Consultas avanzadas de usuarios en Parse con React Native

consultando usuarios en parse en react native introducción algunas aplicaciones de react native necesitan gestionar directamente a los usuarios de su aplicación o al menos poder listar un subconjunto específico de ellos parse tiene herramientas de consulta poderosas y también se pueden usar para tus usuarios en tu aplicación de redes sociales, por ejemplo en esta guía, aprenderás a usar parse query parse query para realizar consultas realistas de usuarios en tu aplicación de react native utilizando el sdk de parse js requisitos previos para completar este tutorial, necesitarás una aplicación de react native creada y conectada a back4app objetivo construir una función de consulta de usuarios utilizando parse para una aplicación de react native 1 entendiendo la clase parse query cualquier operación de consulta de parse utiliza el parse query parse query tipo de objeto, que te ayudará a recuperar datos específicos de tu base de datos a lo largo de tu aplicación es crucial saber que un parse query parse query solo se resolverá después de llamar a un método de recuperación (como parse query find parse query find o parse query get parse query get ), por lo que se puede configurar una consulta y encadenar varios modificadores antes de ser realmente llamada para crear un nuevo parse query parse query , necesitas pasar como parámetro la parse object parse object deseada, que es la que contendrá los resultados de tu consulta un ejemplo para este caso de uso de la guía ( parse user parse user ) se puede ver a continuación javascript 1 // this will create your query 2 const parsequery = new parse query(parse user); 3 // the query will resolve only after calling this method 5 const queryresult = await parsequery find();1 // this will create your query 2 const parsequery parse query = new parse query(parse user); 3 // the query will resolve only after calling this method 4 const queryresult \[parse user] = await parsequery find(); puedes leer más sobre la parse query parse query clase aquí en la documentación oficial https //parseplatform org/parse sdk js/api/master/parse query html 2 realizando consultas de usuario relevantes ahora echemos un vistazo a algunas consultas relevantes que puede necesitar realizar al gestionar o mostrar usuarios en su aplicación primero que nada, realicemos una consulta de búsqueda de texto, buscando usuarios cuyos nombres de usuario contengan el valor de búsqueda javascript 1 const douserquery = async function () { 2 // this value comes from a state variable 3 const usernamesearchvalue = usernamesearch; 4 // this will create your user query 5 const parsequery = new parse query(parse user); 6 // several query functions can be set to your parse,query, they will 7 // only resolve when calling "find", for example 8 if (usernamesearchvalue !== '') { 9 // "contains" will retrieve users whose username contain the searched value, case sensitive 10 parsequery contains('username', usernamesearchvalue); 11 // 12 // or 13 // 14 // for case insensitive string search, use "matches", that will take into account 15 // an regexp for matching, in this case use only "i", which is the regexp modifier 16 // for case insensitive 17 parsequery matches('username', usernamesearchvalue, 'i'); 18 } 19 // only after calling "find" all query conditions will resolve 20 return await parsequery 21 find() 22 then(async (queriedusers => { 23 // set the query results to an state variable to retrieve it on your jsx 24 // be aware that empty or invalid queries return as an empty array 25 setqueryresults(queriedusers); 26 return true; 27 }) 28 catch((error) => { 29 // error can be caused by lack of internet connection, but in most 30 // cases "find" will return as an empty array on "then" 31 alert alert('error!', error message); 32 setqueryresults(\[]); 33 return false; 34 }); 35 };1 const douserquery = async function () promise\<boolean> { 2 // this value comes from a state variable 3 const usernamesearchvalue string = usernamesearch; 4 // this will create your user query 5 const parsequery parse query = new parse query(parse user); 6 // several query functions can be set to your parse,query, they will 7 // only resolve when calling "find", for example 8 if (usernamesearchvalue !