/ /

/ /

嵌入式对象 - React Native SDK

Atlas Device SDK 已弃用。有关详细信息，请参阅弃用页面。

创建嵌入式对象

要创建嵌入式对象，请将嵌入式对象的实例分配给父对象的属性：

例子

在以下 CreateContact示例中，我们创建一个带有嵌入式Address对象的新Contact对象。

CreateContact 组件将执行以下操作：

创建表示联系人姓名和解决详细信息的React 状态变量。
通过调用该组件中的 useRealm() 钩子来访问打开的 Realm 实例。
创建执行写事务的组件方法 submitContact()，以根据联系人姓名和地址的 TextInput 值创建新的 Address 嵌入式对象和 Contact 父对象。
在“提交联系人”按钮上添加一个用于调用 submitContact() 的onPress事件。

1 const CreateContact = () => {
2   const [name, setContactName] = useState('');
3   const [street, setStreet] = useState('');
4   const [city, setCity] = useState('');
5   const [country, setCountry] = useState('');
6   const [postalCode, setPostalCode] = useState('');
7   const realm = useRealm();
8 
9   const submitContact = () => {
10     // Create a Contact within a write transaction
11     realm.write(() => {
12       // Create an embedded Address object
13       const address = {
14         street,
15         city,
16         country,
17         postalCode,
18       };
19 
20       realm.create('Contact', {
21         _id: new Realm.BSON.ObjectID(),
22         name,
23         // Embed the address in the Contact object
24         address,
25       });
26     });
27   };
28   return (
29     <View>
30       <TextInput value={name} onChangeText={text => setContactName(text)} />
31       <TextInput value={street} onChangeText={text => setStreet(text)} />
32       <TextInput value={city} onChangeText={text => setCity(text)} />
33       <TextInput value={country} onChangeText={text => setCountry(text)} />
34       <TextInput
35         value={postalCode}
36         onChangeText={text => setPostalCode(text)}
37       />
38       <Button
39         title='Submit Contact'
40         onPress={submitContact}
41       />
42     </View>
43   );
44 };

查询嵌入式对象属性的集合

您可以使用点表示法，根据嵌入式对象的属性值对对象集合进行过滤或排序。

例子

在以下 ContactList 示例中，我们筛选和查询嵌入的 Address 对象。

ContactList 组件将执行以下操作：

通过将 Contact 类传递给 useQuery 钩子，查询所有联系人。
通过在查询"name == 'John Smith'"上传递collection.filtered()来筛选名称为 "John Smith" 的联系人。
使用点表示法检索联系人的街道地址。

1 const ContactList = ({postalCode}) => {
2   // Run the `.filtered()` method on all the returned Contacts to get
3   // contacts with a specific postal code.
4   const contactsInArea = useQuery(
5     Contact,
6     contacts => {
7       return contacts.filtered(`address.postalCode == '${postalCode}'`);
8     },
9     [postalCode],
10   );
11 
12   if (contactsInArea.length) {
13     return (
14       <>
15         <FlatList
16           testID='contactsList'
17           data={contactsInArea}
18           renderItem={({item}) => {
19             <Text>{item.name}</Text>;
20           }}
21         />
22       </>
23     );
24   } else {
25     return <Text>No contacts found in this area.</Text>;
26   }
27 };

1 const ContactList = ({postalCode}: {postalCode: string}) => {
2   // Run the `.filtered()` method on all Contact objects to get
3   // contacts with a specific postal code.
4   const contactsInArea = useQuery(Contact, contacts => {
5     return contacts.filtered(`address.postalCode == '${postalCode}'`);
6   });
7 
8   if (contactsInArea.length) {
9     return (
10       <>
11         <FlatList
12           data={contactsInArea}
13           renderItem={({item}) => {
14             <Text>{item.name}</Text>;
15           }}
16         />
17       </>
18     );
19   } else {
20     return <Text>No contacts found in this area.</Text>;
21   }
22 };

更新嵌入式对象属性

若要更新嵌入式对象中的属性，请在写事务中修改该属性。

例子

在以下 UpdateContact 示例中，我们将更新一个嵌入式 Address 对象的 street 属性。

UpdateContact 组件将执行以下操作：

创建表示联系人新街道地址的 React 状态变量。
通过将 Contact 类传递给 useQuery 钩子来查询所有联系人，并筛选出与作为属性传递到组件的名称相匹配的联系。
通过调用该组件中的 useRealm() 钩子来访问打开的 Realm 实例。
创建用于执行写事务的组件方法 updateStreet()，并将联系人的街道地址设置为 street 状态变量的值。
呈现一个显示并更改 street 状态变量的 TextInput。
在 'Update Street Address' 按钮上添加一个用于调用 updateStreet() 的onPress事件。

