为什么db.transaction不能用于indexeddb？

问题描述

我是使用inxededdb的新手，并试图从商店获取数据。商店包含数据，但由于某些原因，代码在尝试设置var tx后停止。如果我缺少任何东西，请告诉我。这里是我试图拿到这本书的函数：

pre $函数getBook（）{
var tx = db.transaction（book，readonly）;
var store = tx.objectStore（book）;
var index = store.index（by_getid）;

var request = index.get（<？php echo $ _GET ['book']？>）;
request.onsuccess = function（）{
var matching = request.result;
if（matching！== undefined）{
document.getElementById（text-container）。innerHTML = matching.text;
} else {
alert（'no match'）;
report（null）;
}
};

解决的版本：

  function getBook（）{
 var db; 
 var request = indexedDB.open（library，1）; 
 
 request.onsuccess = function（evt）{
 db = request.result; 
 var transaction = db.transaction（[book]）; 
 var objectStore = transaction.objectStore（book）; 
 var requesttrans = objectStore.get（<？php echo $ _GET ['book']？>）; 
 
 requesttrans.onerror =函数（事件）{
 
}; 
 
 requesttrans.onsuccess = function（event）{
 alert（requesttrans.result.text）; 
}; 
 
}; 
} 
  

解决方案

变量。您可能正在访问连接对象的关闭或空实例。

尝试在函数内部创建数据库连接。不要使用全局数据库变量。

I am new at using inxededdb and am trying to get data out of a store. The store contains data, but for some reason the code stops after trying to set the var tx. If I am missing anything please let me know. Here is the function with which I am trying to get the book:

function getBook(){
    var tx = db.transaction("book", "readonly");
    var store = tx.objectStore("book");
    var index = store.index("by_getid");

    var request = index.get("<?php echo $_GET['book'] ?>");
    request.onsuccess = function() {
      var matching = request.result;
      if (matching !== undefined) {
         document.getElementById("text-container").innerHTML = matching.text;
      } else {
        alert('no match');
        report(null);
      }
    };
}

Solved Version:

function getBook(){
    var db;
    var request = indexedDB.open("library", 1);

    request.onsuccess = function (evt) {
    db = request.result;
    var transaction = db.transaction(["book"]);
    var objectStore = transaction.objectStore("book");
    var requesttrans = objectStore.get(<?php echo $_GET['book'] ?>);

        requesttrans.onerror = function(event) {

        };

        requesttrans.onsuccess = function(event) {
            alert(requesttrans.result.text);
        };

    };
}

解决方案

The problem is probably your db variable. You are probably accessing a closed or null instance of a connection object.

Try instead to create the db connection right inside the function. Do NOT use a global db variable.

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