Question

我用node.js实现了以下代码，我想知道为什么调用writeToDB但是第一次没有在数据库中插入数据。

uploadInfoObject = {
    ProcessId: pid,
    Type: "type",
    ModifiedDate: new Date(),
    Status: "Started",
    Message: "Processing Started"
};
writeToDB(uploadInfoObject);
console.log('File Downloaded! ' + data.ContentType);
var exec = require('child_process').exec,
    child;
child = exec('gs -sDEVICE=jpeg -dTextAlphaBits=4 -r300 -o /tmp/%d.jpeg ' + stored_pdf, function(error, stdout, stderr) {
    uploadInfoObject = {
        ProcessId: Processid,
        Type: "Ticket",
        ModifiedDate: new Date(),
        Status: "Processing",
        Message: "Splitting into pages done"
    }
    writeToDB(uploadInfoObject); //this gets called  but data is not there in the db
});

writeToDB Funciton

function writeToDB(infoObject) {
    dbService.connectDb(config.DB_CONFIG.CONNECTIONSTRING, {})
    .then(() => {
        return dbService.insert(infoModel(dbService), infoObject);
    })
    .then(data => dbService.disconnectDb(data))
    .then(data => console.log("success"))
    .catch((error) => {
        dbService.disconnectDb(error).then(error => {
            console.log(error);
        })
    });
}

请帮忙

Answer 1

首先，从writeToDB返回一个Promise，然后将writeToDB(uploadInfoObject)之后的代码包装在.then中，就像这样

uploadInfoObject = {
    ProcessId: Processid,
    Type: "Ticket",
    ModifiedDate: new Date(),
    Status: "Started",
    Message: "Processing Started"
};
writeToDB(uploadInfoObject)
// wrap in .then
.then(() => {
    console.log('File Downloaded! ' + data.ContentType);
    var exec = require('child_process').exec;
    exec('gs -sDEVICE=jpeg -dTextAlphaBits=4 -r300 -o /tmp/%d.jpeg ' + stored_pdf, function(error, stdout, stderr) {
        uploadInfoObject = {
            ProcessId: Processid,
            Type: "Ticket",
            ModifiedDate: new Date(),
            Status: "Processing",
            Message: "Splitting into pages done"
        }
        writeToDB(uploadInfoObject); //this gets called  but data is not there in the db
    });
});
function writeToDB(infoObject) {
    // add return so a promise is returned
    return dbService.connectDb(config.DB_CONFIG.CONNECTIONSTRING, {})
    .then(() => dbService.insert(infoModel(dbService), infoObject))
    .then(data => dbService.disconnectDb(data))
    .then(data => console.log("success"))
    .catch((error) => {
        dbService.disconnectDb(error).then(() => {
            // throw the original error, otherwise .then will be called!
            throw error;
        })
    });
}

注意：你的writeToDB函数有一个缺陷，它捕获错误，但随后处理它 - 任何调用该函数的代码都将继续.then - 因此抛出断开连接。然后回调

writeToDB函数只执行一次

1 个答案: