.class).findAll();
for (Contact c: contacts) {
Log.i(TAG, "mail: " + c.mail);
Log.i(TAG, "person: " + c.person);
Log.i(TAG, "phone: " + c.phone);
}
Emanuele from Realm here. Realm has been supporting public fields with no accessors since 0.88.0 https://realm.io/news/realm-java-0.88.0/
Related
I have a RealmObject, which is used as a temporary data cache only (there will be many entries). I also wrote a static method add() so I can easily add a new entry, but it seems too complicated. Here is the whole class:
public class ExchangePairPriceCache extends RealmObject {
#Index
private String exchangeName;
#Index
private String baseCurrency;
#Index
private String quoteCurrency;
private float price;
private long lastPriceUpdate;
public ExchangePairPriceCache() {
exchangeName = "";
baseCurrency = "";
quoteCurrency = "";
price = 0;
lastPriceUpdate = 0;
}
public ExchangePairPriceCache(String exchangeName, String baseCurrency, String quoteCurrency) {
this.exchangeName = exchangeName;
this.baseCurrency = baseCurrency;
this.quoteCurrency = quoteCurrency;
price = 0;
lastPriceUpdate = 0;
}
public void setPrice(float price) {
// this needs to be called inside a Realm transaction if it's a managed object
this.price = price;
lastPriceUpdate = System.currentTimeMillis();
}
public float getPrice() {
return price;
}
/* static functions */
public static void add(String exchangeName, String baseCurrency, String quoteCurrency, float price) {
Realm realm = Realm.getDefaultInstance();
realm.executeTransaction(r -> {
ExchangePairPriceCache priceCache = r.where(ExchangePairPriceCache.class)
.equalTo("exchangeName", exchangeName)
.equalTo("baseCurrency", baseCurrency)
.equalTo("quoteCurrency", quoteCurrency).findFirst();
if(priceCache != null) {
priceCache.setPrice(price);
} else {
priceCache = new ExchangePairPriceCache(exchangeName, baseCurrency, quoteCurrency);
priceCache.setPrice(price);
ExchangePairPriceCache finalPriceCache = priceCache;
r.insert(finalPriceCache);
}
});
realm.close();
}
public static ExchangePairPriceCache get(String exchangeName, String baseCurrency, String quoteCurrency) {
Realm realm = Realm.getDefaultInstance();
ExchangePairPriceCache priceCache = realm.where(ExchangePairPriceCache.class)
.equalTo("exchangeName", exchangeName)
.equalTo("baseCurrency", baseCurrency)
.equalTo("quoteCurrency", quoteCurrency)
.greaterThan("lastPriceUpdate", System.currentTimeMillis() - TimeUnit.SECONDS.toMillis(10)).findFirst();
if(priceCache != null)
priceCache = realm.copyFromRealm(priceCache);
realm.close();
return priceCache;
}
public static void deleteAll() {
Realm realm = Realm.getDefaultInstance();
realm.executeTransaction(r -> r.delete(ExchangePairPriceCache.class));
realm.close();
}
}
Questions:
Is this a good design (having static functions for ease of use)? I like how I can insert new entries into cache like ExchangePairPriceCache.add("NASDAQ", "AAPL", "USD", 100.5); and delete all with ExchangePairPriceCache.deleteAll() when needed.
How can I simplify add() function? Right now I check if entry already exists and then update the price and if it doesn't, I create a new object and insert it into Realm. I am not able to use updateOrInsert because I don't have unique index for object.
Maybe I am just questioning myself too much and this is all good as it is. But I'd really appreciate some input from experts who use it daily.
You should use a "Repository design pattern" with a DAO object (Data Access Object), to do all your read/ write transactions in realm.
Model class should be a blind copy of objects just holding entities.
Since you do not have any unique identifiers, you can try below
Cache the Exchange pair in Shared preferences file (if they are added earlier or not)
For faster read/writes : Create a temporary unique identifier with a combination of key-value pair that you already have
eg : (exchangeName + baseCurrency + quoteCurrency) - Cast into proper formats to create some unique key with all these values.
