React NativeでのParseユーザークエリ操作ガイド

react nativeでparseのユーザーをクエリする はじめに いくつかのreact nativeアプリは、アプリケーションのユーザーを直接管理する必要があるか、少なくとも特定のサブセットをリストできる必要があります。parseには強力なクエリツールがあり、例えばソーシャルメディアアプリのユーザーにも使用できます。 このガイドでは、 parse query parse query を使用して、parse js sdkを使用したreact nativeアプリで現実的なユーザークエリを実行する方法を学びます。 前提条件 このチュートリアルを完了するには、 作成されたreact nativeアプリと https //www back4app com/docs/react native/parse sdk/react native sdk 目標 react nativeアプリのためにparseを使用してユーザークエリ機能を構築すること。 1 parse queryクラスの理解 任意のparseクエリ操作は、 parse query parse query オブジェクトタイプを使用し、アプリ全体でデータベースから特定のデータを取得するのに役立ちます。 parse query parse query は、リトリーブメソッド（例えば、 parse query find parse query find または parse query get parse query get ）を呼び出した後にのみ解決されるため、クエリを設定し、実際に呼び出される前にいくつかの修飾子をチェーンすることができます。 新しい parse query parse query を作成するには、クエリ結果を含む parse object parse object サブクラスをパラメータとして渡す必要があります。このガイドのユースケースの例（ parse user parse user ）は以下に示されています。 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(); 次のことについてもっと読むことができます。 parse query parse query クラスは、 https //parseplatform org/parse sdk js/api/master/parse query html 。 2 関連するユーザークエリの実行 アプリでユーザーを管理または表示する際に実行する必要があるいくつかの関連クエリを見てみましょう。まず、検索値を含むユーザー名を持つユーザーを検索するテキスト検索クエリを実行しましょう。 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 }; 文字列を検索する方法は少なくとも2つあり、それぞれ特定の用途と利点があります。ほとんどの場合、あなたは parse query matches parse query matches を使用して、大文字小文字を区別しない結果を確保し、コード内での予期しない動作を避けることを望むでしょう。 このクエリを実行した後、アプリのユーザーリストには次のようなものが表示されるはずです 文字列クエリに加えて、ブールフィールドと同様に、正確な値を含むオブジェクトを取得したい場合には「正確な」クエリを実行することもできます。次の例では、 emailverified emailverified フィールドを通じて、メールで確認されたユーザーを取得する方法を示します。 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 }; あなたのアプリは今、ユーザーリストをこのように更新するはずです 別の一般的な例は、クエリに順序を適用することです。これは2つの方法で行うことができます。まずは parse query ascending/parse query descending parse query ascending/parse query descending または parse query addascending/parse query adddescending parse query addascending/parse query adddescending です。最初のケースは他の順序を上書きし、クエリが取る唯一のものになります。後者は既存の順序と連結し、複数の順序を可能にします。 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 }; あなたのアプリは今、クエリを次のように順序付ける必要があります 上記のすべてのクエリ制約は連鎖させて単一のクエリで実行できることを忘れないでください。これにより、異なるフィルターや並べ替えを作成するためのアプリの使いやすさが向上します。以下は、このガイドで使用されているすべてのクエリメソッドを示す完全なコードです 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 }; 結論 このガイドの最後に、react nativeでparseユーザーに対してクエリを実行する方法を学びました。次のガイドでは、parseでデータを保存し、読み取る方法を示します。