Streams in node

reference.md

• https://community.risingstack.com/the-definitive-guide-to-object-streams-in-node-js/

stream.md

stream error handling

var a
 .on('error', handleError)
 .pipe(b)
 .on('error', handleError)
 .pipe(c)
 .on('error', handleError);

reader

• pull
• push
• antingen subriscribe to the data event OR .resume()

reader.prototype._read = function(size) {
  this.push(23); // emits 'data'
  this.push(null); // emits 'end'
}
writer
 .write(str | buffer)
 .end

all data can be modelled as a stream (not just I/O)

transformStream._flush is called after reader calls 'end'

buildPage

var readFile = fs.createReadStream('./lib/base.html'),
    outfile = () ? : ,
    writeFile = fs.createWriteStream(outFile)

readFile
 .pipe(addPosts)
 .pipe(addPaginator)
 .pipe(writeFile)

transform
  ._transform = function(chunk, enc, cb)
    // add html - no push
    this._html += toHtml(chunk.toString())
  ._flush = function(cb)
    // add posts
    // add paginator

invisible NSA stream

transformer._transform = funciton(chunk, enc, cb) this._length += chunk.length; this.push(chunk); cb();

transformer._flush = function(cb) this.emit('length', this._length); cb();

---

weather_sample - example stream

• error handling seems difficult i.e forwarding errors
• http://stackoverflow.com/questions/21771220/error-handling-with-node-js-streams
• http://grokbase.com/t/gg/nodejs/12bwd4zm4x/should-stream-pipe-forward-errors
• see rowkaround by joelrich

req
  .pipe(request)
  .pipe(compileWeather)
  .on('error', next) // called by whom?
  .on('end', next) // called by compile..?