1 // Find the contact you want to update
2 const UpdateContact = ({contactId}) => {
3   const [street, setStreet] = useState('');
4   const contact = useObject(Contact, contactId);
5   const realm = useRealm();
6 
7   const updateStreet = () => {
8     // Modify the property of the embedded Address object in a write transaction
9     realm.write(() => {
10       // Update the address directly through the contact
11       contact.address.street = street;
12     });
13   };
14 
15   return (
16     <View>
17       <Text>{contact.name}</Text>
18       <TextInput
19         value={street}
20         onChangeText={setStreet}
21         placeholder='Enter New Street Address'
22       />
23       <Button
24         onPress={updateStreet}
25         title='Update Street Address'
26       />
27     </View>
28   );
29 };

1 // Find the contact you want to update
2 const UpdateContact = ({contactId}: {contactId: Realm.BSON.ObjectId}) => {
3   const [street, setStreet] = useState('');
4   const contact = useObject(Contact, contactId);
5   const realm = useRealm();
6 
7   const updateStreet = () => {
8     // Modify the property of the embedded Address object in a write transaction
9     realm.write(() => {
10       // Update the address directly through the contact
11       contact!.address.street = street;
12     });
13   };
14 
15   return (
16     <View>
17       <Text>{contact!.name}</Text>
18       <TextInput
19         value={street}
20         onChangeText={setStreet}
21         placeholder='Enter New Street Address'
22       />
23       <Button
24         onPress={updateStreet}
25         title='Update Street Address'
26       />
27     </View>
28   );
29 };

覆盖嵌入式对象

要覆盖嵌入式对象，请在写事务中将一方的嵌入式对象属性重新分配给新实例。

例子

在以下 OverwriteContact 示例中，我们覆盖了一个嵌入式Address 对象。

OverwriteContact 组件将执行以下操作：

创建代表联系人新地址的 React 状态变量。
通过将 Contact 类传递给 useQuery 钩子来查询所有联系人，并筛选出与作为属性传递到组件的名称相匹配的联系。
通过调用该组件中的 useRealm() 钩子来访问打开的 Realm 实例。
创建用于执行写事务的组件方法 updateAddress()，并创建一个新的 Address 对象来覆盖 Contact 对象中的现有地址。
呈现 TextInput 元件，显示并变更新地址的状态变量。
在 'Overwrite Address' 按钮上添加一个用于调用 updateAddress() 的onPress事件。

1 const OverwriteContact = ({contactId}) => {
2   const [street, setStreet] = useState('');
3   const [city, setCity] = useState('');
4   const [country, setCountry] = useState('');
5   const [postalCode, setPostalCode] = useState('');
6   const contact = useObject(Contact, contactId);
7   const realm = useRealm();
8 
9   const updateAddress = () => {
10     realm.write(() => {
11       // Within a write transaction, overwrite the embedded object with the new address
12       const address = {
13         street,
14         city,
15         country,
16         postalCode,
17       };
18 
19       contact.address = address;
20     });
21   };
22   return (
23     <View>
24       <Text>{contact.name}</Text>
25       <Text>Enter the new address:</Text>
26       <TextInput
27         value={street}
28         onChangeText={setStreet}
29         placeholder='Street'
30       />
31       <TextInput value={city} onChangeText={setCity} placeholder='City' />
32       <TextInput
33         value={country}
34         onChangeText={setCountry}
35         placeholder='Country'
36       />
37       <TextInput
38         value={postalCode}
39         onChangeText={setPostalCode}
40         placeholder='Postal Code'
41       />
42       <Button
43         onPress={updateAddress}
44         title='Overwrite Address'
45       />
46     </View>
47   );
48 };

