React Native应用中的Parse.Query详解与示例

20min
在 React Native 中解析查询食谱
介绍
我们已经看到如何使用 Parse.Query 来从 Back4App 检索单个 get。还有许多其他方法可以使用 Parse.Object 从 Parse.Query 检索数据 - 您可以一次检索多个对象，对您希望检索的对象使用条件等等。
在本指南中，您将深入了解 Parse.Query 类，并查看您可以用来构建查询的所有方法。您将使用一个简单的数据库类和一些模拟数据，通过 Back4App 的 Javascript 控制台执行查询。
先决条件
要完成本教程，您需要：
一个 在 Back4App 上创建的应用.
目标
探索 Parse.Query 类的不同方法。
Parse.Query 类
在 Parse 上的任何查询操作都使用 Parse.Query 对象类型，这将帮助您在整个应用程序中从 Back4App 中检索特定数据。要创建一个新的 Parse.Query, 您需要将所需的 Parse.Object 子类作为参数传递，这个子类将包含您的查询结果。
重要的是要知道 Parse.Query 只有在调用检索方法（如 Parse.Query.find 或 Parse.Query.get）后才会解析，因此可以设置查询并在实际调用之前链接多个修饰符。
您可以在官方文档中阅读更多关于 Parse.Query 类的信息，在这里查看官方文档。
在 Back4App 上使用 JS 控制台
在您的 Back4App 应用程序的仪表板中，您会找到一个非常有用的 API 控制台，您可以直接在其中运行 JavaScript 代码。在本指南中，您将使用它来存储和查询来自 Back4App 的数据对象。在您的应用程序主仪表板中，转到 Core->API Console->JS Console.﻿
﻿
保存您的数据对象
要在本指南上运行查询，您首先需要为您的应用填充一些数据。让我们创建一个名为 Profile 的示例类，它模拟一个社交媒体个人资料类，使用名人姓名和以下字段：
字符串类型姓名:
日期类型生日:
数字（整数）类型好友数量:
数组（字符串数组）类型最爱食物:
数组（数字数组）类型幸运数字:
地理点类型登录位置:
可空指针类型高级会员, 与一个包含字符串的 会员 类相关，包含字符串 姓名 和日期 到期日期字段。
这里是 Parse.Object 类的创建代码，所以请在您的 API 控制台中运行它:
JS
1	// Add Profile objects and create table
2	// Adam Sandler
3	let Profile = new Parse.Object('Profile');
4	Profile.set('name', 'Adam Sandler');
5	Profile.set('birthDay', new Date('09/09/1966'));
6	Profile.set('friendCount', 2);
7	Profile.set('favoriteFoods', ['Lobster', 'Bread']);
8	Profile.set('luckyNumbers', [2, 7]);
9	Profile.set('lastLoginLocation', new Parse.GeoPoint(37.38412167489413, -122.01268034622319));
10	await Profile.save();
11	
12	// Britney Spears
13	Profile = new Parse.Object('Profile');
14	Profile.set('name', 'Britney Spears');
15	Profile.set('birthDay', new Date('12/02/1981'));
16	Profile.set('friendCount', 52);
17	Profile.set('favoriteFoods', ['Cake', 'Bread']);
18	Profile.set('luckyNumbers', [22, 7]);
19	Profile.set('lastLoginLocation', new Parse.GeoPoint(37.38412167489413, -122.01268034622319));
20	await Profile.save();
21	
22	// Carson Kressley
23	Profile = new Parse.Object('Profile');
24	Profile.set('name', 'Carson Kressley');
25	Profile.set('birthDay', new Date('11/11/1969'));
26	Profile.set('friendCount', 12);
27	Profile.set('favoriteFoods', ['Fish', 'Cookies']);
28	Profile.set('luckyNumbers', [8, 2]);
29	Profile.set('lastLoginLocation', new Parse.GeoPoint(37.38412167489413, -122.01268034622319));
30	await Profile.save();
31	
32	// Dan Aykroyd
33	// Creates related object Membership for this user only
34	let Membership = new Parse.Object('Membership');
35	Membership.set('name', 'Premium');
36	Membership.set('expirationDate', new Date('10/10/2030'))
37	await Membership.save();
38	Profile = new Parse.Object('Profile');
39	Profile.set('name', 'Dan Aykroyd');
40	Profile.set('birthDay', new Date('07/01/1952'));
41	Profile.set('friendCount', 66);
42	Profile.set('favoriteFoods', ['Jam', 'Peanut Butter']);
43	Profile.set('luckyNumbers', [22, 77]);
44	Profile.set('lastLoginLocation', new Parse.GeoPoint(37.38412167489413, -122.01268034622319));
