Question

我正在尝试合并多个文件（如果数据库结果返回带有非空'json'字段的多个元素，则创建PDF文档。）

现在合并只发生一次，并将第一个元素与element['json'] != ''合并在一起。

合并逻辑是：

除了我们将创建的

之外，所有PDF都已创建

如果元素包含某些JSON，则创建PDF

如果元素不包含JSON，请将其合并到以前的PDF

也许将所有承诺推送到数组并将它们传递给Promise.all（）会有帮助吗？真的卡住了。

app.get("/api/generatePDF", jsonParser, function(req, res) {

var saveFilename, savePath;
var idDocument, idPatient, idDoctor, idItem;
var orientation = "";
var url = req.route.path;
var tbl = "";
var html = "";
var hasTables = 0;
console.log(req.query.json);
var savedJSON = JSON.parse(req.query.json);
var flag = 4;
var id_inventory = parseInt(savedJSON['id_inventory']);
var request = new sql.Request();
var files = new Array();
var badFiles = new Array();
var options = "";
var mergeNeeded = parseInt(savedJSON['param']);
if (mergeNeeded == 1) {
    flag = 14;
}
var cnt = 0;
var output = parseInt(savedJSON['output']);
var mergedName = savedJSON['merged_name'];
var numRows = 0;
var idSpec = mergeNeeded;
if (id_inventory == 0) {
    var pid = savedJSON['id_patient'];
    var idDocType = savedJSON['id_doc_type'];
    idSpec = savedJSON['id_spec'];
    flag = 10;
    request.input('id_patient', sql.Int, pid);
    request.input('id_doc_type', sql.Int, idDocType);
}
request.input('id_spec', sql.Int, idSpec);
request.input('flag', sql.Int, flag);
request.input('redo', sql.Int, 1);
request.input('id_inventory', sql.Int, id_inventory);

request.execute("create_json").then(function(result) {
    var size = result.recordset.length;
    return Promise.all(result.recordset.map(function(element) {

            savePath = element['path'];
            idItem = element['id_item'];
            saveFilename = element['filename'];
            options = { "format": "A4", "orientation": element['orientation'], "renderDelay": "undefined", "border": "10mm" }
            idPatient = element['id_patient'];
            htmlFile = element['id_template'];
            var fillTemplate = new Promise((resolve, reject) => {
                files.push(basePath + element['path'] + separator + element['filename']);
                if (element['json'] != "") {
                    fs.readFile('templates' + separator + element['id_template'] + '.html', 'utf8', function(err, data) {
                        if (err) {
                            return console.log(err);
                            reject(err);
                        }
                        html = data;
                       // filling the template
                        resolve(html);
                    });
                }
            });
            var makeDirectory = new Promise((resolve, reject) => {
                if (element['json'] != "") {
                    mkdirp(basePath + element['path'], function(err) {
                        if (err) {
                            reject(err);
                        }
                        resolve(element);
                    });
                }
            });

            var makePDF = (html) => {
                return new Promise((resolve, reject) => {
                    if (element['json'] != "") {
                        pdf.create(html, options).toFile(basePath + element['path'] + separator + element['filename'], function(err, res) {
                            if (err) {
                                console.log(err);
                                reject(err);
                            } else {                                   
                                var request2 = new sql.Request();
                                request2.input('flag', sql.Int, 5);
                                request2.input('id_inventory', sql.Int, element['id_item']);
                                request2.execute("PDF_create_json", (err2, result2) => {});                                    
                            }

                            if (mergeNeeded == 1) {
                                if ((files.length > 100) || (files.length == size)) {
                                    PDFMerge(files, { output: basePath + mergedName }).then(() => {
                                        files.length = 0;
                                        files.push(basePath + mergedName);
                                        return "OK";
                                    })
                                }
                            } resolve("OK");
                        });
                    } else {

                        if (mergeNeeded == 1) {
                            if ((files.length > 100) || (files.length == size)) {
                                PDFMerge(files, { output: basePath + mergedName }).then(() => {
                                    files.length = 0;
                                    files.push(basePath + mergedName);
                                    return "OK";
                                })
                            }
                            console.log("mergedname: " + mergedName);
                            console.log("Files have been merged");
                            resolve("OK");
                        }
                    }

                });
            };
            return makeDirectory
                .then(() => {
                    return fillTemplate
                })
                .then(makePDF)
                .then(() => {
                    console.log(files);
                })
        }

    ))
}).then(results => {
    res.end("all done");
})

}）;

Answer 1

您需要观察控制流程。是的，你正在创造承诺但不等待它们完成。您可以使用async/await同步或像bluebird

这样的承诺库

您的特定代码段的根本问题是result.recordset.forEach(element => {，它基本上是同步运行，然后调用res.end()

您可以制作所有内容async/await，但您可能需要宣传request.execute("create_json", callback)电话。

或者您可以使用Promise库来执行类似

的操作

Promise.each(result.recordset, function returnAPromise(){
  // your stuff here. Make sure this returns a Promise (chain)
})
.then(results => { 
  // now call res.end() 
})

确保首先处理数组中的所有内容。（您还希望catch承诺链res.error()或任何呼叫，并确保您的Promise返回以便成功链接：

return makeDirectory.then(() => {
            return fillTemplate.then(result => {
                return makePDF(result).then(() => {
                     console.log("");
                });
            });
        });

或巩固

return makeDirectory
.then(() => {
   return fillTemplate
})
.then(makePDF)
.then(() => { console.log('here') } )

这些只是一个起点，但希望你觉得它有用。

node.js承诺在for循环中

1 个答案: