--- title: Flutter应用中使用Parse优化查询性能的技术指南 slug: docs-ch/flutter/parse-sdk/data-objects/flutter-query-cookbook description: 了解如何在Flutter中使用Parse QueryBuilder实现复杂数据查询，提高应用的查询性能和灵活性。 image: https://www.back4app.com/images/logo-social.png createdAt: 2024-03-18T11:26:18.255Z --- # 在Flutter中解析查询食谱 ## 介绍 我们已经看到如何使用 `QueryBuilder` 和 `get` 从Back4App检索单个 `ParseObject`。还有许多其他方法可以使用 `QueryBuilder` 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 `QueryBuilder` 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来使用Flutter在Back4App上执行查询。 ## 前提条件 :::hint{type="info"} - [Android Studio ](https://developer.android.com/studio)或 [安装 VS Code](https://code.visualstudio.com/) (带有 [插件](https://docs.flutter.dev/get-started/editor) Dart 和 Flutter) - 一个在 Back4App 上 [创建的应用](https://www.back4app.com/docs/get-started/new-parse-app): - **注意: **请遵循 [新 Parse 应用教程](https://www.back4app.com/docs/get-started/new-parse-app) 以了解如何在 Back4App 上创建 Parse 应用。 - 一个连接到 Back4app 的 Flutter 应用。 - **注意: **请遵循 [在 Flutter 项目中安装 Parse SDK](https://www.back4app.com/docs/flutter/parse-sdk/parse-flutter-sdk) 以创建一个连接到 Back4App 的 Flutter 项目。 - 一台运行 Android 或 iOS 的设备（或虚拟设备）。 ::: ## 目标 探索 `QueryBuilder` 类的不同方法。 ## QueryBuilder 类 任何 Parse 查询操作都使用 `QueryBuilder` 对象类型，这将帮助您在整个应用程序中从数据库中检索特定数据。 要创建一个新的 `QueryBuilder`，您需要将所需的 `ParseObject` 子类作为参数传递，这将包含您的查询结果。 重要的是要知道 `QueryBuilder` 只有在调用检索方法 `query` 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 [这里阅读有关 QueryBuilder 类的更多信息](https://github.com/parse-community/Parse-SDK-Flutter/tree/master/packages/flutter#complex-queries)。 ## 在 Back4App 上使用 JavaScript 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，您可以直接运行 JavaScript 代码。在本指南中，您将使用它在 Back4App 中存储数据对象。在您的应用主仪表板上，转到 `Core->API Console->Javascript`. ![](https://api.archbee.com/api/optimize/yD3zCY-NNBBIfd0uqcfR5/3TcRJJck5LuleYZ4hQI4Y_image.png) ## 保存您的数据对象 要在本指南中运行查询，您首先需要用一些数据填充您的应用。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，使用名人的名字和以下字段: - 字符串类型 `名称`: - 日期类型 `生日`: - 数字（整数）类型 `好友数量`: - 数组（字符串列表）类型 `最爱食物`: - 数组（数字列表）类型 `幸运数字`: - 地理点类型 `最后登录位置`: 这是 `Parse.Object` 类的创建代码，所以请在您的 API 控制台中运行它: ```dart 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 39 Profile = new Parse.Object('Profile'); 40 Profile.set('name', 'Dan Aykroyd'); 41 Profile.set('birthDay', new Date('07/01/1952')); 42 Profile.set('friendCount', 66); 43 Profile.set('favoriteFoods', ['Jam', 'Peanut Butter']); 44 Profile.set('luckyNumbers', [22, 77]); 45 Profile.set('lastLoginLocation', new Parse.GeoPoint(37.38412167489413, -122.01268034622319)); 46 Profile.set('premiumMembership', Membership); 47 await Profile.save(); 48 49 // Eddie Murphy 50 Profile = new Parse.Object('Profile'); 51 Profile.set('name', 'Eddie Murphy'); 52 Profile.set('birthDay', new Date('04/03/1961')); 53 Profile.set('friendCount', 49); 54 Profile.set('favoriteFoods', ['Lettuce', 'Pepper']); 55 Profile.set('luckyNumbers', [6, 5]); 56 Profile.set('lastLoginLocation', new Parse.GeoPoint(-27.104919974838154, -52.61428045237739)); 57 await Profile.save(); 58 59 // Fergie 60 Profile = new Parse.Object('Profile'); 61 Profile.set('name', 'Fergie'); 62 Profile.set('birthDay', new Date('03/27/1975')); 63 Profile.set('friendCount', 55); 64 Profile.set('favoriteFoods', ['Lobster', 'Shrimp']); 65 Profile.set('luckyNumbers', [13, 7]); 66 Profile.set('lastLoginLocation', new Parse.GeoPoint(-27.104919974838154, -52.61428045237739)); 67 await Profile.save(); 68 69 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: ![](https://api.archbee.com/api/optimize/yD3zCY-NNBBIfd0uqcfR5/K59IBJVFpp-kIDPI2S5ho_image.png) 现在让我们来看一下每个 `QueryBuilder` 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。 :::CodeblockTabs count ```javascript //Retrieves the count of ParseObject results that meet the query criteria. 1 QueryBuilder queryBuilder = QueryBuilder(ParseObject('Profile')); 2 var apiResponse = await queryPlayers.count(); 3 if (apiResponse.success && apiResponse.result != null) { 4 int countGames = apiResponse.count; 5 } ``` getObject ```javascript //This quick method is used to retrieve a single ParseObject instance when you know its objectId. 1 ///To retrieve one object of a Class it is not necessary to create a ParseQuery. 2 ///We can query using ParseObject 3 final apiResponse = await ParseObject('Profile').getObject('C6ENdLnFdQ'); 4 5 if (apiResponse.success && apiResponse.results != null) { 6 for (var o in apiResponse.results) { 7 final object = o as ParseObject; 8 print('${object.objectId} - ${object.get('name')}'); 9 } 10 } ``` getAll ```javascript //Retrieves a complete list of ParseObjects. 1 ///To retrieve all objects of a Class it is not necessary to create a ParseQuery. 2 ///We can query using ParseObject 3 final apiResponse = await ParseObject('Profile').getAll(); 4 5 if (apiResponse.success && apiResponse.results != null) { 6 for (var o in apiResponse.results) { 7 final object = o as ParseObject; 8 print('${object.objectId} - ${object.get('name')}'); 9 } 10 } ``` query ```javascript //This is the basic method for retrieving your query results, always returning an list of ParseObject instances, being empty when none are found. 1 final QueryBuilder parseQuery = QueryBuilder(ParseObject('Profile')); 2 // When using .query() in a query without other operations, you will 3 // get every object saved in your class 4 final apiResponse = await parseQuery.query(); 5 6 if (apiResponse.success && apiResponse.results != null) { 7 for (var o in apiResponse.results) { 8 final object = o as ParseObject; 9 print('${object.objectId} - ${object.get('name')}'); 10 } 11 } ``` ::: ## 查询条件 这些方法使您能够对查询应用条件约束，这可以说是查询中最重要的操作。 请记住，这些操作都可以在检索结果之前链接，因此可以实现许多组合来满足您的查询需求。 :::CodeblockTabs whereDoesNotMatchKeyInQuery ```dart //Requires that a key’s value does not match a value in an object returned by a different Parse.Query. Useful for multi-object querying. 1 final QueryBuilder parseQuery = QueryBuilder(ParseObject('Profile')); 2 parseQuery.whereDoesNotMatchKeyInQuery( 3 'friendCount', 4 'friendCount', 5 QueryBuilder(ParseObject('Profile')) 6 ..whereLessThan('friendCount', 50)); 7 parseQuery.whereGreaterThan('friendCount', 10); 8 final apiResponse = await parseQuery.query(); 9 10 if (apiResponse.success && apiResponse.results != null) { 11 for (var object in apiResponse.results as List) { 12 print('${object.objectId} - Name: ${object.get('name')} - friendCount: ${object.get('friendCount')}'); 13 } 14 } ``` whereArrayContainsAll ```dart //Filters objects in which an array type key value must contain every value provided. 1 final QueryBuilder parseQuery = QueryBuilder(ParseObject('Profile')); 2 parseQuery.whereArrayContainsAll('luckyNumbers', [2, 7]); 3 final apiResponse = await parseQuery.query(); 4 5 if (apiResponse.success && apiResponse.results != null) { 6 for (var object in apiResponse.results as List) { 7 print('${object.objectId} - ${object.get('name')}'); 8 } 9 } ``` whereCoitainedIn ```dart //Filters objects in which a key value is contained in the provided array of values. 1 final QueryBuilder parseQuery = QueryBuilder(ParseObject('Profile')); 2 parseQuery.whereContainedIn('luckyNumbers', [2, 7]); 3 final apiResponse = await parseQuery.query(); 4 5 if (apiResponse.success && apiResponse.results != null) { 6 for (var object in apiResponse.results as List) { 7 print('${object.objectId} - ${object.get('name')}'); 8 } 9 } ``` ::: :::CodeblockTabs whereContains ```dart //Filters objects in which a string key value contains the provided text value. Be aware that this condition is case-sensitive. 1 final QueryBuilder parseQuery = QueryBuilder(ParseObject('Profile')); 2 // This can be slow in large databases 3 parseQuery.whereContains('name', 'an'); 4 final apiResponse = await parseQuery.query(); 5 6 if (apiResponse.success && apiResponse.results != null) { 7 for (var object in apiResponse.results as List) { 8 print('${object.objectId} - ${object.get('name')}'); 9 } 10 } ``` whereDoesNotMatchQuery ```dart //Requires that an object contained in the given key does not match another query. Useful for multi-object querying. 1 final QueryBuilder innerQuery = QueryBuilder(ParseObject('Membership')); 2 innerQuery.whereGreaterThan('expirationDate', DateTime.now()); 3 4 final QueryBuilder parseQuery = QueryBuilder(ParseObject('Profile')); 5 6 parseQuery.whereDoesNotMatchQuery('premiumMembership', innerQuery); 7 8 final apiResponse = await parseQuery.query(); 9 10 if (apiResponse.success && apiResponse.results != null) { 11 for (var object in apiResponse.results as List) { 12 print('${object.objectId} - Name: ${object.get('name')}'); 13 } 14 } ``` whereEndsWith ```dart //Filters objects where specific key’s value ends with value. 1 final QueryBuilder parseQuery = QueryBuilder(ParseObject('Profile')); 2 3 parseQuery.whereEndsWith('name', 'ie'); 4 final apiResponse = await parseQuery.query(); 5 6 if (apiResponse.success && apiResponse.results != null) { 7 for (var o in apiResponse.results) { 8 final object = o as ParseObject; 9 print('${object.objectId} - ${object.get('name')}'); 10 } 11 } ``` ::: :::CodeblockTabs whereEqualTo ```dart //Filters objects in which a specific key’s value is equal to the provided value. 1 final QueryBuilder parseQuery = QueryBuilder(ParseObject('Profile')); 2 3 parseQuery.whereEqualTo('friendCount', 2); 4 final apiResponse = await parseQuery.query(); 5 6 if (apiResponse.success && apiResponse.results != null) { 7 for (var o in apiResponse.results) { 8 final object = o as ParseObject; 9 print('${object.objectId} - ${object.get('name')}'); 10 } 11 } ``` whereGreaterThan ```dart //Filters objects in which a specific key’s value is greater than the provided value. 1 final QueryBuilder parseQuery = QueryBuilder(ParseObject('Profile')); 2 3 parseQuery.whereGreaterThan('birthDay', DateTime(1980, 08, 19)); 4 final apiResponse = await parseQuery.query(); 5 6 if (apiResponse.success && apiResponse.results != null) { 7 for (var object in apiResponse.results as List) { 8 print('${object.objectId} - ${object.get('name')}'); 9 } 10 } ``` whereGreaterThanOrEqualsTo ```dart //Filters objects in which a specific key’s value is greater than or equal to the provided value. 1 final QueryBuilder parseQuery = QueryBuilder(ParseObject('Profile')); 2 3 parseQuery.whereGreaterThanOrEqualsTo('friendCount', 49); 4 final apiResponse = await parseQuery.query(); 5 6 if (apiResponse.success && apiResponse.results != null) { 7 for (var object in apiResponse.results as List) { 8 print('${object.objectId} - ${object.get('name')}'); 9 } 10 } ``` ::: :::CodeblockTabs whereLessThan ```dart //Filters objects in which a specific key’s value is lesser than the provided value. 1 final QueryBuilder parseQuery = QueryBuilder(ParseObject('Profile')); 2 3 parseQuery.whereLessThan('birthDay', DateTime(1980, 08, 19)); 4 final apiResponse = await parseQuery.query(); 5 6 if (apiResponse.success && apiResponse.results != null) { 7 for (var object in apiResponse.results as List) { 8 print('${object.objectId} - ${object.get('name')}'); 9 } 10 } ``` whereLessThanOrEqualTo ```dart //Filters objects in which a specific key’s value is lesser than or equal to the provided value. 