This question already has answers here:
Cannot retrieve field values from realm object, values are null in debugger
(5 answers)
Closed 5 years ago.
I need to do a simple query in Realm, retrieve a list of MyModel object and later use it somewhere else in my app. It happens that once I query Realm, each object has null values, but the toString returns the expected values.
Model:
#RealmClass
public class MyModel extends RealmObject implements Serializable {
public static final String KEY_MODEL = "key_myModel";
#PrimaryKey
private int id;
private String myStr;
private int myInt;
//.... getters and setters
#Override
public String toString() {
return "id = " + id
+ "\nmyStr = " + myStr
+ "\nmyInt = " + myInt;
}
}
How do I store the value:
public static void storeModel(MyModel model) {
Realm realm = Realm.getDefaultInstance();
realm.beginTransaction();
realm.copyToRealm(model);
realm.commitTransaction();
}
How do I retrieve the objects:
public static RealmList<MyModel> getNewElementsFromIndex(int indexFrom) {
Realm realm = Realm.getDefaultInstance();
RealmResults<MyModel> allValues = realm.where(MyModel).greaterThan("id", indexFrom).findAll();
RealmList<MyModel> finalList = new RealmList<MyModel>();
finalList.addAll(allValues.subList(0, allValues.size()));
return finalList;
}
When i call getNewElementsFromIndex(value) i get a list of item, but all items in this list have the parameter myStr = null and myInt = 0.
What am I doing wrong?
For managed realm objects, data is not copied to the fields, you obtain them through the proxy getter/setter calls.
Therefore, the fact that fields are null and toString() shows the values is completely expected and well-documented behavior.
To see the values, you have to add watches for the getter methods.
See the documentation.
Say I need to fill a Binary Search Tree with data obtained from Server. Say further that the data coming from server is a json array of nodes
"parts":[{"id":1,"name":"apple"},{"id":12,"name":"orange"},{"id":21,"name":"pen"},{"id":214,"name":"kite"}]//where each {} represents a node
How do I use GSon to read the array of Nodes into my BST?
If you recall a BST has two classes
public class BST{
private Note root;
}
public class Node{
String el;
Node left, right;
}
If BST is too hard, image something simpler
public class MyDataStructure{
private List<Part> partsList;
…
}
public class Part{
String el;
List<String> stuff;
}
How do I populate MyDataStructure with partsList using GSon on android? As a side note, I would rather help solving the MyDataStruction version of the problem.
ok.. you can use this as reference:
define a class pojo
and a Fruit(is the array/list/collection)
the pojo
class Pojo {
#Override
public String toString() {
return "Pojo [parts=" + parts + "]";
}
private List<Fruits> parts;
}
the fruit
class Fruits {
private int id;
private String name;
#Override
public String toString() {
return "[id=" + id + ", name=" + name + "]";
}
}
the implementation
String json = "{\"parts\": [{\"id\":1,\"name\":\"apple\"},{\"id\":2,\"name\":\"pear\"},{\"id\":3,\"name\":\"kiwi\"}]}";
Gson g = new Gson();
Pojo p = g.fromJson(json, Pojo.class);
System.out.println(p);
the MyDataStructure population
add to the pojo a setter getter so you can work with the list, add too setter and getter for the fruit class so you can get the id and the name..
so in the pojo object p you can do p.getList() and iterate over the elements
Something like:
Pojo p = g.fromJson(json, Pojo.class);
System.out.println(p);
for (Fruits f : p.getParts()) {
System.out.println(f.getId());
System.out.println(f.getName());
}
I'm using realm to store my data on Android. Awesome framework! Now the only problem I'm now having is:
I got a array list strings with id's of Countries in my database.
Now I retrieve my Drinks that contains a relationship to countries.
Is there a way that I could to do a query like this:
String [] ids;
realm.where(Drinks.class).equalsTo("country.id", ids);
Something like that?
Or do I really need to do a query to get me all drinks and then filter the list manually?
