PIPES.md

Javascrtipt Pipes

The k2 Tools Utilitis offer two types of pipe implementation

Both pipe implmentations function in broadly similar ways.

They are created by passing a consumer function to the pipe constructor functions available through @k2_tools/utils

Calling the pipe constructor creates an object which functions as a pipe.

The pipe object offers an accept method. Any item submitted to the accept method of the pipe is passed to the pipes consumer.

Pipes offer a mechanism to pass data from one component to another without each component havbing to be aware of the existence of the other.

Install

npm install @k2_tools/utils

Import

import {pipes} from "@k2_tools/utils";

Usage

K2_tools pipes utilities offers two pipe implementations

1. pipe
2. cachingPipe

Pipe

The basic pipe implementation provides a pipe which passes accepted items to the consumer used to contruct the pipe.

Constructing A Pipe

const consumer = (item) => {
  // ...
  // Do something with each tiem subnmitted to the accept method of the pipe
  // ...
  console.log(JSON.stringify(item);
};  // Define an item consumer function

const pipe = pipes.pipe(consumer); // Create a pipe using the defined consumer

Pipes can be costructed without a consumer. However, baisc pipes will throw an error if at item is submitted to the accept method of the pipe if it does not have a consumer to process the item accepted onto the pipe.

const pipe = pipes.pipe(); // Create a pipe without a consumer

Setting The Consumer Of An Existing Pipe

After a pipe has been constructed the setConsumer method of the pipe can be used to set the consumer function of the pipe.

const pipe = pipes.pipe(); // Create a pipe without a consumer

const consumer = (item) => {
  // ...
  // Do something with each item subnmitted to the accept method of the pipe
  // ...
  console.log(JSON.stringify(item);
}; // Create a consumer function to handle items submitted to the pipe

pipe.setConsumer(consumer);

A pipe may only have a single consumer. Calling setConsumer on a pipe which already has a consuemr will replace the consumer on the pipe and subsequent items accepted onto the pipe will be prossessed only by the most recnetly set consumer function.

Submitting An Item Onto The Pipe

Pipes can accept any variable and will pass the accepted variable to the configured consumer. If the pipe was not constructed with a consumer or the consumer has been removed by calling pipe.setConsumer(undefined); then a TypeError is thrown when an item is accepted onto the pipe.

pipe.accept({id: 123, type: "something", message: "An item"}); // Submit an item to the pipe.

Items submitted to the accept method of the pipe are immidiately passed to the consumer function to be consumed.

Caching Pipe

The Cahcing Pipe implementation differs from the basic pipe implamenetation above by caching items accepted onto the pipe while the pipe does not have a consumer.

Constructing A Caching Pipe

const consumer = (item) => {
  // ...
  // Do something with each tiem subnmitted to the accept method of the pipe
  // ...
  console.log(JSON.stringify(item);
};  // Define an item consumer function

const pipe = pipes.cachingPipe(consumer); // Create a caching pipe using the defined consumer

Caching Pipes can be costructed without a consumer. Items submitted to the accept method of the caching pipe are cached while the pipe does not have a doncumer defined. As soon a a consumer is added to the pipe the cached items are submitted to the consumer in the order they were submitted to the accept methof of the pipe.

const pipe = pipes.cachingPipe(); // Create a caching pipe without a consumer

Setting The Consumer Of An Existing Caqching Pipe

After a pipe has been constructed the setConsumer method of the pipe can be used to set the consumer function of the pipe.

const pipe = pipes.cachingPipe(); // Create a caching pipe without a consumer

const consumer = (item) => {
  // ...
  // Do something with each item subnmitted to the accept method of the pipe
  // ...
  console.log(JSON.stringify(item);
}; // Create a consumer function to handle items submitted to the pipe

pipe.setConsumer(consumer);

A pipe may only have a single consumer. Calling setConsumer on a pipe which already has a consuemr will replace the consumer on the pipe and subsequent items accepted onto the pipe will be prossessed only by the most recnetly set consumer function.

Submitting An Item Onto The Caching Pipe

Pipes can accept any variable and will pass the accepted variable to the configured consumer. If the pipe was not constructed with a consumer or the consumer has been removed by calling pipe.setConsumer(undefined); then a the accepted items are cached until a consumer is set for the caching pipe.

pipe.accept({id: 123, type: "something", message: "An item"}); // Submit an item to the pipe.