45	Profile.set('premiumMembership', Membership);
46	await Profile.save();
47	
48	// Eddie Murphy
49	Profile = new Parse.Object('Profile');
50	Profile.set('name', 'Eddie Murphy');
51	Profile.set('birthDay', new Date('04/03/1961'));
52	Profile.set('friendCount', 49);
53	Profile.set('favoriteFoods', ['Lettuce', 'Pepper']);
54	Profile.set('luckyNumbers', [6, 5]);
55	Profile.set('lastLoginLocation', new Parse.GeoPoint(-27.104919974838154, -52.61428045237739));
56	await Profile.save();
57	
58	// Fergie
59	Profile = new Parse.Object('Profile');
60	Profile.set('name', 'Fergie');
61	Profile.set('birthDay', new Date('03/27/1975'));
62	Profile.set('friendCount', 55);
63	Profile.set('favoriteFoods', ['Lobster', 'Shrimp']);
64	Profile.set('luckyNumbers', [13, 7]);
65	Profile.set('lastLoginLocation', new Parse.GeoPoint(-27.104919974838154, -52.61428045237739));
66	await Profile.save();
67	
68	console.log('Success!');
1	// Add Profile objects and create table
2	// Adam Sandler
3	let Profile = new Parse.Object('Profile');
4	Profile.set('name', 'Adam Sandler');
5	Profile.set('birthDay', new Date('09/09/1966'));
6	Profile.set('friendCount', 2);
7	Profile.set('favoriteFoods', ['Lobster', 'Bread']);
8	Profile.set('luckyNumbers', [2, 7]);
9	Profile.set('lastLoginLocation', new Parse.GeoPoint(37.38412167489413, -122.01268034622319));
10	await Profile.save();
11	
12	// Britney Spears
13	Profile = new Parse.Object('Profile');
14	Profile.set('name', 'Britney Spears');
15	Profile.set('birthDay', new Date('12/02/1981'));
16	Profile.set('friendCount', 52);
17	Profile.set('favoriteFoods', ['Cake', 'Bread']);
18	Profile.set('luckyNumbers', [22, 7]);
19	Profile.set('lastLoginLocation', new Parse.GeoPoint(37.38412167489413, -122.01268034622319));
20	await Profile.save();
21	
22	// Carson Kressley
23	Profile = new Parse.Object('Profile');
24	Profile.set('name', 'Carson Kressley');
25	Profile.set('birthDay', new Date('11/11/1969'));
26	Profile.set('friendCount', 12);
27	Profile.set('favoriteFoods', ['Fish', 'Cookies']);
28	Profile.set('luckyNumbers', [8, 2]);
29	Profile.set('lastLoginLocation', new Parse.GeoPoint(37.38412167489413, -122.01268034622319));
30	await Profile.save();
31	
32	// Dan Aykroyd
33	// Creates related object Membership for this user only
34	let Membership = new Parse.Object('Membership');
35	Membership.set('name', 'Premium');
36	Membership.set('expirationDate', new Date('10/10/2030'))
37	await Membership.save();
38	Profile = new Parse.Object('Profile');
39	Profile.set('name', 'Dan Aykroyd');
40	Profile.set('birthDay', new Date('07/01/1952'));
41	Profile.set('friendCount', 66);
42	Profile.set('favoriteFoods', ['Jam', 'Peanut Butter']);
43	Profile.set('luckyNumbers', [22, 77]);
44	Profile.set('lastLoginLocation', new Parse.GeoPoint(37.38412167489413, -122.01268034622319));
45	Profile.set('premiumMembership', Membership);
46	await Profile.save();
47	
48	// Eddie Murphy
49	Profile = new Parse.Object('Profile');
50	Profile.set('name', 'Eddie Murphy');
51	Profile.set('birthDay', new Date('04/03/1961'));
52	Profile.set('friendCount', 49);
53	Profile.set('favoriteFoods', ['Lettuce', 'Pepper']);
54	Profile.set('luckyNumbers', [6, 5]);
55	Profile.set('lastLoginLocation', new Parse.GeoPoint(-27.104919974838154, -52.61428045237739));
56	await Profile.save();
57	
58	// Fergie
59	Profile = new Parse.Object('Profile');
60	Profile.set('name', 'Fergie');
61	Profile.set('birthDay', new Date('03/27/1975'));
62	Profile.set('friendCount', 55);
63	Profile.set('favoriteFoods', ['Lobster', 'Shrimp']);
64	Profile.set('luckyNumbers', [13, 7]);
65	Profile.set('lastLoginLocation', new Parse.GeoPoint(-27.104919974838154, -52.61428045237739));
66	await Profile.save();
67	
68	console.log('Success!');
﻿
运行此代码后，您现在应该在数据库中拥有一个 Profile 类，并创建了六个对象。您的新类应如下所示:
﻿
现在让我们来看一下每个 Parse.Query 方法的示例，并简要解释它们的功能。请注意，此列表中的某些方法可以将 options 作为附加参数，但在大多数情况下，它仅与 masterKey 的使用相关，与本指南内容无关，因此在不相关的情况下将省略此可能性。
查询检索器
这些方法负责运行查询并检索其结果，始终存在于您的查询实现中。
cancel
count
distinct
find
findAll
first
get
//Cancels the current network request.
1	let query = new Parse.Query('Profile');
2	let queryResult = await query.find();
3	// This is hard to test in small databases, since by the time
4	// "cancel" is called, the "find" request is already resolved
5	queryResult = query.cancel();
6	console.log(queryResult);
//Cancels the current network request.
1	let query = new Parse.Query('Profile');
2	let queryResult = await query.find();
3	// This is hard to test in small databases, since by the time
4	// "cancel" is called, the "find" request is already resolved
5	queryResult = query.cancel();
6	console.log(queryResult);
﻿
查询条件
这些方法使您能够对查询应用条件约束，这可以说是查询中最重要的操作。请记住，这些操作都可以在检索结果之前进行链式调用，因此可以实现许多组合来满足您的查询需求。
_addCondition
_regexStartWith
containedBy
containedIn
//  Helper that is called by Parse for filtering objects using conditional constants, such as “$gt”, “$eq” and so on. Only usable by users in very specific cases.
1	let query = new Parse.Query('Profile');
2	query._addCondition('friendCount', '$gt', 25);
3	let queryResult = await query.find();
4	console.log(queryResult);
//  Helper that is called by Parse for filtering objects using conditional constants, such as “$gt”, “$eq” and so on. Only usable by users in very specific cases.
1	let query = new Parse.Query('Profile');
2	query._addCondition('friendCount', '$gt', 25);
3	let queryResult = await query.find();
4	console.log(queryResult);
﻿
contains
containsAll
containsAllStartingWith
doesNotExist
//Filters objects in which a string key value contains the provided text value. Be aware that this condition is case-sensitive.
1	let query = new Parse.Query('Profile');
2	// This can be slow in large databases and are case sensitive
3	query.contains('name', 'da');
4	let queryResult = await query.find();
5	console.log(queryResult);
//Filters objects in which a string key value contains the provided text value. Be aware that this condition is case-sensitive.
