jQuery 以错误的顺序执行代码部分

Question

我目前正在为我的叔叔做一个项目，他是一名兽医。这是一个电子项目，让他可以管理他的客户、病人和他们的访问。然而，在使用一段时间后，我们意识到，有时 ipcRenderer 在尝试插入新客户、患者或约会时会触发两次，甚至更多次。我试图通过添加另一个 sql 查询来捕获这一点，该查询检查是否有相同的记录，我想要插入的内容已经在数据库中。但是现在，每当我尝试插入新记录时， db.all() （起初是 db.run() ，在过去的几个小时里，我一直在尝试通过反复试验来修复并且绝望了）哪个插入记录在 db.all() 之前执行，它获取相同记录的数量并设置计数器，尽管它应该在之后执行。我尝试使用 $.when() 和 .done() 来解决这个问题，但是遇到了无法检查计数器是否为 0 的问题，因为 .done() 需要一个函数，而 .done(如果) 不起作用。顺便说一句，我更像是一个 C++、java、C# 的家伙，并且对 jQuery、JS 和其他东西不太熟悉，如果我的错误是微不足道的，那么抱歉。 这是代码，你可以忽略这些长的 SQL 语句，我知道，它们不符合编码约定，但它们有效：

$("#btn-ins-patient").on("click", function() {
        ipcRenderer.once('insert-patient', function(event, arg) {
                        
            let checksql = "select count(*) as 'zaehl' from patient where "
            + "owner = " + arg.owner + " and name = '" + arg.name + "' and species = '" + arg.species + "' and breed = '" + arg.breed + "' and sex = '" + arg.sex + "' and neutered = '" + arg.neutered + "' and dead = '" + arg.dead + "' and chipnr = '" + arg.chipnr + "' and birthdate = '" + arg.birthdate + "'  and color = '" + arg.color + "';"

            db.all(checksql, function(error, rows) {
                if (error) {
                    console.log(error.code, checksql)
                    insertpatsql = "select * from patient where id = 1;";
                }
                else{
                    console.log(checksql);                      //second output in console, prints the right statement
                    for (let i = 0; i < rows.length; i++) {
                        var counter = rows[i].zaehl;
                        console.log(counter);                   //third output in console, prints 0
                        setCount(counter);
                        console.log(cnter);                     //fourth output in console, prints 0 again
                    }
                    if(cnter != 0){
                        insertpatsql = "select * from patient where id = 1;";
                        console.log(insertpatsql);
                        console.log("double entry was stopped");
                    }
                    else{
                        
                        console.log(insertpatsql);              // fifth output in console prints the right statement (insert)

                    }
                    
                }  
            });

            let insertpatsql = "insert into patient"
            + "(owner, name, species, breed, sex, neutered, dead, chipnr, birthdate, color, notes, diverse)"
            + "values ('" + arg.owner + "', '" + arg.name + "', '" + arg.species + "', '" + arg.breed + "', '" + arg.sex + "', '" + arg.neutered + "', '" + arg.dead + "', '" + arg.chipnr + "', '" + arg.birthdate + "', '" + arg.color + "', '" + arg.notes + "', '" + arg.diverse + "');";

            if(cnter == 0){
                db.all(insertpatsql, function(error) {
                    if (error) {
                        console.log(error.code, insertpatsql)
                    }
                    else{
                        console.log(insertpatsql);
                        loadPatients();
                    }
                });
            }
            else{
                console.log("double entry was tried", insertpatsql, cnter);
                                                              //first output in console, cnter is undefined
            }
        })

        let child = new BrowserWindow({
            height: 485,
            width: 795,
            parent: parent,
            modal: true,
            resizable: false,
            show: false,
            webPreferences: {
                nodeIntegration: true
            }
        })

        child.loadFile('./ins/patient.html')

        child.once('ready-to-show', () => {
            child.show()
        })

        child.on('closed', () => {
            child = null
        })
    })

select * from patient where id = 1; 只是出于安全原因，因为有时会执行第二个 db.all()，即使它不应该执行。我知道我的代码很乱，对不起，我整天都在努力解决这个问题......

