無法從轉換流 nodejs 流式傳輸對象數組

Question

我正在嘗試讀取對象數組，將它們轉換並寫入 Nodejs 中的文件，它給了我錯誤““塊”參數必須是字符串類型或 Buffer 或 Uint8Array 的實例。收到對象的實例“

我的演示代碼：

const readStream = stream.Readable.from(res); // I create stream from array of objects
This is my custom transform stream:
var Transform = stream.Transform;

function Flatten(options) {
  Transform.call(this, options);
};
util.inherits(Flatten, Transform);
Flatten.prototype._transform = function (chunk, enc, cb) {
  
    let obj = chunk;
    let obj2;
    for (let j=0; j<obj.inner.length; j++) {
        let obj1 = obj.inner[j];
        obj2 = {...obj, ...obj1};
        
        delete obj2.inner;
        this.push(new Buffer(obj2));
    }
    
  cb();
};
Then I have a writable stream:
let writeStream = fs.createWriteStream('test1.txt');

Then I pipe all these await pipeline(readStream, tranf, writeStream);
that time I am getting the above error, tried using objectMode: true.

能否請你幫忙

Answer 1

首先，您需要添加一個選項來使用對象objectMode: true 。 然后不是將 Buffer 傳遞給this.push()而是使用JSON.stringify更改為字符串

const stream = require('stream');
const fs = require('fs');
const res = [{ inner: [1, 2, 3] }, { inner: [4, 5, 6] }, { inner: [7, 8, 9] }];
const Transform = stream.Transform;

class Flatten extends Transform {
    constructor(options) {
        super(options)
    }

    _transform(chunk, enc, cb) {
        let obj = chunk;
        let obj2;
        for (let j = 0; j < obj.inner.length; j++) {
            let obj1 = obj.inner[j];
            obj2 = { ...obj, ...obj1 };
            delete obj2.inner;
            this.push(JSON.stringify(obj2));
        }
        cb();
    };

};


const readStream = stream.Readable.from(res);
const writeStream = fs.createWriteStream('test1.txt');
const transform = new Flatten({ objectMode: true })

readStream.pipe(transform).pipe(writeStream);