尝试从函数返回一个流缓冲区

Question

我试图创建一个包含csv文件的zip文件，并从函数返回它作为缓冲区。我的代码如下:

const archiver = require('archiver');
const streamBuffers = require("stream-buffers");
createZipFromCsv(csv) {
var myWritableStreamBuffer = new streamBuffers.WritableStreamBuffer({
initialSize: (100 * 1024),   // start at 100 kilobytes.
incrementAmount: (10 * 1024) // grow by 10 kilobytes each time buffer overflows.
});
myWritableStreamBuffer.on('finish', () => {
console.log(myWritableStreamBuffer.getContents())
return Promise.resolve(myWritableStreamBuffer.getContents());
});
const archive = archiver('zip');
archive.pipe(myWritableStreamBuffer);
archive.append(csv, { name: 'csvName.csv' });
archive.finalize();
}

和函数调用:

const buffer = await createZipFromCsv("some,csv,data");
console.log(buffer)

但是，函数调用后的缓冲区控制台日志是未定义的。onfinish中的控制台日志返回一个良好的缓冲区，但仅在函数调用后的控制台日志之后。我很困惑为什么函数在缓冲区完成写入之前返回。

感谢任何帮助!

Answer 1

您需要将代码包装在一个返回的承诺中，然后适当地解析/拒绝。这里有一种方法:

const archiver = require('archiver');
const streamBuffers = require("stream-buffers");
createZipFromCsv(csv) {
return new Promise((resolve, reject) => {
const myWritableStreamBuffer = new streamBuffers.WritableStreamBuffer({
initialSize: (100 * 1024), // start at 100 kilobytes.
incrementAmount: (10 * 1024) // grow by 10 kilobytes each time buffer overflows.
});
myWritableStreamBuffer.on('finish', () => {
resolve(myWritableStreamBuffer.getContents());
});
myWritableStreamBuffer.on('error', reject);
const archive = archiver('zip');
archive.pipe(myWritableStreamBuffer);
archive.append(csv, { name: 'csvName.csv' });
archive.finalize();
});
}