== '') { 9 // "contains" will retrieve users whose username contain the searched value, case sensitive 10 parsequery contains('username', usernamesearchvalue); 11 // 12 // or 13 // 14 // for case insensitive string search, use "matches", that will take into account 15 // an regexp for matching, in this case use only "i", which is the regexp modifier 16 // for case insensitive 17 parsequery matches('username', usernamesearchvalue, 'i'); 18 } 19 // only after calling "find" all query conditions will resolve 20 return await parsequery 21 find() 22 then(async (queriedusers \[parse user]) => { 23 // set the query results to an state variable to retrieve it on your jsx 24 // be aware that empty or invalid queries return as an empty array 25 setqueryresults(queriedusers); 26 return true; 27 }) 28 catch((error object) => { 29 // error can be caused by lack of internet connection, but in most 30 // cases "find" will return as an empty array on "then" 31 alert alert('error!', error message); 32 setqueryresults(\[]); 33 return false; 34 }); 35 }; tenga en cuenta que hay al menos dos formas diferentes de buscar una cadena, cada una con sus aplicaciones y ventajas específicas en la mayoría de los casos, querrá usar parse query matches parse query matches para garantizar resultados que no distingan entre mayúsculas y minúsculas y evitar comportamientos inesperados en su código después de realizar esta consulta, su lista de usuarios en su aplicación debería mostrar algo como esto además de la consulta de cadenas, también puede realizar consultas “exactas”, cuando desea recuperar objetos que contengan un valor exacto, al igual que con los campos booleanos el siguiente ejemplo mostrará cómo recuperar usuarios que están verificados por correo electrónico, a través del emailverified emailverified campo javascript 1 const douserquery = async function () { 2 // this value comes from a state variable 3 const showonlyverifiedvalue boolean = showonlyverified; 4 // this will create your user query 5 const parsequery = new parse query(parse user); 6 // several query functions can be set to your parse,query, they will 7 // only resolve when calling "find", for example 8 if (showonlyverifiedvalue === true) { 9 // "equalto" will retrieve users whose "emailverified" value is exactly "true" 10 parsequery equalto('emailverified', true); 11 } 12 // only after calling "find" all query conditions will resolve 13 return await parsequery 14 find() 15 then(async (queriedusers) => { 16 // set the query results to an state variable to retrieve it on your jsx 17 // be aware that empty or invalid queries return as an empty array 18 setqueryresults(queriedusers); 19 return true; 20 }) 21 catch((error) => { 22 // error can be caused by lack of internet connection, but in most 23 // cases "find" will return as an empty array on "then" 24 alert alert('error!', error message); 25 setqueryresults(\[]); 26 return false; 27 }); 28 };1 const douserquery = async function () promise\<boolean> { 2 // this value comes from a state variable 3 const showonlyverifiedvalue boolean = showonlyverified; 4 // this will create your user query 5 const parsequery parse query = new parse query(parse user); 6 // several query functions can be set to your parse,query, they will 7 // only resolve when calling "find", for example 8 if (showonlyverifiedvalue === true) { 9 // "equalto" will retrieve users whose "emailverified" value is exactly "true" 10 parsequery equalto('emailverified', true); 11 } 12 // only after calling "find" all query conditions will resolve 13 return await parsequery 14 find() 15 then(async (queriedusers \[parse user]) => { 16 // set the query results to an state variable to retrieve it on your jsx 17 // be aware that empty or invalid queries return as an empty array 18 setqueryresults(queriedusers); 19 return true; 20 }) 21 catch((error object) => { 22 // error can be caused by lack of internet connection, but in most 23 // cases "find" will return as an empty array on "then" 24 alert alert('error!', error message); 25 setqueryresults(\[]); 26 return false; 27 }); 28 }; tu aplicación ahora debería estar actualizando tu lista de usuarios así otro ejemplo común sería aplicar ordenamientos a tu consulta esto se puede hacer de dos maneras, ya sea utilizando parse query ascending/parse query descending parse query ascending/parse query descending o parse query addascending/parse query adddescending parse query addascending/parse query adddescending el primer caso anulará cualquier otro ordenamiento y será el único que la consulta tomará, y el último se concatenará con los ordenamientos existentes, haciendo posibles múltiples ordenamientos javascript 1 const douserquery = async function () { 2 // this value comes from a