How to Create Custom Mapping Between Data Tables and Client Classes
In another post, we describe how data tables in Backendless map to the client-side classes whose instances contain persisted data objects. However, there are scenarios when the default mapping is undesirable. In that case, Backendless client libraries provide an API to override the mapping.
For example, consider the following data table (Restaurant):
Suppose that for some reason the client-side class for the objects in the Restaurant table must be called PlaceToEat. The mapping between the Restaurant table and the PlaceToEat class can be established using the following API:
Backendless.Data.mapTableToClass( "Restaurant", PlaceToEat.class );
Backendless.Data.mapTableToClass("Restaurant", PlaceToEat::class.java)
[[Backendless.shared.data of:[PlaceToEat class]] mapToTableWithTableName:@"Restaurant"];
Backendless.shared.data.of(PlaceToEat.self).mapToTable(tableName: "Restaurant")
Backendless.Data.mapTableToClass('Restaurant', PlaceToEat)
Backendless.Data.mapTableToClass('Location', Location)
Backendless.data.mapTableToClass("Restaurant", PlaceToEat);
Where the PlaceToEat class has the following structure (class’s fields and properties must match the table columns):
import com.backendless.BackendlessUser;
import com.backendless.BackendlessUser;
public class PlaceToEat
{
private String name;
private String objectId;
private String cuisine;
private java.util.List locations;
private BackendlessUser owner;
// skipping getters and setters for brevity
}
import com.backendless.BackendlessUser
class PlaceToEat {
var name: String? = null
var objectId: String? = null
var cuisine: String? = null
var locations: List<Location>? = null
var owner: BackendlessUser? = nul
}
@interface PlaceToEat : NSObject @property (strong, nonatomic) NSString *objectId; @property (strong, nonatomic) NSString *name; @property (strong, nonatomic) NSString *cuisine; @property (strong, nonatomic) BackendlessUser *owner; @end
@objcMembers class PlaceToEat: NSObject {
var objectId: String?
var name: String?
var cuisine: String?
var owner: BackendlessUser?
}
class PlaceToEat {
constructor(props = {}) {
let { name, ownerId, objectId, cuisine, locations } = props
this.name = name
this.objectId = objectId
this.cuisine = cuisine
this.locations = locations
this.ownerId = ownerId
}
// skipping getters and setters for brevity
}
class Location {
constructor(props = {}) {
const { streetAddress, country, objectId, updated, created, ownerId, city, phoneNumber, menu } = props
this.objectId = objectId
this.streetAddress = streetAddress
this.country = country
this.updated = updated
this.created = created
this.ownerId = ownerId
this.city = city
this.phoneNumber = phoneNumber
this.menu = menu
}
// skipping getters and setters for brevity
}
import 'package:backendless_sdk/backendless_sdk.dart';
@reflector
class PlaceToEat {
String name;
String objectId;
String cuisine;
List locations;
BackendlessUser owner;
}
It is recommended that mapTableToClass method is called right after the initApp method, that is before any other API which fetches data from the server.