我试图异步获取某些pdf文件的内容。要做到这一点,我使用Promise.mapSeries
与request.getAsync
和蓝鸟spread
。
但在then
我需要直接使用request
和pipe
获得createWriteStream
的结果。就像是:
request(url).pipe(fs.createWriteStream(file));
这是代码,我正在使用:
const Promise = require('bluebird');
const request = Promise.promisifyAll(require('request'), { multiArgs: true });
const fs = Promise.promisifyAll(require("fs"));
const urls = ['http://localhost/test-pdf/one.pdf', 'http://localhost/test-pdf/two.pdf'];
Promise.mapSeries(urls, url => {
return request.getAsync({url: url, encoding:'binary'}).spread((response, body) => {
if (response.statusCode == 200){
let r = {};
r.name = url.match(/\/([^/]*)$/)[1]; // get the last part of url (file name)
r.content = body;
console.log(`Getting ${r.name}`);
return r;
}
else if (response.statusCode == 404){
console.log(`The archive ${url.match(/\/([^/]*)$/)[1]} does not exists`);
}
else throw new Error(`Unsuccessful attempt. Code: ${response.statusCode}`);
});
}).then((result) => {
// Here I want to 'pipe' to a file the result from 'getAsync'
}).catch((error) =>{
console.error(error);
})
我的问题:
如何使用getAsync
函数将pipe
的结果传递给文件?有可能的?
PD:我知道我可以使用fs.promises
,但只是想知道是否有可能以我发布的方式进行
我认为答案已经在问题中,.then()
似乎是你寻求的.pipe()
。
可能缺少的是(result)
应该是(results)
,即。由{name, content}
引起的所有Promise.mapSeries(urls, ...)
对的数组。
Promise.mapSeries(urls, url => {
return request.getAsync({'url':url, 'encoding':'binary'}).spread((response, body) => {
if (response.statusCode == 200) {
return {
'name': url.match(/\/([^/]*)$/)[1], // get the last part of url (file name)
'content': body
};
} else if (response.statusCode == 404) {
throw new Error(`The archive ${url.match(/\/([^/]*)$/)[1]} does not exist`);
} else {
throw new Error(`Unsuccessful attempt. Code: ${response.statusCode}`);
}
});
}).then((results) => {
// Here write each `result.content` to file.
}).catch((error) => {
console.error(error);
});
在实践中,您可能不会选择以这种方式编写它,因为在任何写入开始之前,每个getAsync()
都需要完成。
在大多数情况下(可能是你想要的那种情况)更好的流量将是每个成功的getAsync()
的内容尽快写入:
Promise.mapSeries(urls, url => {
let name = url.match(/\/([^/]*)$/)[1]; // get the last part of url (file name)
return request.getAsync({'url':url, 'encoding':'binary'}).spread((response, body) => {
if (response.statusCode == 200) {
// write `body.content` to file.
} else if (response.statusCode == 404) {
throw new Error(`The archive ${name} does not exist`);
} else {
throw new Error(`Unsuccessful attempt. Code: ${response.statusCode}`);
}
});
}).catch((error) => {
console.error(error);
});
更进一步,您可能会选择更好地处理错误,例如您可能希望:
这样的事情可能是:
Promise.mapSeries(urls, url => {
let name = url.match(/\/([^/]*)$/)[1] || ''; // get the last part of url (file name)
if(!name) {
throw new RangeError(`Error in input data for ${url}`);
}
return request.getAsync({'url':url, 'encoding':'binary'}).spread((response, body) => {
if (response.statusCode == 200) {
// write `body.content` to file.
return { name, 'content': body };
} else if (response.statusCode == 404) {
throw new Error(`The archive ${name} does not exist`);
} else {
throw new Error(`Unsuccessful attempt. Code: ${response.statusCode}`);
}
})
.catch(error => ({ name, error }));
}).then((results) => {
let successes = results.filter(res => !res.error).length;
let failures = results.filter(res => !!res.error).length;
let total = results.length;
console.log({ successes, failures, total }); // log success/failure stats
}).catch((error) => {
console.error(error); // just in case some otherwise uncaught error slips through
});