Flutter
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Data Queries
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 querybuilder 和 get get 从back4app检索单个 parseobject parseobject 。还有许多其他方法可以使用 querybuilder 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 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 (带有 插件 dart 和 flutter) 一个在 back4app 上 创建的应用 注意 请遵循 新 parse 应用教程 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 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 querybuilder 类的不同方法。 querybuilder 类 任何 parse 查询操作都使用 querybuilder 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 querybuilder ,您需要将所需的 parseobject 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 querybuilder 只有在调用检索方法 query 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 。 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 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 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 名称 日期类型 生日 生日 数字(整数)类型 好友数量 好友数量 数组(字符串列表)类型 最爱食物 最爱食物 数组(数字列表)类型 幸运数字 幸运数字 地理点类型 最后登录位置 最后登录位置 这是 parse object 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 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 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 options 作为附加参数,但在大多数情况下,它仅与 masterkey 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。