Question

react-native-sqlite 值不显示

2021-01-21

65

android ios react-native sqlite react-native-sqlite-storage

this.getDetails();

getDetails = () => {
     let userDetails = [];
     db.transaction((tx) => {
          tx.executeSql('select * from users where role=?',['students'],(tx,results) => {
               let details = []
               if(results.rows.length > 0){
                    for(let i=0; i < results.rows.length; i++){
                          details.push(results.rows.item(i));
                    }
               }
               userDetails = details;
               //Data is displayed  here
               console.log(userDetails)
          })
     })
     // Data is not printed here
     console.log(userDetails) // []
}

在上面的代码片段中，我能够获取 tx.executeSql 内部的数据（userDetails），但不能获取 db.transaction 块外部的数据。

有人可以帮我解决如何在 db.transaction 块之外显示数据吗？

Answer 1

定义一个 promise 函数，用于从 DB 获取 userDetails 。

async dbAction = () => {
  return new Promise((resolve, reject) => {
    db.transaction((tx) => {
          tx.executeSql('select * from users where role=?',['students'],(tx,results) => {
               let details = []
               if(results.rows.length > 0){
                    for(let i=0; i < results.rows.length; i++){
                          details.push(results.rows.item(i));
                    }
               }
               //Data is displayed  here
               resolve(details);
          })
     })
  });
}

然后你可以像这样调用它。

getDetails = () => {
     let userDetails = [];
     try {
       let userDetails = await dbAction();
       console.log(userDetails);
     } catch (e) {
     }
}