1 const OverwriteContact = ({
2   contactId,
3 }: {
4   contactId: Realm.BSON.ObjectId;
5 }) => {
6   const [street, setStreet] = useState('');
7   const [city, setCity] = useState('');
8   const [country, setCountry] = useState('');
9   const [postalCode, setPostalCode] = useState('');
10   const contact = useObject(Contact, contactId);
11   const realm = useRealm();
12 
13   const updateAddress = () => {
14     realm.write(() => {
15       // Within a write transaction, overwrite the embedded object with the new address
16       const address = {
17         street,
18         city,
19         country,
20         postalCode,
21       };
22 
23       contact!.address = address;
24     });
25   };
26 
27   return (
28     <View>
29       <Text>{contact!.name}</Text>
30       <Text>Enter the new address:</Text>
31       <TextInput
32         value={street}
33         onChangeText={setStreet}
34         placeholder='Street'
35       />
36       <TextInput value={city} onChangeText={setCity} placeholder='City' />
37       <TextInput
38         value={country}
39         onChangeText={setCountry}
40         placeholder='Country'
41       />
42       <TextInput
43         value={postalCode}
44         onChangeText={setPostalCode}
45         placeholder='Postal Code'
46       />
47       <Button
48         onPress={updateAddress}
49         title='Overwrite Address'
50       />
51     </View>
52   );
53 };

删除嵌入式对象

Realm 对嵌入式对象使用级联删除要删除嵌入式对象，请删除嵌入式对象的父对象。

例子

在以下 DeleteContact 示例中，我们删除了一个嵌入式对象及其父对象。

DeleteContact 组件将执行以下操作：

通过将 Contact 类传递给 useQuery 钩子，查询所有联系人。
Contact筛选与作为属性传递到组件的名称相匹配的对象。
通过调用该组件中的 useRealm() 钩子来访问打开的 Realm 实例。
创建用于执行写事务的组件方法deleteContact() ，并调用Realm.delete()来删除Contact对象。
在用于调用 deleteContact() 的“Delete Contact”（删除联系人）按钮上添加 onPress 事件。

1 const ContactInfo = ({contactCity, postalCode}) => {
2   const realm = useRealm();
3   const parentsToDelete = useQuery(
4     Contact,
5     contacts => {
6       return contacts.filtered(`address.city == '${contactCity}'`);
7     },
8     [contactCity],
9   );
10   const embeddedToDelete = useQuery(
11     Contact,
12     contacts => {
13       return contacts.filtered(`address.postalCode == '${postalCode}'`);
14     },
15     [postalCode],
16   );
17 
18   const deleteParentObject = () => {
19     realm.write(() => {
20       // Delete all objects that match the filter.
21       // Also deletes embedded objects.
22       realm.delete(parentsToDelete);
23     });
24   };
25 
26   const deleteEmbeddedObject = () => {
27     realm.write(() => {
28       embeddedToDelete.forEach(contact => {
29         // Delete just the embedded object.
30         realm.delete(contact.address);
31       });
32     });
33   };
34 
35   return (
36     <View>
37       <Text testID='contactCityText'>{contactCity}</Text>
38       <Button
39         onPress={deleteParentObject}
40         title='Delete Contact'
41       />
42       <Button
43         onPress={deleteEmbeddedObject}
44         title='Delete Address'
45       />
46     </View>
47   );
48 };

1 type ContactInfoProps = {
2   contactCity: string;
3   postalCode: string;
4 };
5 
6 const ContactInfo = ({contactCity, postalCode}: ContactInfoProps) => {
7   const parentsToDelete = useQuery(Contact, contacts => {
8     return contacts.filtered(`address.city == '${contactCity}'`);
9   });
10   const embeddedToDelete = useQuery(Contact, contacts => {
11     return contacts.filtered(`address.postalCode == '${postalCode}'`);
12   });
13   const realm = useRealm();
14 
15   const deleteParentObject = () => {
16     realm.write(() => {
17       // Delete all objects that match the filter.
18       // Also deletes embedded objects.
19       realm.delete(parentsToDelete);
20     });
21   };
22 
23   const deleteEmbeddedObject = () => {
24     realm.write(() => {
25       embeddedToDelete.forEach(contact => {
26         // Delete just the embedded object.
27         realm.delete(contact.address);
28       });
29     });
30   };
31 
32   return (
33     <View>
34       <Text testID='contactCityText'>{contactCity}</Text>
35       <Button
36         onPress={deleteParentObject}
37         title='Delete Contact'
38       />
39       <Button
40         onPress={deleteEmbeddedObject}
41         title='Delete Address'
42       />
43     </View>
44   );
45 };

