I have a problem accessing the class properties after I call the updateUIFromDatabase() function.
Console.log says "startUpCount: undefined".
Before that, everything seemed to work (database returns 123 as it should when I call pump1.getValueFromDatabase("startUpCount")).
有人可以发现我在做什么错吗？
class PumpBasic
{
constructor(_name, _databaseTableName)
{
this.name = _name;
this.databaseTableName = _databaseTableName;
this.control = 0;
this.statusOfPump = 0;
this.feedback = 0;
this.motorPTC = 0;
this.dryRunProtection = 0;
this.workingHours = 0;
this.startUpCount = 0;
this.errorCount = 0;
this.feedbackTime = 0;
this.safeToRestart = 0;
this.unAckedError = 0;
this.timeSchedules = [];
}
getValueFromDatabase(variableNameInDatabase)
{
$.ajax({
url: "databaseValuesEnquiry.php",
method: "GET",
async: false,
data:{getDatabaseVariableValue:1 ,"variableNameInDatabase":variableNameInDatabase,"databaseTableName":this.databaseTableName},
success:function(response)
{
return response;
}
})
}
updateUIFromDatabase()
{
this.control = this.getValueFromDatabase("control");
this.statusOfPump = this.getValueFromDatabase("statusOfPump");
this.feedback = this.getValueFromDatabase("feedback");
this.motorPTC = 0;
this.dryRunProtection = 0;
this.workingHours = 0;
this.startUpCount = this.getValueFromDatabase("startUpCount");
this.errorCount = 0;
this.feedbackTime = 0;
this.safeToRestart = 0;
this.unAckedError = 0;
this.timeSchedules = [];
}
}
pump1 =new PumpBasic("pump1", "pump1settingstry");
pump1.getValueFromDatabase("workingHours");
pump1.updateUIFromDatabase();
console.log("startUpCount: ", pump1.startUpCount);
让我们看一下这段代码：
Here you call
getValueFromDatabaseseveral times. I never worked directly withjQuerybut this block表示您正在向后端发出请求。好吧，javascript就像快速，就像超级快速。您向后端发送请求，当请求返回已执行的其余代码时。这就是为什么您不确定的原因。
The function
getValueFromDatabasewill return aPromise(you can read more about it here: https://developer.mozilla.org/pt-BR/docs/Web/JavaScript/Reference/Global_Objects/Promise).好吧，由于它返回了一个承诺（将来会发生的事情），因此您需要拨打电话，等待电话解决，然后再执行其余需要做的事情。
在这种情况下，它将类似于：
The
awaitkeyword is just a keyword to say to the javascript engine: 'Hey man, could you please stop the execution of this code until this promise is resolved?'If you would like to learn more about the
awaitkeyword you can read it here: https://developer.mozilla.org/pt-BR/docs/Web/JavaScript/Reference/Operators/await我希望这不是宽松的，但我希望你能对诺言有所了解