state variable 3 const orderbyvalue = orderby; 4 // this will create your user query 5 const parsequery = new parse query(parse user); 6 // several query functions can be set to your parse,query, they will 7 // only resolve when calling "find", for example 8 // for list ordering, you can use "addascending" or "adddescending", passing as parameter 9 // which object field should be the one to order by 10 // note that "usernameasc", "usernamedesc" and so on are made up string values applied to a filter in 11 // our example app, so change it by what is suitable to you 12 if (orderbyvalue === 'usernameasc') { 13 parsequery ascending('username'); 14 // 15 // or 16 // 17 parsequery addascending('username'); 18 } else if (orderbyvalue === 'usernamedesc') { 19 parsequery descending('username'); 20 // 21 // or 22 // 23 parsequery adddescending('username'); 24 } else if (orderbyvalue === 'dateasc') { 25 parsequery ascending('createdat'); 26 // 27 // or 28 // 29 parsequery addascending('createdat'); 30 } else if (orderbyvalue === 'datedesc') { 31 parsequery descending('createdat'); 32 // 33 // or 34 // 35 parsequery adddescending('createdat'); 36 } 37 // only after calling "find" all query conditions will resolve 38 return await parsequery 39 find() 40 then(async (queriedusers) => { 41 // set the query results to an state variable to retrieve it on your jsx 42 // be aware that empty or invalid queries return as an empty array 43 setqueryresults(queriedusers); 44 return true; 45 }) 46 catch((error) => { 47 // error can be caused by lack of internet connection, but in most 48 // cases "find" will return as an empty array on "then" 49 alert alert('error!', error message); 50 setqueryresults(\[]); 51 return false; 52 }); 53 };1 const douserquery = async function () promise\<boolean> { 2 // this value comes from a state variable 3 const orderbyvalue string = orderby; 4 // this will create your user query 5 const parsequery parse query = new parse query(parse user); 6 // several query functions can be set to your parse,query, they will 7 // only resolve when calling "find", for example 8 // for list ordering, you can use "addascending" or "adddescending", passing as parameter 9 // which object field should be the one to order by 10 // note that "usernameasc", "usernamedesc" and so on are made up string values applied to a filter in 11 // our example app, so change it by what is suitable to you 12 if (orderbyvalue === 'usernameasc') { 13 parsequery ascending('username'); 14 // 15 // or 16 // 17 parsequery addascending('username'); 18 } else if (orderbyvalue === 'usernamedesc') { 19 parsequery descending('username'); 20 // 21 // or 22 // 23 parsequery adddescending('username'); 24 } else if (orderbyvalue === 'dateasc') { 25 parsequery ascending('createdat'); 26 // 27 // or 28 // 29 parsequery addascending('createdat'); 30 } else if (orderbyvalue === 'datedesc') { 31 parsequery descending('createdat'); 32 // 33 // or 34 // 35 parsequery adddescending('createdat'); 36 } 37 // only after calling "find" all query conditions will resolve 38 return await parsequery 39 find() 40 then(async (queriedusers \[parse user]) => { 41 // set the query results to an state variable to retrieve it on your jsx 42 // be aware that empty or invalid queries return as an empty array 43 setqueryresults(queriedusers); 44 return true; 45 }) 46 catch((error object) => { 47 // error can be caused by lack of internet connection, but in most 48 // cases "find" will return as an empty array on "then" 49 alert alert('error!', error message); 50 setqueryresults(\[]); 51 return false; 52 }); 53 }; tu aplicación ahora debe estar ordenando tus consultas de esta manera recuerda que todas las restricciones de consulta mencionadas anteriormente se pueden encadenar y realizar en una sola consulta, mejorando la usabilidad de tu aplicación para crear diferentes filtros y ordenamientos que funcionarán juntos aquí está el código completo que presenta todos los métodos de consulta utilizados en esta guía javascript 1 const douserquery = async function () { 2 // this value comes from a state variable 3 const usernamesearchvalue = usernamesearch; 4 const showonlyverifiedvalue = showonlyverified; 5 const orderbyvalue = orderby; 6 // this will create your user query 7 const parsequery = new parse query(parse user); 8 // several query functions can be set to your parse,query, they will 9 // only resolve when calling "find", for example 10 if (usernamesearchvalue !