Flutter应用中使用Parse优化查询性能的技术指南

16 分

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 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\ 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 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。 count //retrieves the count of parseobject results that meet the query criteria 1 querybuilder\<parseobject> querybuilder = querybuilder\<parseobject>(parseobject('profile')); 2 var apiresponse = await queryplayers count(); 3 if (apiresponse success && apiresponse result != null) { 4 int countgames = apiresponse count; 5 } getobject //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} ${object get\<string>('name')}'); 9 } 10 } getall //retrieves a complete list of parseobjects 1 ///to retrieve all objects of a class it is not necessary to create a parsequery 2 ///we can query using parseobject 3 final apiresponse = await parseobject('profile') getall(); 4 5 if (apiresponse success && apiresponse results != null) { 6 for (var o in apiresponse results) { 7 final object = o as parseobject; 8 print('${object objectid} ${object get\<string>('name')}'); 9 } 10 } query //this is the basic method for retrieving your query results, always returning an list of parseobject instances, being empty when none are found 1 final querybuilder\<parseobject> parsequery = querybuilder\<parseobject>(parseobject('profile')); 2 // when using query() in a query without other operations, you will 3 // get every object saved in your class 4 final apiresponse = await parsequery query(); 5 6 if (apiresponse success && apiresponse results != null) { 7 for (var o in apiresponse results) { 8 final object = o as parseobject; 9 print('${object objectid} ${object get\<string>('name')}'); 10 } 11 } 查询条件这些方法使您能够对查询应用条件约束，这可以说是查询中最重要的操作。请记住，这些操作都可以在检索结果之前链接，因此可以实现许多组合来满足您的查询需求。 wheredoesnotmatchkeyinquery //requires that a key’s value does not match a value in an object returned by a different parse query useful for multi object querying 1 final querybuilder\<parseobject> parsequery = querybuilder\<parseobject>(parseobject('profile')); 2 parsequery wheredoesnotmatchkeyinquery( 3 'friendcount', 4 'friendcount', 5 querybuilder\<parseobject>(parseobject('profile')) 6 wherelessthan('friendcount', 50)); 7 parsequery wheregreaterthan('friendcount', 10); 8 final apiresponse = await parsequery query(); 9 10 if (apiresponse success && apiresponse results != null) { 11 for (var object in apiresponse results as list\<parseobject>) { 12 print('${object objectid} name ${object get\<string>('name')} friendcount ${object get\<int>('friendcount')}'); 13 } 14 } wherearraycontainsall //filters objects in which an array type key value must contain every value provided 1 final querybuilder\<parseobject> parsequery = querybuilder\<parseobject>(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\<parseobject>) { 7 print('${object objectid} ${object get\<string>('name')}'); 8 } 9 } wherecoitainedin //filters objects in which a key value is contained in the provided array of values 1 final querybuilder\<parseobject> parsequery = querybuilder\<parseobject>(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\<parseobject>) { 7 print('${object objectid} ${object get\<string>('name')}'); 8 } 9 } wherecontains //filters objects in which a string key value contains the provided text value be aware that this condition is case sensitive 1 final querybuilder\<parseobject> parsequery = querybuilder\<parseobject>(parseobject('profile')); 2 // this can be slow in large databases 3 parsequery wherecontains('name', 'an'); 4 final apiresponse = await parsequery query(); 5 6 if (apiresponse success && apiresponse results != null) { 7 for (var object in apiresponse results as list\<parseobject>) { 8 print('${object objectid} ${object get\<string>('name')}'); 9 } 10 } wheredoesnotmatchquery //requires that an object contained in the given key does not match another query useful for multi object querying 1 final querybuilder\<parseobject> innerquery = querybuilder\<parseobject>(parseobject('membership')); 2 innerquery wheregreaterthan('expirationdate', datetime now()); 3 4 final querybuilder\<parseobject> parsequery = querybuilder\<parseobject>(parseobject('profile')); 5 6 parsequery wheredoesnotmatchquery('premiummembership', innerquery); 7 8 final apiresponse = await parsequery query(); 9 10 if (apiresponse success && apiresponse results != null) { 11 for (var object in apiresponse results as list\<parseobject>) { 12 print('${object objectid} name ${object get\<string>('name')}'); 13 } 14 } whereendswith //filters objects where specific key’s value ends with value 1 final querybuilder\<parseobject> parsequery = querybuilder\<parseobject>(parseobject('profile')); 2 3 parsequery whereendswith('name', 'ie'); 4 final apiresponse = await parsequery query(); 5 6 if (apiresponse success && apiresponse results != null) { 7 for (var o in apiresponse results) { 8 final object = o as parseobject; 9 print('${object objectid} ${object get\<string>('name')}'); 10 } 11 } whereequalto //filters objects in which a specific key’s value is equal to the provided value 1 final querybuilder\<parseobject> parsequery = querybuilder\<parseobject>(parseobject('profile')); 2 3 parsequery whereequalto('friendcount', 2); 4 final apiresponse = await parsequery query(); 5 6 if (apiresponse success && apiresponse results != null) { 7 for (var o in apiresponse results) { 8 final object = o as parseobject; 9 print('${object objectid} ${object get\<string>('name')}'); 10 } 11 } wheregreaterthan //filters objects in which a specific key’s value is greater than the provided value 1 final querybuilder\<parseobject> parsequery = querybuilder\<parseobject>(parseobject('profile')); 2 3 parsequery wheregreaterthan('birthday', datetime(1980, 08, 19)); 4 final apiresponse = await parsequery query(); 5 6 if (apiresponse success && apiresponse results != null) { 7 for (var object in apiresponse results as list\<parseobject>) { 8 print('${object objectid} ${object get\<string>('name')}'); 9 } 10 } wheregreaterthanorequalsto //filters objects in which a specific key’s value is greater than or equal to the provided value 1 final querybuilder\<parseobject> parsequery = querybuilder\<parseobject>(parseobject('profile')); 2 3 parsequery wheregreaterthanorequalsto('friendcount', 49); 4 final apiresponse = await parsequery query(); 5 6 if (apiresponse success && apiresponse results != null) { 7 for (var object in apiresponse results as list\<parseobject>) { 8 print('${object objectid} ${object get\<string>('name')}'); 9 } 10 } wherelessthan //filters objects in which a specific key’s value is lesser than the provided value 1 final querybuilder\<parseobject> parsequery = querybuilder\<parseobject>(parseobject('profile')); 2 3 parsequery wherelessthan('birthday', datetime(1980, 08, 19)); 4 final apiresponse = await parsequery query(); 5 6 if (apiresponse success && apiresponse results != null) { 7 for (var object in apiresponse results as list\<parseobject>) { 8 print('${object objectid} ${object get\<string>('name')}'); 9 } 10 } wherelessthanorequalto //filters objects in which a specific key’s value is lesser than or equal to the provided value 1 final querybuilder\<parseobject> parsequery = querybuilder\<parseobject>(parseobject('profile')); 2 3 parsequery wherelessthanorequalto('friendcount', 49); 4 final apiresponse = await parsequery query(); 5 6 if (apiresponse success && apiresponse results != null) { 7 for (var object in apiresponse results as list\<parseobject>) { 8 print('${object objectid} ${object get\<string>('name')}'); 9 } 10 } wherematcheskeyinquery //requires that a key’s value matches a value in an object returned by a different parse query useful for multi object querying 1 final querybuilder\<parseobject> parsequery = querybuilder\<parseobject>(parseobject('profile')); 2 parsequery wherematcheskeyinquery( 3 'friendcount', 4 'friendcount', 5 querybuilder\<parseobject>(parseobject('profile')) 6 wherelessthan('friendcount', 50)); 7 8 final apiresponse = await parsequery query(); 9 10 if (apiresponse success && apiresponse results != null) { 11 for (var object in apiresponse results as list\<parseobject>) { 12 print('${object objectid} name ${object get\<string>('name')} friendcount ${object get\<int>('friendcount')}'); 13 } 14 } wherematchesquery //requires that an object contained in the given key matches another query useful for multi object querying 1 final querybuilder\<parseobject> innerquery = querybuilder\<parseobject>(parseobject('membership')); 2 innerquery wheregreaterthan('expirationdate', datetime now()); 3 4 final querybuilder\<parseobject> parsequery = querybuilder\<parseobject>(parseobject('profile')); 5 6 parsequery wherevalueexists('premiummembership', true); 7 parsequery wherematchesquery('premiummembership', innerquery); 8 9 final apiresponse = await