如何在 ionic 2/3 中处理数据库异步操作 [英] How to handle database asynchronous operation in ionic 2/3

问题描述

我正在使用 ionic 中的数据库，我调用了一个返回许多记录的 API，我必须将这些记录插入数据库以及何时完成插入操作然后我想要从数据库中调用选择记录.问题是异步行为，在插入操作完成之前调用数据库中的选择记录.谁能帮我解决这个问题?我的代码在下面...

I am working with the database in ionic, I call one API that returns me a number of records, I have to insert those records into the database and when to insert operations are completed then I want to call select records from the database. problem is asynchronous behavior, the select records from the database called before the insert operations are completed. can anyone help me to resolve this? my code is below...

数据库提供者:

export class DbProvider {


  public addData(dId: string, sId: string, subId: string, subName: string,
    dDate: string, cId: string, cName: string, stdId: string, stdName: string,
  ) {
    return new Promise((resolve, reject) => {
      this.db.executeSql("INSERT INTO data (dId , sId , subId , subName ," +
        " dDate , cId , cName , stdId , stdName ) VALUES (?, ?,?, ?,?, ?,?, ?,?)",
        [dId, sId, subId, subName, dDate, cId, cName, stdId, stdName]).then((data) => {
          resolve(data);
        }, (error) => {
          reject(error.tostring());
        });
    });
  }

}

数据库插入和调用

for (let temp of ApiData) {

  this.DbHandler.IsAvailable(temp.dId).then(data => {


    if (data) {
      console.log("did Available editing " + data);

      this.DbHandler.editData(temp.dId, temp.sId, temp.subId, temp.subName,
        temp.dDate, temp.cId, temp.cName);


    } else {
      console.log("did not Available inserting " + data);

      this.DbHandler.addData(temp.dId, temp.sId, temp.subId, temp.subName,
        temp.dDate, temp.cId, temp.cName);

    }
  });
}

this.getDataFromDb();

在开始 SELECT 请求之前，我想完成多个 INSERT.我的问题是 SELECT 触发时 INSERT 尚未完成.

I have multiple INSERTs I'd like to be done before starting SELECT requests. My problem is that the INSERT is not yet finished when the SELECT fires.

推荐答案

在then方法中调用read from DB:

Call read from DB in then method:

let promises = [];
for (let temp of ApiData) {
  let promise = new Promise((resolve, reject) => {
    this.DbHandler.IsAvailable(temp.dId).then(data => {
      if (data) {
        console.log("did Available editing " + data);
        this.DbHandler.editData(temp.dId, temp.sId, temp.subId, temp.subName,
          temp.dDate, temp.cId, temp.cName).then(() => resolve());
      } else {
        console.log("did not Available inserting " + data);
        this.DbHandler.addData(temp.dId, temp.sId, temp.subId, temp.subName,
          temp.dDate, temp.cId, temp.cName).then(() => resolve());
      }
    });
  };
  promises.push(promise);
}
Promise.all(promises).then(() => this.getDataFromDb());

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