无法在for循环中使用JavaScript创建SQLite表 [英] Unable to CREATE SQLite tables using JavaScript in for loop
问题描述
我有一个使用AngularJS，JS，Phonegap/Cordova，Monaca和Onsen UI开发的跨平台应用程序.
I have a cross platform app developed using AngularJS, JS, Phonegap/Cordova, Monaca and Onsen UI.
我已经在应用程序中实现了一个SQLite数据库来存储各种数据，以确保可以离线使用该应用程序.我已经做了一些简单的测试，并且一切都按预期进行.
I have implemented a SQLite Database in the app to store various data to ensure that the app can be used offline. I have done a few simple tests and this is all working as intended.
我现在尝试在我的应用程序中首先查看的 onDeviceReady()函数创建该应用程序中需要的所有表(总共28个).为此，我创建了一个对象数组，该对象数组将一一传递给SQLite CREATE语句，如下所示.
I now try to create all the tables I will need in the app (28 in total) in my apps first views onDeviceReady() function. For this I create an array of objects that I will pass one by one to the SQLite CREATE statement as below.
设置表格值
// Form values
var formValues = [{
tablename: "table_1",
id: "id_1",
desc: "desc_1",
dataType: "TEXT"
}, {
tablename: "table_2",
id: "id_2",
desc: "desc_2",
dataType: "TEXT"
}, {
...
...
...
...
}, {
tablename: "table_28",
id: "id_28",
desc: "desc_28",
dataType: "TEXT"
}];
创建表格
function onDeviceReady() {
for (var i = 0; i < formValues.length; i++) {
var createFormValues = 'CREATE TABLE IF NOT EXISTS ' + formValues[i].tablename + ' (' + formValues[i].id + ' INTEGER, ' + formValues[i].desc + ' ' + formValues[i].dataType + ')';
alert("SQL: " + createFormValues +
"\n\nForm: " + formValues +
"\nName: " + formValues[i].tablename +
"\nID: " + formValues[i].id +
"\nDesc: " + formValues[i].desc +
"\nType: " + formValues[i].dataType);
db.transaction(function (tx) { tx.executeSql(createFormValues); });
}
};
运行上面的代码时，警报显示包括SQL语句在内的所有信息均正常.但是，当我在for()循环之后查询每个表时，它说没有 EXCEPT 最后一个表被创建.
When I run the above code, the alert shows that all the information including the SQL statement is OK. However, when I query each table following the for() loop, it says no tables are created EXCEPT the last table.
然后我尝试以下操作，它们执行创建所有表，但是效率和可管理性显然较低.
I then try the following which DOES create all the tables but is obviously less efficient and manageable.
调用函数
createFormTables("table_1", "id_1", "desc_1", "TEXT");
createFormTables("table_2", "id_2", "desc_2", "TEXT");
createFormTables("...", "...", "...", "...");
createFormTables("table_28", "id_28", "desc_28", "TEXT");
执行功能
createFormTables: function (tableName, id, description, dataType) {
var sql = 'CREATE TABLE IF NOT EXISTS ' + tableName + ' (' + id + ' INTEGER, ' + description + ' ' + dataType + ')';
alert("Create Form Field SQL: " + sql);
db.transaction(function (tx) { tx.executeSql(sql); });
},
我知道SQLite语句是异步执行的，但是我不明白为什么要在第二个示例而不是第一个示例中创建表?如何使用第一个示例创建表?我可以设置一个 $ timeout 来执行每个 INSERT 语句，但这似乎不必要，并且会导致延迟.
I know that the SQLite statements are executed asynchronously but I dont understand why that would create the tables in the second example and not the first? How do I create the tables using the first example? I can set a $timeout to execute each INSERT statement but this seems unnecessary and will cause delays.
推荐答案
在调用函数"createFormTables"时，我将使用JavaScript对象"方法避免冲突:
I would use the JavaScript "Object" aproach to avoid conflict when calling function 'createFormTables' with something like:
var QuerySet = function(){
//OPTIONAL: I use JQuery Deferred to catch when an async event has finished
this.defRes = new $.Deferred();
this.defResProm = this.defRes.promise();
};
QuerySet.prototype.createFormTables= function(inputData){
//do your stuff and manage when this.defRes is resolved and results it sends back (if a result is needed)
this.sqlToExecute = "// YOUR SQL QUERY";
var self=this;
$.when(
(new SqlResult(this.sqlToExecute)).execSqlCustomDeferred(), //read below for SqlResult() explanations
self
).done(function(sqlRes,self){
self.defRes.resolve();
});
return this.defResProm;
};
然后输入代码:
creatFromTables[i] = (new QuerySet()).createFormTables(inputData);
createFromTables[i].defRes.done(function(res){//do stuff with the result});
不需要使用$ .Deferred()，但我想如果您想知道何时创建了所有表，这可能会很有用.
Don't need to use $.Deferred() but I think it could be useful if you want to know when all the tables have been created.
这是sqlResult，用于在数据库本身上调用事务:
And here is sqlResult that is used to call the transaction on the DB itself:
var SqlResult = function(sqlToExecute,bracketValues){
//console.log("SqlResult("+sqlToExecute+','+bracketValues+') starts');
this.sqlToExecute = sqlToExecute;
this.bracketValues =bracketValues;
};
SqlResult.prototype.execSqlCustomDeferred = function(){
var execSqlCustomDeferredRes = $.Deferred();
var execSqlCustomDeferredResProm = execSqlCustomDeferredRes.promise();
//console.log("SqlResult.execSqlCustomDeferred sqlToExecute is: "+this.sqlToExecute);
var sqlToExecuteForTx = this.sqlToExecute;
var bracketValuesForTx = this.bracketValues;
DbManagement.db.transaction(function(tx){
console.log("SqlResult.execSqlCustomDeferred in TX sqlToExecute is: "+sqlToExecuteForTx);
if(bracketValuesForTx!=null){
console.log("SqlResult.execSqlCustomDeferred bracket value is: "+ArrayManagement.arrayToString(bracketValuesForTx));
}
tx.executeSql(sqlToExecuteForTx,bracketValuesForTx,success,error);
function success(tx,rs){
//console.log('before execSqlCustomDeferredRes resolve ' + execSqlCustomDeferredRes.state());
execSqlCustomDeferredRes.resolve(rs);
//console.log('before execSqlCustomDeferredRes resolve after ' + execSqlCustomDeferredRes.state());
}
function error(tx,error){
console.log('execSqlCustomDeferred error ' + error.message);
execSqlCustomDeferredRes.reject(error);
}
});
return execSqlCustomDeferredResProm;
};
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