parsequery query(); 10 11 if (apiresponse success && apiresponse results != null) { 12 for (var object in apiresponse results as list\<parseobject>) { 13 print('${object objectid} name ${object get\<string>('name')}'); 14 } 15 } wherenotcontainedin //filters objects in which a key value is not contained in the provided array of values 1 final querybuilder\<parseobject> parsequery = querybuilder\<parseobject>(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\<parseobject>) { 7 print('${object objectid} ${object get\<string>('name')}'); 8 } 9 } wherenotequalto //filters objects in which a specific key’s value is not equal to the provided value 1 final querybuilder\<parseobject> parsequery = querybuilder\<parseobject>(parseobject('profile')); 2 3 parsequery wherenotequalto('friendcount', 2); 4 final apiresponse = await parsequery query(); 5 6 if (apiresponse success && apiresponse results != null) { 7 for (var object in apiresponse results as list\<parseobject>) { 8 print('${object objectid} ${object get\<string>('name')}'); 9 } 10 } wherestartswith //filters objects where specific key’s value starts with value 1 final querybuilder\<parseobject> parsequery = querybuilder\<parseobject>(parseobject('profile')); 2 3 parsequery wherestartswith('name', 'adam'); 4 final apiresponse = await parsequery query(); 5 6 if (apiresponse success && apiresponse results != null) { 7 for (var o in apiresponse results) { 8 final object = o as parseobject; 9 print('${object objectid} ${object get\<string>('name')}'); 10 } 11 } wherevalueexists //filters objects in which a key value is set or no 1 final querybuilder\<parseobject> parsequery = querybuilder\<parseobject>(parseobject('profile')); 2 //true retrieve documents with field set 3 //false retrieve documents without field set 4 parsequery wherevalueexists('premiummembership', true); 5 final apiresponse = await parsequery query(); 6 7 if (apiresponse success && apiresponse results != null) { 8 for (var object in apiresponse results as list\<parseobject>) { 9 print('${object objectid} ${object get\<string>('name')}'); 10 } 11 } 查询排序在大多数查询中至关重要，排序可以在parse中轻松实现，甚至可以在两个或多个排序约束之间链接。 orderbyascending //sort the results in ascending order, this can be chained without overwriting previous orderings multiple keys can be used to solve ordering ties 1 final querybuilder\<parseobject> parsequery = querybuilder\<parseobject>(parseobject('profile')); 2 parsequery orderbyascending('name'); 3 final apiresponse = await parsequery query(); 4 5 if (apiresponse success && apiresponse results != null) { 6 for (var object in apiresponse results as list\<parseobject>) { 7 print('${object objectid} ${object get\<string>('name')}'); 8 } 9 } orderbydescending //sort the results in descending order, this can be chained without overwriting previous orderings multiple keys can be used to solve ordering ties 1 final querybuilder\<parseobject> parsequery = querybuilder\<parseobject>(parseobject('profile')); 2 parsequery orderbydescending('name'); 3 final apiresponse = await parsequery query(); 4 5 if (apiresponse success && apiresponse results != null) { 6 for (var object in apiresponse results as list\<parseobject>) { 7 print('${object objectid} ${object get\<string>('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。 excludekeys //return all fields in the returned objects except the ones specified 1 final querybuilder\<parseobject> parsequery = querybuilder\<parseobject>(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\<parseobject>) { 7 //name = null 8 print('${object objectid} name ${object get\<string>('name')} birthday ${object get\<datetime>('birthday')}'); 9 } 10 } includeobject //includes nested parseobjects for the provided key 1 final querybuilder\<parseobject> parsequery = querybuilder\<parseobject>(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\<parseobject>) { 7 //name = null 8 print('${object objectid} name ${object get\<string>('name')} premiummembership ${object get\<parseobject>('premiummembership') tostring()}'); 9 } 10 } keystoreturn //return only the specified fields in the returned objects 1 final querybuilder\<parseobject> parsequery = querybuilder\<parseobject>(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\<parseobject>) { 7 //birthday = null 8 print('${object objectid} name ${object get\<string>('name')} birthday ${object get\<datetime>('birthday')}'); 9 } 10 } 地理点查询这些是特定于geopoint查询的方法。 