1 final QueryBuilder parseQuery = QueryBuilder(ParseObject('Profile')); 2 3 parseQuery.whereLessThanOrEqualTo('friendCount', 49); 4 final apiResponse = await parseQuery.query(); 5 6 if (apiResponse.success && apiResponse.results != null) { 7 for (var object in apiResponse.results as List) { 8 print('${object.objectId} - ${object.get('name')}'); 9 } 10 } ``` whereMatchesKeyInQuery ```dart //Requires that a key’s value matches a value in an object returned by a different Parse.Query. Useful for multi-object querying. 1 final QueryBuilder parseQuery = QueryBuilder(ParseObject('Profile')); 2 parseQuery.whereMatchesKeyInQuery( 3 'friendCount', 4 'friendCount', 5 QueryBuilder(ParseObject('Profile')) 6 ..whereLessThan('friendCount', 50)); 7 8 final apiResponse = await parseQuery.query(); 9 10 if (apiResponse.success && apiResponse.results != null) { 11 for (var object in apiResponse.results as List) { 12 print('${object.objectId} - Name: ${object.get('name')} - friendCount: ${object.get('friendCount')}'); 13 } 14 } ``` ::: :::CodeblockTabs whereMatchesQuery ```dart //Requires that an object contained in the given key matches another query. Useful for multi-object querying. 1 final QueryBuilder innerQuery = QueryBuilder(ParseObject('Membership')); 2 innerQuery.whereGreaterThan('expirationDate', DateTime.now()); 3 4 final QueryBuilder parseQuery = QueryBuilder(ParseObject('Profile')); 5 6 parseQuery.whereValueExists('premiumMembership', true); 7 parseQuery.whereMatchesQuery('premiumMembership', innerQuery); 8 9 final apiResponse = await parseQuery.query(); 10 11 if (apiResponse.success && apiResponse.results != null) { 12 for (var object in apiResponse.results as List) { 13 print('${object.objectId} - Name: ${object.get('name')}'); 14 } 15 } ``` whereNotContainedIn ```dart //Filters objects in which a key value is not contained in the provided array of values. 1 final QueryBuilder parseQuery = QueryBuilder(ParseObject('Profile')); 2 parseQuery.whereNotContainedIn('luckyNumbers', [2, 7]); 3 final apiResponse = await parseQuery.query(); 4 5 if (apiResponse.success && apiResponse.results != null) { 6 for (var object in apiResponse.results as List) { 7 print('${object.objectId} - ${object.get('name')}'); 8 } 9 } ``` whereNotEqualTo ```dart //Filters objects in which a specific key’s value is not equal to the provided value. 1 final QueryBuilder parseQuery = QueryBuilder(ParseObject('Profile')); 2 3 parseQuery.whereNotEqualTo('friendCount', 2); 4 final apiResponse = await parseQuery.query(); 5 6 if (apiResponse.success && apiResponse.results != null) { 7 for (var object in apiResponse.results as List) { 8 print('${object.objectId} - ${object.get('name')}'); 9 } 10 } ``` whereStartsWith ```dart //Filters objects where specific key’s value starts with value. 1 final QueryBuilder parseQuery = QueryBuilder(ParseObject('Profile')); 2 3 parseQuery.whereStartsWith('name', 'Adam'); 4 final apiResponse = await parseQuery.query(); 5 6 if (apiResponse.success && apiResponse.results != null) { 7 for (var o in apiResponse.results) { 8 final object = o as ParseObject; 9 print('${object.objectId} - ${object.get('name')}'); 10 } 11 } ``` whereValueExists ```dart //Filters objects in which a key value is set or no. 1 final QueryBuilder parseQuery = QueryBuilder(ParseObject('Profile')); 2 //true - retrieve documents with field set 3 //false - retrieve documents without field set 4 parseQuery.whereValueExists('premiumMembership', true); 5 final apiResponse = await parseQuery.query(); 6 7 if (apiResponse.success && apiResponse.results != null) { 8 for (var object in apiResponse.results as List) { 9 print('${object.objectId} - ${object.get('name')}'); 10 } 11 } ``` ::: ## 查询排序 在大多数查询中至关重要，排序可以在Parse中轻松实现，甚至可以在两个或多个排序约束之间链接。 :::CodeblockTabs orderByAscending ```dart //Sort the results in ascending order, this can be chained without overwriting previous orderings. Multiple keys can be used to solve ordering ties. 1 final QueryBuilder parseQuery = QueryBuilder(ParseObject('Profile')); 2 parseQuery.orderByAscending('name'); 3 final apiResponse = await parseQuery.query(); 4 5 if (apiResponse.success && apiResponse.results != null) { 6 for (var object in apiResponse.results as List) { 7 print('${object.objectId} - ${object.get('name')}'); 8 } 9 } ``` orderByDescending ```dart //Sort the results in descending order, this can be chained without overwriting previous orderings. Multiple keys can be used to solve ordering ties. 1 final QueryBuilder parseQuery = QueryBuilder(ParseObject('Profile')); 2 parseQuery.orderByDescending('name'); 3 final apiResponse = await parseQuery.query(); 4 5 if (apiResponse.success && apiResponse.results != null) { 6 for (var object in apiResponse.results as List) { 7 print('${object.objectId} - ${object.get('name')}'); 8 } 9 } ``` ::: ## 字段选择 这些方法影响查询结果中可以包含哪些字段值。 :::CodeblockTabs excludeKeys ```dart //Return all fields in the returned objects except the ones specified. 1 final QueryBuilder parseQuery = QueryBuilder(ParseObject('Profile')); 2 parseQuery.excludeKeys(['name']); 3 final apiResponse = await parseQuery.query(); 4 5 if (apiResponse.success && apiResponse.results != null) { 6 for (var object in apiResponse.results as List) { 7 //Name = null 8 print('${object.objectId} - Name: ${object.get('name')} - Birthday: ${object.get('birthDay')}'); 9 } 10 } ``` includeObject ```dart //Includes nested ParseObjects for the provided key. 1 final QueryBuilder parseQuery = QueryBuilder(ParseObject('Profile')); 2 parseQuery.includeObject(['premiumMembership']); 3 final apiResponse = await parseQuery.query(); 4 5 if (apiResponse.success && apiResponse.results != null) { 6 for (var object in apiResponse.results as List) { 7 //Name = null 8 print('${object.objectId} - Name: ${object.get('name')} - premiumMembership: ${object.get('premiumMembership').toString()}'); 9 } 10 } ``` keysToReturn ```dart //Return only the specified fields in the returned objects. 1 final QueryBuilder parseQuery = QueryBuilder(ParseObject('Profile')); 2 parseQuery.keysToReturn(['name']); 3 final apiResponse = await parseQuery.query(); 4 5 if (apiResponse.success && apiResponse.results != null) { 6 for (var object in apiResponse.results as List) { 7 //Birthday = null 8 print('${object.objectId} - Name: ${object.get('name')} - Birthday: ${object.get('birthDay')}'); 9 } 10 } ``` ::: ## 地理点查询 这些是特定于GeoPoint查询的方法。 :::CodeblockTabs whereNear ```dart //Return all fields in the returned objects except the ones specified. 1 final QueryBuilder parseQuery = QueryBuilder(ParseObject('Profile')); 2 parseQuery.whereNear( 3 'lastLoginLocation', 4 ParseGeoPoint(latitude: 37.38412167489413, longitude: -122.01268034622319) 5 ); 6 7 final apiResponse = await parseQuery.query(); 8 9 if (apiResponse.success && apiResponse.results != null) { 10 for (var object in apiResponse.results as List) { 11 print('${object.objectId} - Name: ${object.get('name')} - GeoPoint: ${object.get('lastLoginLocation').toJson()}'); 12 } 13 } ``` whereWithinGeoBox ```dart 1 final QueryBuilder parseQuery = QueryBuilder(ParseObject('Profile')); 2 parseQuery.whereWithinGeoBox( 3 'lastLoginLocation', 4 ParseGeoPoint(latitude: 