这就是我设置 cnter（全局变量）的方式：

var cnter;

function setCount(cnt){
    cnter = cnt;
}

如何确保 checksql 及其代码块在插入之前执行？

Answer 1

好的，我想我解决了这个问题，将第二个块放在第一个块中。这是现在的代码：

$("#btn-ins-patient").on("click", function() {
        ipcRenderer.once('insert-patient', function(event, arg) {
                        
            let checksql = "select count(*) as 'zaehl' from patient where "
            + "owner = " + arg.owner + " and name = '" + arg.name + "' and species = '" + arg.species + "' and breed = '" + arg.breed + "' and sex = '" + arg.sex + "' and neutered = '" + arg.neutered + "' and dead = '" + arg.dead + "' and chipnr = '" + arg.chipnr + "' and birthdate = '" + arg.birthdate + "'  and color = '" + arg.color + "';"

            let insertpatsql = "insert into patient"
            + "(owner, name, species, breed, sex, neutered, dead, chipnr, birthdate, color, notes, diverse)"
            + "values ('" + arg.owner + "', '" + arg.name + "', '" + arg.species + "', '" + arg.breed + "', '" + arg.sex + "', '" + arg.neutered + "', '" + arg.dead + "', '" + arg.chipnr + "', '" + arg.birthdate + "', '" + arg.color + "', '" + arg.notes + "', '" + arg.diverse + "');";


            db.all(checksql, function(error, rows) {
                if (error) {
                    console.log(error.code, checksql)
                    insertpatsql = "select * from patient where id = 1;";
                }
                else{
                    console.log(checksql); //first output in console
                    for (let i = 0; i < rows.length; i++) {
                        var counter = rows[i].zaehl;
                        console.log(counter); //second output in console
                        setCount(counter);
                        console.log(cnter); //third output in console
                    }
                    if(cnter != 0){
                        insertpatsql = "select * from patient where id = 1;";
                        console.log(insertpatsql);
                        console.log("double entry was stopped");
                    }
                    else{
                        
                        if(cnter == 0){
                            db.all(insertpatsql, function(error) {
                                if (error) {
                                    console.log(error.code, insertpatsql)
                                }
                                else{
                                    console.log(insertpatsql);
                                    loadPatients();
                                }
                            });
                        }
                        else{
                            console.log("double entry was tried", insertpatsql, cnter); //fourth output in console, cnter is undefinded
                        }

                    }
                    
                }  
            });
            
        })
})

我不知道它是否真的有效，直到 ipcRenderer 尝试再次触发两次。一旦我确认它有效，我会标记它。

Answer 2

我不明白！！，但这是链接数据库事务的架构

function onSomeButtonClick()
{
  // The first query callback
  var firstQueryResults;
  var firstQuery = function(tx) {
    tx.executeSql(
      'SELECT * FROM databaseName WHERE greeting = "hello world"',
      [],
      function(tx, results) {
        firstQueryResults = results;
        return nextQuery(tx);
      });
  };

  var nextQuery = function(tx) {
    // Prepare something using firstQueryResults
    tx.executeSql('SOMETHING ELSE HERE',
      [],
      function(tx, results) {
        // Something good happens here
        return true; // Be sure to return false to roll back
      });
  };

  database.transaction(firstQuery, null, nextTransaction);
}

function nextTransaction() {
  // The next full transaction that's dependent on the
  // first transaction's data is called AFTER the first
  // transaction has completed.
}

Answer 3

我怀疑问题在于您在事件处理程序中注册了一个事件处理程序。在大多数情况下，事件处理程序应该在全局范围内注册一次，而不是在另一个事件处理程序中。

我不了解您使用该计数器所做的所有事情，但我认为您正在尝试这样做：

ipcRenderer.on('insert-patient', function(event, arg) {
                
    let insertpatsql = "insert into patient"
    + "(owner, name, species, breed, sex, neutered, dead, chipnr, birthdate, color, notes, diverse)"
    + "values ('" + arg.owner + "', '" + arg.name + "', '" + arg.species + "', '" + arg.breed + "', '" + arg.sex + "', '" + arg.neutered + "', '" + arg.dead + "', '" + arg.chipnr + "', '" + arg.birthdate + "', '" + arg.color + "', '" + arg.notes + "', '" + arg.diverse + "');";

    db.all(insertpatsql, function(error) {
        if (error) {
            console.log(error.code, insertpatsql)
        }
        else{
            console.log(insertpatsql);
            loadPatients();
        }
    });
})

$("#btn-ins-patient").on("click", function() {

    let child = new BrowserWindow({
        height: 485,
        width: 795,
        parent: parent,
        modal: true,
        resizable: false,
        show: false,
        webPreferences: {
            nodeIntegration: true
        }
    })

    child.loadFile('./ins/patient.html')

    child.once('ready-to-show', () => {
        child.show()
    })

    child.on('closed', () => {
        child = null
    })
})