How to store Array of Objects in realm-js? - react-native

Question

import Realm from 'realm';
class Cities extends Realm.Object {}
class Users extends Realm.Object {}
Cities.schema = {
name: 'Cities',
properties: {
'name': {
type: 'string'
},
'pincode': {
type: 'int'
}
}
};
Users.schema = {
name: 'Users',
primaryKey: 'id',
properties: {
'id': 'string',
'name': {
type: 'string'
},
'city': {
type: 'list',
objectType: 'Cities'
}
}
};
const schemaList = [Users, Cities];
const realmInstance = new Realm({schema: schemaList});
export default realmInstance;
// pushing a cityObj (that is already present in 'Cities') for a existing User:
onPress={() => this.addCity({name: 'Delhi', pincode: 110004})}
addCity = (cityObj) => {
realm.write(() => {
let user = realm.create('Users', {
'id': 'someUniqueID'
}, true);
user.city.push(cityObj);
});
let cities = realm.objects('Cities');
console.log('cities.length', cities.length);
}
though, trying to update a record in 'Users', The write transaction is writing a new record in Cities table as well creating duplicates. Why so?

Answer 1

Adding to a list will in general create a new object. But you can add a primary key to Cities, create/update the object first and finally push it to the list. Something like:
const Realm = require('realm');
const CitiesSchema = {
name: 'Cities',
primaryKey: 'pincode',
properties: {
'name': {
type: 'string'
},
'pincode': {
type: 'int'
}
}
};
const UsersSchema = {
name: 'Users',
primaryKey: 'id',
properties: {
'id': 'string',
'name': {
type: 'string'
},
'city': {
type: 'list',
objectType: 'Cities'
}
}
};
const schemaList = [UsersSchema, CitiesSchema];
const realm = new Realm({schema: schemaList});
addCity = (cityObj) => {
realm.write(() => {
let city = realm.create('Cities', cityObj, true);
let user = realm.create('Users', {
id: 'someUniqueID',
name: 'Foo Bar'
}, true);
user.city.push(city);
});
let cities = realm.objects('Cities');
console.log('cities.length', cities.length);
}
addCity({name: 'Delhi', pincode: 110004});
addCity({name: 'Delhi', pincode: 110004});