[React Native] - Realm Database

Ref:
1. https://docs.mongodb.com/realm-legacy/docs/javascript/latest.html#examples
2. To do list example: https://hellokoding.com/todo-app-with-react-native-realm/

1. Open Realms

//Schema
const PersonSchema = {
  name: 'Person',
  properties: {
    realName:    'string', // required property
    displayName: 'string?', // optional property
    birthday:    {type: 'date', optional: true}, // optional property
  }
};
// Get the default Realm with support for our objects
Realm.open({schema: [Car, Person]})
  .then(realm => {
    // ...use the realm instance here
  })
  .catch(error => {
    // Handle the error here if something went wrong
  });
// Open a realm at another path
Realm.open({
  path: 'anotherRealm.realm',
  schema: [CarSchema]
}).then(/* ... */);

2. Get the current schema version

// Update to to the new schema
Realm.open({schema: [UpdatedPersonSchema], schemaVersion: 1});
//Get current version
const currentVersion = Realm.schemaVersion(Realm.defaultPath);

2. List of properties

realm.write(() => {
  let charlie = realm.create('Person', {
    name: 'Charlie',
    testScores: [100.0]
  });

  // Charlie had an excused absense for the second test and was allowed to skip it
  charlie.testScores.push(null);

  // And then he didn't do so well on the third test
  charlie.testScores.push(70.0);
});

3. Relationship
* To-One Relationship

const PersonSchema = {
  name: 'Person',
  properties: {
    // The following property definitions are equivalent
    car: {type: 'Car'},
    van: 'Car',
  }
};

realm.write(() => {
  const nameString = person.car.name;
  person.car.miles = 1100;

  // create a new Car by setting the property to an object
  // with all of the required fields
  person.van = {make: 'Ford', model: 'Transit'};

  // set both properties to the same car instance
  person.car = person.van;
});

* To-Many Relationships

const PersonSchema = {
  name: 'Person',
  properties: {
    // The following property definitions are equivalent
    cars: {type: 'list', objectType: 'Car'},
    vans: 'Car[]'
  }
}

let carList = person.cars;

// Add new cars to the list
realm.write(() => {
  carList.push({make: 'Honda', model: 'Accord', miles: 100});
  carList.push({make: 'Toyota', model: 'Prius', miles: 200});
});

let secondCar = carList[1].model;  // access using an array index

4. Query

* Get max value in Collection List.
For example: you want to get max of id Person in List. you can do like that

const personList = realm ? realm.objects('Personal') : null;

let idIdx = 0;
if (personList != null && personList.length != 0) {
   idIdx = personList.max('id');
   idIdx++;
}

* Passed para to query
Each subsequent argument is used by the placeholders (e.g. $0, $1, $2, …) in the query.

let person = personList.filtered('id=$0', id);

is updating