1	let query = new Parse.Query('Profile');
2	// This can be slow in large databases and are case sensitive
3	query.contains('name', 'da');
4	let queryResult = await query.find();
5	console.log(queryResult);
﻿
doesNotMatchKeyInQuery
doesNotMatchQuery
endsWith
equalTo
//  Requires that a key’s value does not match a value in an object returned by a different Parse.Query. Useful for multi-object querying.
1	let query = new Parse.Query('Profile');
2	// Multiple queries can be combined using this, useful when there are more objects
3	// related, not our example case
4	query.doesNotMatchKeyInQuery('friendCount', 'friendCount', new Parse.Query('Profile').lessThan('friendCount', 50));
5	query.greaterThan('friendCount', 10);
6	let queryResult = await query.find();
7	console.log(queryResult);
//  Requires that a key’s value does not match a value in an object returned by a different Parse.Query. Useful for multi-object querying.
1	let query = new Parse.Query('Profile');
2	// Multiple queries can be combined using this, useful when there are more objects
3	// related, not our example case
4	query.doesNotMatchKeyInQuery('friendCount', 'friendCount', new Parse.Query('Profile').lessThan('friendCount', 50));
5	query.greaterThan('friendCount', 10);
6	let queryResult = await query.find();
7	console.log(queryResult);
﻿
exists
fullText
greaterThan
greaterThanOrEqualTo
//Filters objects in which a key value is set.
1	let query = new Parse.Query('Profile');
2	query.exists('premiumMembership');
3	let queryResult = await query.find();
4	console.log(queryResult);
//Filters objects in which a key value is set.
1	let query = new Parse.Query('Profile');
2	query.exists('premiumMembership');
3	let queryResult = await query.find();
4	console.log(queryResult);
﻿
lessThan
lessThanOrEqualTo
matches
matchesKeyInQuery
//  Filters objects in which a specific key’s value is lesser than the provided value.
1	let query = new Parse.Query('Profile');
2	// lessThan can be used on numbers and dates
3	query.lessThan('birthDay', new Date('08/19/1980'));
4	let queryResult = await query.find();
5	console.log(queryResult);
//  Filters objects in which a specific key’s value is lesser than the provided value.
1	let query = new Parse.Query('Profile');
2	// lessThan can be used on numbers and dates
3	query.lessThan('birthDay', new Date('08/19/1980'));
4	let queryResult = await query.find();
5	console.log(queryResult);
﻿
matchesQuery
notEqualTo
startsWith
//Requires that an object contained in the given key matches another query. Useful for multi-object querying.
1	let innerQuery = new Parse.Query('Membership');
2	innerQuery.greaterThan('expirationDate', new Date());
3	let query = new Parse.Query('Profile');
4	query.exists('premiumMembership');
5	query.matchesQuery('premiumMembership', innerQuery);
6	let queryResult = await query.find();
7	console.log(queryResult);
//Requires that an object contained in the given key matches another query. Useful for multi-object querying.
1	let innerQuery = new Parse.Query('Membership');
2	innerQuery.greaterThan('expirationDate', new Date());
3	let query = new Parse.Query('Profile');
4	query.exists('premiumMembership');
5	query.matchesQuery('premiumMembership', innerQuery);
6	let queryResult = await query.find();
7	console.log(queryResult);
﻿
查询排序
在大多数查询中至关重要，排序可以在 Parse 中轻松实现，甚至可以在两个或多个排序约束之间链接。
addAscending
addDescending
ascending
descending
sortByTextScore
//Sorts by text score when using Parse.Query.fullText
1	let query = new Parse.Query('Profile');
2	query.fullText('name', 'Dan', { diacriticSensitive: false, caseSensitive: false });
3	query.sortByTextScore();
4	let queryResult = await query.find();
5	console.log(queryResult);
//Sorts by text score when using Parse.Query.fullText
1	let query = new Parse.Query('Profile');
2	query.fullText('name', 'Dan', { diacriticSensitive: false, caseSensitive: false });
3	query.sortByTextScore();
4	let queryResult = await query.find();
5	console.log(queryResult);
﻿
字段选择
这些方法影响查询结果中可以包含哪些字段值。
exclude
include
includeAll
select
//  Return all fields in the returned objects except the ones specified.