37.38412167489413, longitude: -122.01268034622319), 5 ParseGeoPoint(latitude: 37.28412167489413, longitude: -121.91268034622319) 6 ); 7 8 final apiResponse = await parseQuery.query(); 9 10 if (apiResponse.success && apiResponse.results != null) { 11 for (var object in apiResponse.results as List) { 12 print('${object.objectId} - Name: ${object.get('name')} - GeoPoint: ${object.get('lastLoginLocation').toJson()}'); 13 } 14 } ``` ::: :::CodeblockTabs whereWithinKilometers ```dart 1 final QueryBuilder parseQuery = QueryBuilder(ParseObject('Profile')); 2 parseQuery.whereWithinKilometers( 3 'lastLoginLocation', 4 ParseGeoPoint(latitude: 37.38412167489413, longitude: -122.01268034622319), 5 100 6 ); 7 8 final apiResponse = await parseQuery.query(); 9 10 if (apiResponse.success && apiResponse.results != null) { 11 for (var object in apiResponse.results as List) { 12 print('${object.objectId} - Name: ${object.get('name')} - GeoPoint: ${object.get('lastLoginLocation').toJson()}'); 13 } 14 } ``` whereWithinMiles ```dart 1 final QueryBuilder parseQuery = QueryBuilder(ParseObject('Profile')); 2 parseQuery.whereWithinMiles( 3 'lastLoginLocation', 4 ParseGeoPoint(latitude: 37.38412167489413, longitude: -122.01268034622319), 5 100 6 ); 7 8 final apiResponse = await parseQuery.query(); 9 10 if (apiResponse.success && apiResponse.results != null) { 11 for (var object in apiResponse.results as List) { 12 print('${object.objectId} - Name: ${object.get('name')} - GeoPoint: ${object.get('lastLoginLocation').toJson()}'); 13 } 14 } ``` whereWithinRadians ```dart 1 final QueryBuilder parseQuery = QueryBuilder(ParseObject('Profile')); 2 parseQuery.whereWithinRadians( 3 'lastLoginLocation', 4 ParseGeoPoint(latitude: 37.38412167489413, longitude: -122.01268034622319), 5 100 6 ); 7 8 final apiResponse = await parseQuery.query(); 9 10 if (apiResponse.success && apiResponse.results != null) { 11 for (var object in apiResponse.results as List) { 12 print('${object.objectId} - Name: ${object.get('name')} - GeoPoint: ${object.get('lastLoginLocation').toJson()}'); 13 } 14 } ``` ::: ## 分页 这些方法与分页工具相关，适用于将检索大量结果的查询。 :::CodeblockTabs setAmountToSkip ```dart 1 final QueryBuilder parseQuery = QueryBuilder(ParseObject('Profile')); 2 parseQuery.setAmountToSkip(2); 3 final apiResponse = await parseQuery.query(); 4 5 if (apiResponse.success && apiResponse.results != null) { 6 for (var object in apiResponse.results as List) { 7 print('${object.objectId} - Name: ${object.get('name')}'); 8 } 9 } ``` setLimit ```dart 1 final QueryBuilder parseQuery = QueryBuilder(ParseObject('Profile')); 2 parseQuery.setLimit(2); 3 final apiResponse = await parseQuery.query(); 4 5 if (apiResponse.success && apiResponse.results != null) { 6 for (var object in apiResponse.results as List) { 7 print('${object.objectId} - Name: ${object.get('name')}'); 8 } 9 } ``` ::: ## 复合查询 这些方法将创建复合查询，可以将多个 ParseQuery 实例组合在一起以实现更复杂的结果。 :::CodeblockTabs or ```dart //Compose a compound query that is the OR of the passed queries. 1 final QueryBuilder query1 = QueryBuilder(ParseObject('Profile')); 2 query1.whereGreaterThan('friendCount', 10); 3 4 final QueryBuilder query2 = QueryBuilder(ParseObject('Profile')); 5 query2.whereLessThan('friendCount', 50); 6 7 QueryBuilder mainQuery = QueryBuilder.or( 8 ParseObject("Profile"), 9 [query1, query2], 10 ); 11 12 final apiResponse = await mainQuery.query(); 13 14 if (apiResponse.success && apiResponse.results != null) { 15 for (var object in apiResponse.results as List) { 16 print('${object.objectId} - Name: ${object.get('name')}'); 17 } 18 } ``` ::: ## 结论 在本指南的最后，您学习了如何执行 Parse 中的每种数据查询方法。在下一个指南中，您将学习 Flutter 中复杂的 Parse 查询。