processing-pipe

About this module

This is another module aiming at making asynchronous code more readable and easy to use. Its main purpose is to enable you to construct a chain of (asynchronous) function calls and invoke it afterwards via a simple API. The code is well tested and therefore expected to be ready for production.

Installation

npm i processing-pipe --save

API

Signature of 'chain'-function

function chainable(next, data, as, much, further, variables, as, you, like) {
  next(hand, over, all, variables, you, need);
}  

Actually just next is needed - it will be given the generated %Bindeglied% function that will do the work of correct invocation of the next chain item for you. It has to be once in your code or the chain will break. It shouldn't be called more than once. this is set to a context variable provided by the library to enable access to methods like abort(). If you need this to point to instance a method is bound to you might wrap the function with another function. Using bind() will also work. If the first parameter given to it is an instance of Error processing will be aborted the same way this.abort() (further down this document) would do it.

Construct new instance

var Pipe = require("processing-pipe");
var p = new Pipe();

Add chainable element

var chainableFunction = function (next, data) {
  //Process data
  next(data);
};
 
p.place(chainableFunction); //Places the given element at the end of the pipe
p.placeLast(chainableFunction); //This is just an alias for place()
p.placeFirst(chainableFunction); //Places the given item at the beginning of the pipeline

The methods place(), placeLast() and placeFirst() might be used for adding elements to any Pipe instance.

Start processing

p.flood(data, function (err, data, ctx) {});

The first parameter given to flood() will be handed over as the 2nd parameters to the first element in the chain. The second parameter might contain the final callback function which gets invoked after...:

• ... the chain successfully completed
• ... an error occurred and gets handled via next(error)
• ... processing gets aborted via this.abort(). ctx refers to the object which is bound to the chainable function as this. ctx.piecesPassed contains the number of successfully passed chain-items. sctx.aborted gives information (boolean) whether the chain has been successfully completed or aborted (due to abort() or an error).

Error handling and aborting

Processing might be aborted by calling this.abort() inside chain function. In case this is not reachable or an error occured one can call done with an instance of Error as first parameter. In both cases ctx.aborted (which can be accessed in onDone handler) is set to true.

License

The MIT License (MIT)

Copyright (c) 2015 Florian Loch

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.