1	let query = new Parse.Query('Profile');
2	query.exclude('name');
3	let queryResult = await query.find();
4	console.log(queryResult[0].get('name') === undefined);
5	console.log(queryResult[0].get('birthDay'));
//  Return all fields in the returned objects except the ones specified.
1	let query = new Parse.Query('Profile');
2	query.exclude('name');
3	let queryResult = await query.find();
4	console.log(queryResult[0].get('name') === undefined);
5	console.log(queryResult[0].get('birthDay'));
﻿
地理点查询
这些是特定于地理点查询的方法。
near
polygonContains
withinGeoBox
withinKilometers
//  Order objects by how near the key value is from the given GeoPoint.
1	let query = new Parse.Query('Profile');
2	query.near('lastLoginLocation', new Parse.GeoPoint(37.38412167489413, -122.01268034622319));
3	let queryResult = await query.find();
4	console.log(queryResult);
//  Order objects by how near the key value is from the given GeoPoint.
1	let query = new Parse.Query('Profile');
2	query.near('lastLoginLocation', new Parse.GeoPoint(37.38412167489413, -122.01268034622319));
3	let queryResult = await query.find();
4	console.log(queryResult);
﻿
withinMiles
withinPolygon
withinRadians
//Find objects whose key value is near the given GeoPoint and within the maxDistance value. The sorted boolean value determines if the results should be sorted by distance ascending.
1	let query = new Parse.Query('Profile');
2	query.withinMiles('lastLoginLocation', new Parse.GeoPoint(37.38412167489413, -122.01268034622319), 60, true);
3	let queryResult = await query.find();
4	console.log(queryResult);
//Find objects whose key value is near the given GeoPoint and within the maxDistance value. The sorted boolean value determines if the results should be sorted by distance ascending.
1	let query = new Parse.Query('Profile');
2	query.withinMiles('lastLoginLocation', new Parse.GeoPoint(37.38412167489413, -122.01268034622319), 60, true);
3	let queryResult = await query.find();
4	console.log(queryResult);
﻿
分页
这些方法与分页工具相关，适用于将检索大量结果的查询。
limit
skip
withCount
//Sets a flag that will wrap or not the query response in an object containing results, holding the array of Parse.Object and count integer holding the total number of results.
1	let query = new Parse.Query('Profile');
2	query.withCount(true);
3	let queryResult = await query.find();
4	console.log(queryResult);
//Sets a flag that will wrap or not the query response in an object containing results, holding the array of Parse.Object and count integer holding the total number of results.
1	let query = new Parse.Query('Profile');
2	query.withCount(true);
3	let queryResult = await query.find();
4	console.log(queryResult);
﻿
响应处理
这些方法是处理查询响应的助手，使得可以排队回调，这些回调将在查询解决后被调用。它们也充当查询解析器，像是 查找 和 第一个.
each
eachBatch
filter
map
reduce
//  Iterates over each result from the query and calls a callback for each one, in an unspecified order. Note that execution will halt on a rejected promise, so make sure to handle this case if using promises.
1	let query = new Parse.Query('Profile');
2	let queryResult = await query.each((result) => console.log(result));
3	console.log(queryResult);
//  Iterates over each result from the query and calls a callback for each one, in an unspecified order. Note that execution will halt on a rejected promise, so make sure to handle this case if using promises.
1	let query = new Parse.Query('Profile');
2	let queryResult = await query.each((result) => console.log(result));
3	console.log(queryResult);
﻿
复合查询
这些方法将创建复合查询，可以结合多个 Parse.Query 实例以实现更复杂的结果。
_andQuery
_norQuery
_orQuery
and
nor
or
//Compose a compound query that is the OR of the passed queries.