EDIT:
My classes:
public class Drinks extends RealmObject {
#PrimaryKey
private String id;
private String name;
private Country country;
}
public class Country extends RealmObject {
#PrimaryKey
private String id;
private String name;
}
What you want to do is possible with link queries in theory (searching for "country.id"), however link queries are slow. Also you'd need to concatenate a bunch of or() predicates together, and I would not risk that with a link query.
I would recommend using the following
public class Drinks extends RealmObject {
#PrimaryKey
private String id;
private String name;
private Country country;
#Index
private String countryId;
}
public class Country extends RealmObject {
#PrimaryKey
private String id;
private String name;
}
And when you set the Country in your class, you also set the countryId as country.getId().
Once you do that, you can construct such:
RealmQuery<Drinks> drinkQuery = realm.where(Drinks.class);
int i = 0;
for(String id : ids) {
if(i != 0) {
drinkQuery = drinkQuery.or();
}
drinkQuery = drinkQuery.equalTo("countryId", id);
i++;
}
return drinkQuery.findAll();
Since the Realm database has added RealmQuery.in() with the version 1.2.0
I suggest using something like this.
//Drinks
public class Drinks extends RealmObject {
#PrimaryKey
private String id;
private String name;
private String countryId;
//getter and setter methods
}
//Country
public class Country extends RealmObject {
#PrimaryKey
private String id;
private String name;
//getter and setter methods
}
The code to use inside activity/fragments to retrieve drink list
String[] countryIdArray = new String[] {"1","2","3"} //your string array
RealmQuery<Drinks> realmQuery = realm.where(Drinks.class)
.in("countryId",countryIdArray);
RealmResults<Drinks> drinkList = realmQuery.findAll();
In latest version of Realm 7+, you can use anyOf to match a field against a list of values.
anyOf("name", new String[]{"Jill", "William", "Trillian"})
in older versions, use in instead of anyOf and with kotlin use oneOf instead of in.
see this issue
To match a field against a list of values, use in. For example, to find the names “Jill,” “William,” or “Trillian”, you can use in("name", new String[]{"Jill", "William", "Trillian"}). The in predicate is applicable to strings, binary data, and numeric fields (including dates).
Doc.-> https://realm.io/docs/java/latest#queries
I can't seem to wrap my head around how to setup my class hierarchy for JSON conversion using GSON.
My JSON looks like:
{
"Users": {
"id": 1,
"name": "Jim",
"location": "Huntsville"
}
}
My User List class looks like:
public class UserList {
public static List<User> Users;
#SuppressWarnings("static-access")
public void setUserList(List<User> userList){
this.Users = userList;
}
public List<User> getUserList(){
return Users;
}
}
and lastly a user class that looks like this:
public class User {
private int id;
private String name;
private String location;
public int getId(){
return id;
}
public String getName(){
return name;
}
public String getLocation(){
return location;
}
public String toString(){
return("User: [id=" + id + "], [name=" + name + "], [location=" + location + "]");
}
}
Anyone mind giving me a shove in the right direction? I'd appreciate it!
EDIT:
Forgot to show my parsing code.. (Just reading a sample JSON file from SDCard)
BufferedReader br = new BufferedReader(new FileReader(Environment.getExternalStorageDirectory() + "/user.json"));
UserList userList = gson.fromJson(br, UserList.class);
are you sure your example JSON is correct?
It does not seem to be a list of things, just one user is defined.
Furthermore, your getter and setters for Users, should be following the get/set pattern and be called
public List<User> getUsers()
public void setUsers(List<User> users)
Also, you can follow the Java convention of small case and instruct Gson to use a different casing.
Assuming that you only have one entry of Users in your JSON. This would let you parse the snippit you provided, if you change the Users property into User not a list.
#SerializedName("Users")
private User user;
So if you want a list of users you should find that in the json, this should let you parse it as a list, !note that you need to have objects, which are enclosed, like:
{"users" : [{id:"one"}, ...]}
As pointed out in the comments.