== '') { 11 // "contains" will retrieve users whose username contain the searched value, case sensitive 12 parsequery contains('username', usernamesearchvalue); 13 // 14 // or 15 // 16 // for case insensitive string search, use "matches", that will take into account 17 // an regexp for matching, in this case use only "i", which is the regexp modifier 18 // for case insensitive 19 parsequery matches('username', usernamesearchvalue, 'i'); 20 } 21 if (showonlyverifiedvalue === true) { 22 // "equalto" will retrieve users whose "emailverified" value is exactly "true" 23 parsequery equalto('emailverified', true); 24 } 25 // for list ordering, you can use "addascending" or "adddescending", passing as parameter 26 // which object field should be the one to order by 27 if (orderbyvalue === 'usernameasc') { 28 parsequery ascending('username'); 29 // 30 // or 31 // 32 parsequery addascending('username'); 33 } else if (orderbyvalue === 'usernamedesc') { 34 parsequery descending('username'); 35 // 36 // or 37 // 38 parsequery adddescending('username'); 39 } else if (orderbyvalue === 'dateasc') { 40 parsequery ascending('createdat'); 41 // 42 // or 43 // 44 parsequery addascending('createdat'); 45 } else if (orderbyvalue === 'datedesc') { 46 parsequery descending('createdat'); 47 // 48 // or 49 // 50 parsequery adddescending('createdat'); 51 } 52 // only after calling "find" all query conditions will resolve 53 return await parsequery 54 find() 55 then(async (queriedusers) => { 56 // set the query results to an state variable to retrieve it on your jsx 57 // be aware that empty or invalid queries return as an empty array 58 setqueryresults(queriedusers); 59 return true; 60 }) 61 catch((error) => { 62 // error can be caused by lack of internet connection, but in most 63 // cases "find" will return as an empty array on "then" 64 alert alert('error!', error message); 65 setqueryresults(\[]); 66 return false; 67 }); 68 };1 const douserquery = async function () promise\<boolean> { 2 // this value comes from a state variable 3 const usernamesearchvalue string = usernamesearch; 4 const showonlyverifiedvalue boolean = showonlyverified; 5 const orderbyvalue string = orderby; 6 // this will create your user query 7 const parsequery parse query = new parse query(parse user); 8 // several query functions can be set to your parse,query, they will 9 // only resolve when calling "find", for example 10 if (usernamesearchvalue !== '') { 11 // "contains" will retrieve users whose username contain the searched value, case sensitive 12 parsequery contains('username', usernamesearchvalue); 13 // 14 // or 15 // 16 // for case insensitive string search, use "matches", that will take into account 17 // an regexp for matching, in this case use only "i", which is the regexp modifier 18 // for case insensitive 19 parsequery matches('username', usernamesearchvalue, 'i'); 20 } 21 if (showonlyverifiedvalue === true) { 22 // "equalto" will retrieve users whose "emailverified" value is exactly "true" 23 parsequery equalto('emailverified', true); 24 } 25 // for list ordering, you can use "addascending" or "adddescending", passing as parameter 26 // which object field should be the one to order by 27 if (orderbyvalue === 'usernameasc') { 28 parsequery ascending('username'); 29 // 30 // or 31 // 32 parsequery addascending('username'); 33 } else if (orderbyvalue === 'usernamedesc') { 34 parsequery descending('username'); 35 // 36 // or 37 // 38 parsequery adddescending('username'); 39 } else if (orderbyvalue === 'dateasc') { 40 parsequery ascending('createdat'); 41 // 42 // or 43 // 44 parsequery addascending('createdat'); 45 } else if (orderbyvalue === 'datedesc') { 46 parsequery descending('createdat'); 47 // 48 // or 49 // 50 parsequery adddescending('createdat'); 51 } 52 // only after calling "find" all query conditions will resolve 53 return await parsequery 54 find() 55 then(async (queriedusers \[parse user]) => { 56 // set the query results to an state variable to retrieve it on your jsx 57 // be aware that empty or invalid queries return as an empty array 58 setqueryresults(queriedusers); 59 return true; 60 }) 61 catch((error object) => { 62 // error can be caused by lack of internet connection, but in most 63 // cases "find" will return as an empty array on "then" 64 alert alert('error!', error message); 65 setqueryresults(\[]); 66 return false; 67 }); 68 }; conclusión al final de esta guía, aprendiste cómo realizar consultas sobre usuarios de parse en react native en la próxima guía, te mostraremos cómo guardar y leer datos en parse