主页 / coding / 问题 / 79173770
Accepted
Bineesh Kumar
Asked: 2024-11-10 05:55:39 +0800 CST

在 db.transaction 方法下的 while 循环内更新数组

  • 772

REACT NATIVE 疑问：尝试读取数据库并创建内容数组。在代码中，更新数组“rcpts”后，尝试访问 db.transaction 块外部时，它仍为空。如何真正更新该块内的数组？我问 bcz，似乎即使在 db.transaction 块的 while 循环内更新后，数组仍为空或保持其原始形式。

let rcpts = []

const db = SQLite.openDatabase('digit.db');
//date, agentNo, custName, custNo, paidAmount, custBalance, payMode, revGroup FROM tblRcpt ORDER BY Id DESC LIMIT 100 
function pushreceipts(){  
  let rcptlist =[];
  //Alert.alert("you clicked");
    db.transaction(tx=>{
      tx.executeSql("SELECT id,date, agentNo, custName, custNo, paidAmount, custBalance, payMode, revGroup FROM tblRcpt ORDER BY Id DESC LIMIT 100 ",
        null,(tx,result)=>{          
          let len = result.rows.length;
          if (len>0){
            for(let i =0;i<len;i++){
              let item = result.rows.item(i);              
              rcptlist.push({
                rcptNo : item.id,
                rcptdate : item.date,
                agentNo : item.agentNo,
                custName : item.custName,
                custNo : item.custNo,
                paidAmount : item.paidAmount,
                custBalance : item.custBalance,
                payMode : item.payMode,
                revGroup : item.revGroup
              });
              i++;
            } 
          }
          rcpts = rcptlist;
          Alert.alert("Data Push finished.")
          //Alert.alert("Survey Added");
        }),
        (error) =>{
          Alert.alert(error);
        }
      }
    )
    // **** Read the rcps Array and send using fetch here. ****
    let qty = rcpts.length;
    let i = 0;
    console.log(rcpts.length)
    while(i<qty+1){
      console.log('length of rcpts array'+rcpts.length);

      i++;
    }

  

}

react-native

1 个回答

  1. Best Answer

    回答你的问题；

    你正在提供一个回调，但尝试访问数组，而没有确保回调已被调用。你可以这样做：

    const db = SQLite.openDatabase('digit.db');

async function pushreceipts() {
  let rcpts = await new Promise((resolve, reject) =>
    db.transaction(tx => {
      tx.executeSql("SELECT id, date, agentNo, custName, custNo, paidAmount, custBalance, payMode, revGroup FROM tblRcpt ORDER BY Id DESC LIMIT 100 ",
        null, (tx, result) => {
          let len = result.rows.length;
          let res = [];
          if (len > 0) {
            for (let i = 0; i < len; i++) {
              let item = result.rows.item(i);
              res.push({
                rcptNo: item.id,
                rcptdate: item.date,
                agentNo: item.agentNo,
                custName: item.custName,
                custNo: item.custNo,
                paidAmount: item.paidAmount,
                custBalance: item.custBalance,
                payMode: item.payMode,
                revGroup: item.revGroup
              });
              i++;
            }
          }
          resolve(res);
        }),
        (error) => reject(error)
    }))
  // **** Read the rcps Array and send using fetch here. ****
  let qty = rcpts.length;
  let i = 0;
  console.log(rcpts.length)
  while (i < qty + 1) {
    console.log('length of rcpts array' + rcpts.length);
    i++;
  }
}

    但是，对于您要做的事情，更合适的解决方案是使用 Expo SQLite；

    import * as SQLite from 'expo-sqlite';

const allRows = await db.getAllAsync("SELECT id, date, agentNo, custName, custNo, paidAmount, custBalance, payMode, revGroup FROM tblRcpt ORDER BY Id DESC LIMIT 100");
for (const row of allRows) {
  console.log(row.id, row.value, row.intValue);
}
    • 1

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