CRUD — 读取 — Flutter SDK

final luke = realm.find<Person>(lukePrimaryKey);

final people = realm.all<Person>();

final config = Configuration.local([Person.schema, Team.schema]);
final realm = Realm(config);
final heroes = Team(ObjectId(), 'Millenium Falcon Crew', crew: [
  Person(ObjectId(), 'Luke'),
  Person(ObjectId(), 'Leia'),
  Person(ObjectId(), 'Han'),
  Person(ObjectId(), 'Chewbacca')
]);
realm.write(() => realm.add(heroes));
final lukeAndLeia = heroes.crew.query('name BEGINSWITH \$0', ['L']);

realm.write(() {
  realm.addAll([
    (Team(ObjectId(), 'Janitorial Staff',
        eventLog: RealmValue.from({
          '1': {
            'date': DateTime.utc(5622, 8, 18, 12, 30, 0),
            'type': ['work_order', 'maintenance'],
            'summary': 'leaking pipes in control room',
            'priority': 'high',
          },
          '2': {
            'date': DateTime.utc(5622, 9, 18, 12, 30, 0),
            'type': ['maintenance'],
            'summary': 'trash compactor jammed',
            'priority': 'low',
            'comment': 'this is the second time this week'
          }
        }))),
    (Team(ObjectId(), 'IT',
        eventLog: RealmValue.from({
          '1': {
            'date': DateTime.utc(5622, 9, 20, 12, 30, 0),
            'type': ['hardware', 'repair'],
            'summary': 'lightsaber damage to server room',
            'priority': 'high',
          }
        })))
  ]);
  final teams = realm.all<Team>();
  // Use bracket notation to query collection values at the specified path
  final teamsWithHighPriorityEvents =
      // Check any element at that path with [*]
      teams.query("eventLog[*].priority == 'high'");
  print(teamsWithHighPriorityEvents.length); // prints `2`
  final teamsWithMaintenanceEvents =
      // Check for the first element at that path with [FIRST]
      teams.query("eventLog[*].type[FIRST] == 'maintenance'");
  print(teamsWithMaintenanceEvents.length); // prints `1`
  final teamsWithMultipleEvents =
      // Check for collection at that path with matching elements
      // Note that the order must match unless you use ANY or ALL
      teams.query("eventLog[*].type[*] == {'maintenance', 'work_order'}");
  print(
      teamsWithMultipleEvents.length); // prints `0` because order matters
  final teamsWithEventsAsLists =
      // Check the collection type with @type
      teams.query("eventLog[*].type.@type == 'list'");
  print(teamsWithEventsAsLists.length); // prints `2`
});

final config = Configuration.local([Person.schema, Team.schema]);
final realm = Realm(config);
final heroes = Team(ObjectId(), 'Millenium Falcon Crew', crew: [
  Person(ObjectId(), 'Luke', hobbies: [
    'Going to Tashi Station',
    'Fixing the Moisture Vaporators'
  ]),
  Person(ObjectId(), 'Leia', hobbies: [
    'Going on diplomatic missions',
    'Rescuing short stormtroopers'
  ]),
  Person(ObjectId(), 'Han',
      hobbies: ['Shooting first', 'Making fast Kessel Runs']),
  Person(ObjectId(), 'Chewbacca', hobbies: [
    'Fixing the Millenium Falcon',
    'Tearing the arms off of droids'
  ])
]);
realm.write(() => realm.add(heroes));
// Converts the Team object's 'crew' List into a RealmResults<Person>.
final heroesCrewAsResults = heroes.crew.asResults();
final luke = heroesCrewAsResults.query("name == 'Luke'").first;
// Converts Luke's 'hobbies' list into a RealmResults<String>
final lukeHobbiesAsResults = luke.hobbies.asResults();

final team =
    realm.query<Team>('name == \$0', ['Millennium Falcon Crew']).first;
final humanCrewMembers = team.crew.query('name != \$0', ['Chewbacca']);

final listOfNames = ['Luke', 'Leia'];
final matchingRealmObjects =
    realm.query<Person>('name IN \$0', [listOfNames]);

// Find rugs with a chevron pattern
final chevronRugs = realm.query<Rug>("pattern TEXT \$0", ["chevron"]);
// Find rugs with a wool material but not sheep wool
final notSheepWoolRugs = realm.query<Rug>("material TEXT \$0", [" -sheep wool"]);
// Find rugs with a material starting with "co-"
final coRugs = realm.query<Rug>("material TEXT \$0", ["co*"]);

realm.write(() {
  realm.addAll([
    Person(ObjectId(), 'Luke'),
    Person(ObjectId(), 'Leia'),
    Person(ObjectId(), 'Han'),
    Person(ObjectId(), 'Chewbacca')
  ]);
});
final alphabetizedPeople =
    realm.query<Person>('TRUEPREDICATE SORT(name ASC)');
for (var person in alphabetizedPeople) {
  print(person.name);
}
// prints 'Chewbacca', 'Han', 'Leia', 'Luke'

realm.write(() {
  realm.addAll([
    Person(ObjectId(), 'Luke'),
    Person(ObjectId(), 'Luke'),
    Person(ObjectId(), 'Luke'),
    Person(ObjectId(), 'Luke')
  ]);
});
final limitedPeopleResults =
    realm.query<Person>('name == \$0 LIMIT(2)', ['Luke']);
// prints `2`
print(limitedPeopleResults.length);