为什么一个打字稿的实例首先执行GET和GET中的代码之后

Question

这是我的调用

let sqlLocalSelect = new SqlLocalSelect();
var variable = sqlLocalSelect;
console.log("variable " + JSON.stringify(variable));

这是我称的类

import { SQLite } from 'ionic-native';
export class SqlLocalSelect {
database: SQLite;
private li_sitios: Array<Object> = [];
constructor() {}
get get_li_sitios(): Array<Object> {
this.database = new SQLite();
this.database.openDatabase({name: "data.db", location: "default"}).then(() => {
  this.database.executeSql('SELECT * FROM Markers;', [])
  .then((data) => {
    if(data.rows.length > 0){
      this.li_sitios = [];
      for(var i = 0; i < data.rows.length; i++) {
        var value:string = "no";
        if (data.rows.item(i).synchronised) {
          value = "si";
        } else {
          value = "no";
        }
        this.li_sitios.unshift({
          id: data.rows.item(i).id, 
          id_externa: data.rows.item(i).id_externa,
          id_owner: data.rows.item(i).id_owner, 
          name: data.rows.item(i).name, 
          lat: data.rows.item(i).lat, 
          lng: data.rows.item(i).lng,
          draggable: false, 
          synchronised: value,
          fecha: data.rows.item(i).fecha,
          hora: data.rows.item(i).hora
        });
      }
    } else {
      console.log("No se encontraron datos");
    }
    console.log("Consulta realizada correctamente");
    console.log("li_sitios "+ JSON.stringify(this.li_sitios));
  }, (error) => {
    console.log("Error ejecutando la consulta: " + JSON.stringify(error));
  });
  }, (error) => {
    console.log("Error al conectar con la base de datos local: " + JSON.stringify(error));
  });
  return this.li_sitios;
  }
}

基本上，它是对SQLite数据库的查询，但是数据输出不会以正确的顺序运行

这是我的输出

06-07 18:23:51.030 21450-21450/io.ionic.starter I/chromium: [INFO:CONSOLE(60258)] "variable []", source: file:///android_asset/www/build/main.js (60258) 06-07 18:23:51.120 21450-21450/io.ionic.starter I/chromium: [INFO:CONSOLE(179)] "OPEN database: data.db - OK", source: file:///android_asset/www/plugins/cordova-sqlite-storage/www/SQLitePlugin.js (179) 06-07 18:23:51.240 21450-21555/io.ionic.starter W/System.err: java.sql.SQLException: sqlite3_step failure: cannot rollback - no transaction is active 06-07 18:23:51.240 21450-21555/io.ionic.starter W/System.err: at io.liteglue.SQLiteGlueConnection$SQLGStatement.step(SQLiteGlueConnection.java:135) 06-07 18:23:51.240 21450-21555/io.ionic.starter W/System.err: at io.sqlc.SQLiteConnectorDatabase.executeSQLiteStatement(SQLiteConnectorDatabase.java:214) 06-07 18:23:51.240 21450-21555/io.ionic.starter W/System.err: at io.sqlc.SQLiteConnectorDatabase.executeSqlBatch(SQLiteConnectorDatabase.java:114) 06-07 18:23:51.240 21450-21555/io.ionic.starter W/System.err: at io.sqlc.SQLitePlugin$DBRunner.run(SQLitePlugin.java:340) 06-07 18:23:51.240 21450-21555/io.ionic.starter W/System.err: at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1112) 06-07 18:23:51.240 21450-21555/io.ionic.starter W/System.err: at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:587) 06-07 18:23:51.240 21450-21555/io.ionic.starter W/System.err: at java.lang.Thread.run(Thread.java:831) 06-07 18:23:51.240 21450-21555/io.ionic.starter W/System.err: java.sql.SQLException: sqlite3_step failure: cannot rollback - no transaction is active 06-07 18:23:51.240 21450-21555/io.ionic.starter W/System.err: at io.liteglue.SQLiteGlueConnection$SQLGStatement.step(SQLiteGlueConnection.java:135) 06-07 18:23:51.240 21450-21555/io.ionic.starter W/System.err: at io.sqlc.SQLiteConnectorDatabase.executeSQLiteStatement(SQLiteConnectorDatabase.java:214) 06-07 18:23:51.240 21450-21555/io.ionic.starter W/System.err: at io.sqlc.SQLiteConnectorDatabase.executeSqlBatch(SQLiteConnectorDatabase.java:114) 06-07 18:23:51.240 21450-21555/io.ionic.starter W/System.err: at io.sqlc.SQLitePlugin$DBRunner.run(SQLitePlugin.java:340) 06-07 18:23:51.240 21450-21555/io.ionic.starter W/System.err: at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1112) 06-07 18:23:51.240 21450-21555/io.ionic.starter W/System.err: at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:587) 06-07 18:23:51.240 21450-21555/io.ionic.starter W/System.err: at java.lang.Thread.run(Thread.java:831) 06-07 18:23:51.290 21450-21450/io.ionic.starter I/chromium: [INFO:CONSOLE(60834)] "Consulta realizada correctamente", source: file:///android_asset/www/build/main.js (60834) 06-07 18:23:51.290 21450-21450/io.ionic.starter I/chromium: [INFO:CONSOLE(60835)] "li_sitios [{"id":4,"id_externa":0,"id_owner":1,"name":"Nombre 4","lat":22.834722222222,"lng":-103.91194444444,"draggable":false,"synchronised":"si","fecha":"2017-6-5","hora":"15:36"},{"id":3,"id_externa":0,"id_owner":1,"name":"Nombre 2","lat":22.534722222222,"lng":-103.91194444444,"draggable":false,"synchronised":"si","fecha":"2017-6-5","hora":"15:29"},{"id":2,"id_externa":15,"id_owner":1,"name":"Nombre 2","lat":22.534722222222,"lng":-103.91194444444,"draggable":false,"synchronised":"no","fecha":"2017-6-5","hora":"15:24"},{"id":1,"id_externa":16,"id_owner":1,"name":"Nombre 1","lat":22.034722222222,"lng":-103.91194444444,"draggable":false,"synchronised":"no","fecha":"2017-6-5","hora":"15:22"}]", source: file:///android_asset/www/build/main.js (60835)

我首先提到的是，它似乎是空白的结果，然后查询的结果扔向控制台。

Answer 1

我首先提到的是，它似乎是get never的结果，然后查询的结果将其扔向控制台。

这是异步编程的本质。与简化的示例非常相似：

const arr = [];
setTimeout(()=>{
   arr.push(1);
   console.log(arr); // [1]
}, 1000);
console.log(arr); // []

按行号编码订单不一定是执行顺序。这听起来很简单(确实如此(，但是我们看到很多初学者都缺少它值得一提的。

Answer 2

非常感谢您，我在您的帮助下解决了它

  this.sqlLocalSelect = new SqlLocalSelect();
  setTimeout(()=>{
    var variable = this.sqlLocalSelect.get_li_sitios;
    console.log("variable " + JSON.stringify(variable));
  }, 1000);