1	let query1 = new Parse.Query('Profile');
2	query1.greaterThan('friendCount', 10);
3	let query2 = new Parse.Query('Profile');
4	query1.lessThan('friendCount', 50);
5	let query = Parse.Query.or(query1, query2);
6	let queryResult = await query.find();
7	console.log(queryResult);
//Compose a compound query that is the OR of the passed queries.
1	let query1 = new Parse.Query('Profile');
2	query1.greaterThan('friendCount', 10);
3	let query2 = new Parse.Query('Profile');
4	query1.lessThan('friendCount', 50);
5	let query = Parse.Query.or(query1, query2);
6	let queryResult = await query.find();
7	console.log(queryResult);
﻿
数据库相关
这些方法与数据库的偏好和操作有关。
aggregate
explain
readPreference
//SWhen using a MongoDB replica set, use this method to choose from which replica the objects will be retrieved. The possible values are PRIMARY (default), PRIMARY_PREFERRED, SECONDARY, SECONDARY_PREFERRED, or NEAREST.
1	let query = new Parse.Query('Profile');
2	query.readPreference(''PRIMARY'');
3	let queryResult = await query.find();
4	console.log(queryResult);
//SWhen using a MongoDB replica set, use this method to choose from which replica the objects will be retrieved. The possible values are PRIMARY (default), PRIMARY_PREFERRED, SECONDARY, SECONDARY_PREFERRED, or NEAREST.
1	let query = new Parse.Query('Profile');
2	query.readPreference(''PRIMARY'');
3	let queryResult = await query.find();
4	console.log(queryResult);
﻿
本地数据存储
这些方法使您能够选择查询的来源并使用本地数据存储.
fromLocalDatastore
fromNetwork
fromPin
fromPinWithName
//Changes the source of this query to a specific group of pinned objects.
1	let query = new Parse.Query('Profile');
2	query.fromPinWithName('pinnedObjects');
3	let queryResult = await query.find();
4	console.log(queryResult);
//Changes the source of this query to a specific group of pinned objects.
1	let query = new Parse.Query('Profile');
2	query.fromPinWithName('pinnedObjects');
3	let queryResult = await query.find();
4	console.log(queryResult);
﻿
JSON 细节
允许将查询表示为 JSON 并检索的方法.
toJSON
withJSON
//Add a previously generated JSON representation of query operations to this query.
1	let query = new Parse.Query('Profile');
2	query.greaterThan('friendCount', 10);
3	let queryJSON = await query.toJSON();
4	let query2 = new Parse.Query('Profile');
5	query2.withJSON(queryJSON);
6	let queryResult = await query2.find();
7	console.log(queryResult);

//Static method to restore Parse.Query by JSON representation, internally calling Parse.Query.withJSON.
1	let query = new Parse.Query('Profile');
2	query.greaterThan('friendCount', 10);
3	let queryJSON = await query.toJSON();
4	let query2 = Parse.Query.withJSON('Profile', queryJSON);
5	let queryResult = await query2.find();
6	console.log(queryResult);
//Add a previously generated JSON representation of query operations to this query.
1	let query = new Parse.Query('Profile');
2	query.greaterThan('friendCount', 10);
3	let queryJSON = await query.toJSON();
4	let query2 = new Parse.Query('Profile');
5	query2.withJSON(queryJSON);
6	let queryResult = await query2.find();
7	console.log(queryResult);

//Static method to restore Parse.Query by JSON representation, internally calling Parse.Query.withJSON.
1	let query = new Parse.Query('Profile');
2	query.greaterThan('friendCount', 10);
3	let queryJSON = await query.toJSON();
4	let query2 = Parse.Query.withJSON('Profile', queryJSON);
5	let queryResult = await query2.find();
6	console.log(queryResult);
﻿
结论
在本指南的最后，您学习了如何在 Parse 中执行每种数据查询方法。在下一个指南中，您将学习在 React Native 中进行复杂的 Parse 查询.
更新日期 27 Jan 2025
此页面是否对您有帮助？
上一个
React Native中使用Parse进行基本数据查询指南
下一个
在 React Native 中使用 Parse 进行关系查询的技术实现