include ':realm'
project(':realm').projectDir = new File(rootProject.projectDir, '../node_modules/realm/android')
将Realm添加到依赖项中android/app/build.gradle：
// When using Android Gradle plugin 3.0 or higher
dependencies {
implementation project(':realm')
}
// When using Android Gradle plugin lower than 3.0
dependencies {
compile project(':realm')
}
添加导入并链接包MainApplication.java：
import io.realm.react.RealmReactPackage; // add this import
public class MainApplication extends Application implements ReactApplication {
@Override
protected List<ReactPackage> getPackages() {
return Arrays.<ReactPackage>asList(
new MainReactPackage(),
new RealmReactPackage() // add this line
);
}
}
// 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
});
const UpdatedPersonSchema = {
// The schema name is the same, so previous `Person` object
// in the Realm will be updated
name: 'Person',
properties: {
name: 'string',
dog: 'Dog' // new property
}
};
// this will throw because the schema has changed
// and `schemaVersion` is not specified
Realm.open({schema: [UpdatedPersonSchema]});
// this will succeed and update the Realm to the new schema
Realm.open({schema: [UpdatedPersonSchema], schemaVersion: 1});
const PersonSchema = {
name: 'Person',
properties: {
realName: 'string', // required property
displayName: 'string?', // optional property
birthday: {type: 'date', optional: true}, // optional property
}
};
let realm = new Realm({schema: [PersonSchema, CarSchema]});
realm.write(() => {
// optional properties can be set to null or undefined at creation
let charlie = realm.create('Person', {
realName: 'Charlie',
displayName: null, // could also be omitted entirely
birthday: new Date(1995, 11, 25),
});
// optional properties can be set to `null`, `undefined`,
// or to a new non-null value
charlie.birthday = undefined;
charlie.displayName = 'Charles';
// Setting a non-optional property to null will throw `TypeError`
// charlie.realName = null;
});
列表属性
除了存储单个值之外，还可以将属性声明为任何支持的基本类型的列表。这是通过附加[]类型名称来完成的：
const PersonSchema = {
name: 'Person',
properties: {
name: 'string',
testScores: 'double?[]'
}
};
let realm = new Realm({schema: [PersonSchema, CarSchema]});
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);
});
const PersonSchema = {
name: 'Person',
properties: {
// The following property definitions are equivalent
car: {type: 'Car'},
van: 'Car',
}
};
使用对象属性时，需要确保所有引用的类型都存在于用于打开Realm的模式中：
// CarSchema is needed since PersonSchema contains properties of type 'Car'
Realm.open({schema: [CarSchema, PersonSchema]})
.then(/* ... */);
访问对象属性时，可以使用常规属性语法访问嵌套属性：
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;
});
const CarSchema = {
name: 'Car',
properties: {
make: {type: 'string'},
model: {type: 'string'},
drive: {type: 'string', default: 'fwd'},
miles: {type: 'int', default: 0}
}
};
realm.write(() => {
// Since `miles` is left out it defaults to `0`, and since
// `drive` is specified, it overrides the default value
realm.create('Car', {make: 'Honda', model: 'Accord', drive: 'awd'});
});
realm.write(() => {
// Create a book object
realm.create('Book', {id: 1, title: 'Recipes', price: 35});
// Update book with new price keyed off the id
realm.create('Book', {id: 1, price: 55}, true);
});
realm.write(() => {
// Create a book object
let book = realm.create('Book', {id: 1, title: 'Recipes', price: 35});
// Delete the book
realm.delete(book);
// Delete multiple books by passing in a `Results`, `List`,
// or JavaScript `Array`
let allBooks = realm.objects('Book');
realm.delete(allBooks); // Deletes all books
});
發表於 2019-7-10 19:44:00