后退

UUID

来年

地理空间数据

1	const CreateContact = () => {
2	const [name, setContactName] = useState('');
3	const [street, setStreet] = useState('');
4	const [city, setCity] = useState('');
5	const [country, setCountry] = useState('');
6	const [postalCode, setPostalCode] = useState('');
7	const realm = useRealm();
8
9	const submitContact = () => {
10	// Create a Contact within a write transaction
11	realm.write(() => {
12	// Create an embedded Address object
13	const address = {
14	street,
15	city,
16	country,
17	postalCode,
18	};
19
20	realm.create('Contact', {
21	_id: new Realm.BSON.ObjectID(),
22	name,
23	// Embed the address in the Contact object
24	address,
25	});
26	});
27	};
28	return (
29	<View>
30	<TextInput value={name} onChangeText={text => setContactName(text)} />
31	<TextInput value={street} onChangeText={text => setStreet(text)} />
32	<TextInput value={city} onChangeText={text => setCity(text)} />
33	<TextInput value={country} onChangeText={text => setCountry(text)} />
34	<TextInput
35	value={postalCode}
36	onChangeText={text => setPostalCode(text)}
37	/>
38	<Button
39	title='Submit Contact'
40	onPress={submitContact}
41	/>
42	</View>
43	);
44	};

1	const ContactList = ({postalCode}) => {
2	// Run the `.filtered()` method on all the returned Contacts to get
3	// contacts with a specific postal code.
4	const contactsInArea = useQuery(
5	Contact,
6	contacts => {
7	return contacts.filtered(`address.postalCode == '${postalCode}'`);
8	},
9	[postalCode],
10	);
11
12	if (contactsInArea.length) {
13	return (
14	<>
15	<FlatList
16	testID='contactsList'
17	data={contactsInArea}
18	renderItem={({item}) => {
19	<Text>{item.name}</Text>;
20	}}
21	/>
22	</>
23	);
24	} else {
25	return <Text>No contacts found in this area.</Text>;
26	}
27	};

1	const ContactList = ({postalCode}: {postalCode: string}) => {
2	// Run the `.filtered()` method on all Contact objects to get
3	// contacts with a specific postal code.
4	const contactsInArea = useQuery(Contact, contacts => {
5	return contacts.filtered(`address.postalCode == '${postalCode}'`);
6	});
7
8	if (contactsInArea.length) {
9	return (
10	<>
11	<FlatList
12	data={contactsInArea}
13	renderItem={({item}) => {
14	<Text>{item.name}</Text>;
15	}}
16	/>
17	</>
18	);
19	} else {
20	return <Text>No contacts found in this area.</Text>;
21	}
22	};

1	// Find the contact you want to update
2	const UpdateContact = ({contactId}) => {
3	const [street, setStreet] = useState('');
4	const contact = useObject(Contact, contactId);
5	const realm = useRealm();
6
7	const updateStreet = () => {
8	// Modify the property of the embedded Address object in a write transaction
9	realm.write(() => {
10	// Update the address directly through the contact
11	contact.address.street = street;
12	});
13	};
14
15	return (
16	<View>
17	<Text>{contact.name}</Text>
18	<TextInput
19	value={street}
20	onChangeText={setStreet}
21	placeholder='Enter New Street Address'
22	/>
23	<Button
24	onPress={updateStreet}
25	title='Update Street Address'
26	/>
27	</View>
28	);
29	};

1	// Find the contact you want to update
2	const UpdateContact = ({contactId}: {contactId: Realm.BSON.ObjectId}) => {
3	const [street, setStreet] = useState('');
4	const contact = useObject(Contact, contactId);
5	const realm = useRealm();
6
7	const updateStreet = () => {
8	// Modify the property of the embedded Address object in a write transaction
9	realm.write(() => {
10	// Update the address directly through the contact
11	contact!.address.street = street;
12	});
13	};
14
15	return (
16	<View>
17	<Text>{contact!.name}</Text>
18	<TextInput
19	value={street}
20	onChangeText={setStreet}
21	placeholder='Enter New Street Address'
22	/>
23	<Button
24	onPress={updateStreet}
25	title='Update Street Address'
26	/>
27	</View>
28	);
29	};

1	const OverwriteContact = ({contactId}) => {
2	const [street, setStreet] = useState('');
3	const [city, setCity] = useState('');
4	const [country, setCountry] = useState('');
5	const [postalCode, setPostalCode] = useState('');
6	const contact = useObject(Contact, contactId);
7	const realm = useRealm();
8
9	const updateAddress = () => {
10	realm.write(() => {
11	// Within a write transaction, overwrite the embedded object with the new address
12	const address = {
13	street,
14	city,
15	country,
16	postalCode,
17	};
18
19	contact.address = address;
20	});
21	};
22	return (
23	<View>
24	<Text>{contact.name}</Text>
25	<Text>Enter the new address:</Text>
26	<TextInput
27	value={street}
28	onChangeText={setStreet}
29	placeholder='Street'
30	/>
31	<TextInput value={city} onChangeText={setCity} placeholder='City' />
32	<TextInput
33	value={country}
34	onChangeText={setCountry}
35	placeholder='Country'
36	/>
37	<TextInput
38	value={postalCode}
39	onChangeText={setPostalCode}
40	placeholder='Postal Code'
41	/>
42	<Button
43	onPress={updateAddress}
44	title='Overwrite Address'
45	/>
46	</View>
47	);
48	};