wherenear //return all fields in the returned objects except the ones specified 1 final querybuilder\<parseobject> parsequery = querybuilder\<parseobject>(parseobject('profile')); 2 parsequery wherenear( 3 'lastloginlocation', 4 parsegeopoint(latitude 37 38412167489413, longitude 122 01268034622319) 5 ); 6 7 final apiresponse = await parsequery query(); 8 9 if (apiresponse success && apiresponse results != null) { 10 for (var object in apiresponse results as list\<parseobject>) { 11 print('${object objectid} name ${object get\<string>('name')} geopoint ${object get\<parsegeopoint>('lastloginlocation') tojson()}'); 12 } 13 } wherewithingeobox 1 final querybuilder\<parseobject> parsequery = querybuilder\<parseobject>(parseobject('profile')); 2 parsequery wherewithingeobox( 3 'lastloginlocation', 4 parsegeopoint(latitude 37 38412167489413, longitude 122 01268034622319), 5 parsegeopoint(latitude 37 28412167489413, longitude 121 91268034622319) 6 ); 7 8 final apiresponse = await parsequery query(); 9 10 if (apiresponse success && apiresponse results != null) { 11 for (var object in apiresponse results as list\<parseobject>) { 12 print('${object objectid} name ${object get\<string>('name')} geopoint ${object get\<parsegeopoint>('lastloginlocation') tojson()}'); 13 } 14 } wherewithinkilometers 1 final querybuilder\<parseobject> parsequery = querybuilder\<parseobject>(parseobject('profile')); 2 parsequery wherewithinkilometers( 3 'lastloginlocation', 4 parsegeopoint(latitude 37 38412167489413, longitude 122 01268034622319), 5 100 6 ); 7 8 final apiresponse = await parsequery query(); 9 10 if (apiresponse success && apiresponse results != null) { 11 for (var object in apiresponse results as list\<parseobject>) { 12 print('${object objectid} name ${object get\<string>('name')} geopoint ${object get\<parsegeopoint>('lastloginlocation') tojson()}'); 13 } 14 } wherewithinmiles 1 final querybuilder\<parseobject> parsequery = querybuilder\<parseobject>(parseobject('profile')); 2 parsequery wherewithinmiles( 3 'lastloginlocation', 4 parsegeopoint(latitude 37 38412167489413, longitude 122 01268034622319), 5 100 6 ); 7 8 final apiresponse = await parsequery query(); 9 10 if (apiresponse success && apiresponse results != null) { 11 for (var object in apiresponse results as list\<parseobject>) { 12 print('${object objectid} name ${object get\<string>('name')} geopoint ${object get\<parsegeopoint>('lastloginlocation') tojson()}'); 13 } 14 } wherewithinradians 1 final querybuilder\<parseobject> parsequery = querybuilder\<parseobject>(parseobject('profile')); 2 parsequery wherewithinradians( 3 'lastloginlocation', 4 parsegeopoint(latitude 37 38412167489413, longitude 122 01268034622319), 5 100 6 ); 7 8 final apiresponse = await parsequery query(); 9 10 if (apiresponse success && apiresponse results != null) { 11 for (var object in apiresponse results as list\<parseobject>) { 12 print('${object objectid} name ${object get\<string>('name')} geopoint ${object get\<parsegeopoint>('lastloginlocation') tojson()}'); 13 } 14 } 分页这些方法与分页工具相关，适用于将检索大量结果的查询。 setamounttoskip 1 final querybuilder\<parseobject> parsequery = querybuilder\<parseobject>(parseobject('profile')); 2 parsequery setamounttoskip(2); 3 final apiresponse = await parsequery query(); 4 5 if (apiresponse success && apiresponse results != null) { 6 for (var object in apiresponse results as list\<parseobject>) { 7 print('${object objectid} name ${object get\<string>('name')}'); 8 } 9 } setlimit 1 final querybuilder\<parseobject> parsequery = querybuilder\<parseobject>(parseobject('profile')); 2 parsequery setlimit(2); 3 final apiresponse = await parsequery query(); 4 5 if (apiresponse success && apiresponse results != null) { 6 for (var object in apiresponse results as list\<parseobject>) { 7 print('${object objectid} name ${object get\<string>('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。 or //compose a compound query that is the or of the passed queries 1 final querybuilder\<parseobject> query1 = querybuilder\<parseobject>(parseobject('profile')); 2 query1 wheregreaterthan('friendcount', 10); 3 4 final querybuilder\<parseobject> query2 = querybuilder\<parseobject>(parseobject('profile')); 5 query2 wherelessthan('friendcount', 50); 6 7 querybuilder\<parseobject> 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\<parseobject>) { 16 print('${object objectid} name ${object get\<string>('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。