1	const OverwriteContact = ({
2	contactId,
3	}: {
4	contactId: Realm.BSON.ObjectId;
5	}) => {
6	const [street, setStreet] = useState('');
7	const [city, setCity] = useState('');
8	const [country, setCountry] = useState('');
9	const [postalCode, setPostalCode] = useState('');
10	const contact = useObject(Contact, contactId);
11	const realm = useRealm();
12
13	const updateAddress = () => {
14	realm.write(() => {
15	// Within a write transaction, overwrite the embedded object with the new address
16	const address = {
17	street,
18	city,
19	country,
20	postalCode,
21	};
22
23	contact!.address = address;
24	});
25	};
26
27	return (
28	<View>
29	<Text>{contact!.name}</Text>
30	<Text>Enter the new address:</Text>
31	<TextInput
32	value={street}
33	onChangeText={setStreet}
34	placeholder='Street'
35	/>
36	<TextInput value={city} onChangeText={setCity} placeholder='City' />
37	<TextInput
38	value={country}
39	onChangeText={setCountry}
40	placeholder='Country'
41	/>
42	<TextInput
43	value={postalCode}
44	onChangeText={setPostalCode}
45	placeholder='Postal Code'
46	/>
47	<Button
48	onPress={updateAddress}
49	title='Overwrite Address'
50	/>
51	</View>
52	);
53	};

1	const ContactInfo = ({contactCity, postalCode}) => {
2	const realm = useRealm();
3	const parentsToDelete = useQuery(
4	Contact,
5	contacts => {
6	return contacts.filtered(`address.city == '${contactCity}'`);
7	},
8	[contactCity],
9	);
10	const embeddedToDelete = useQuery(
11	Contact,
12	contacts => {
13	return contacts.filtered(`address.postalCode == '${postalCode}'`);
14	},
15	[postalCode],
16	);
17
18	const deleteParentObject = () => {
19	realm.write(() => {
20	// Delete all objects that match the filter.
21	// Also deletes embedded objects.
22	realm.delete(parentsToDelete);
23	});
24	};
25
26	const deleteEmbeddedObject = () => {
27	realm.write(() => {
28	embeddedToDelete.forEach(contact => {
29	// Delete just the embedded object.
30	realm.delete(contact.address);
31	});
32	});
33	};
34
35	return (
36	<View>
37	<Text testID='contactCityText'>{contactCity}</Text>
38	<Button
39	onPress={deleteParentObject}
40	title='Delete Contact'
41	/>
42	<Button
43	onPress={deleteEmbeddedObject}
44	title='Delete Address'
45	/>
46	</View>
47	);
48	};

1	type ContactInfoProps = {
2	contactCity: string;
3	postalCode: string;
4	};
5
6	const ContactInfo = ({contactCity, postalCode}: ContactInfoProps) => {
7	const parentsToDelete = useQuery(Contact, contacts => {
8	return contacts.filtered(`address.city == '${contactCity}'`);
9	});
10	const embeddedToDelete = useQuery(Contact, contacts => {
11	return contacts.filtered(`address.postalCode == '${postalCode}'`);
12	});
13	const realm = useRealm();
14
15	const deleteParentObject = () => {
16	realm.write(() => {
17	// Delete all objects that match the filter.
18	// Also deletes embedded objects.
19	realm.delete(parentsToDelete);
20	});
21	};
22
23	const deleteEmbeddedObject = () => {
24	realm.write(() => {
25	embeddedToDelete.forEach(contact => {
26	// Delete just the embedded object.
27	realm.delete(contact.address);
28	});
29	});
30	};
31
32	return (
33	<View>
34	<Text testID='contactCityText'>{contactCity}</Text>
35	<Button
36	onPress={deleteParentObject}
37	title='Delete Contact'
38	/>
39	<Button
40	onPress={deleteEmbeddedObject}
41	title='Delete Address'
42	/>
43	</View>
44	);
45	};