middleware 1.2.1

# Middleware for Python

**Copyright (c) 2016 David Betz**

## Installation

pip install middleware

[](https://travis-ci.org/davidbetz/middleware)
[](https://badge.fury.io/py/middleware)

## Compatibility

Python 2 and 3

## Purpose

Most everyone needs a concept of middleware.

Following are examples of using this, see ```test_middleware.py``` for full examples.

class AdditionMiddleware1(Middleware):
def create(self):
def func(mwa, context):
try:
counter = context['counter']
except:
counter = 0
context['counter'] = counter + 1

return next(mwa)

return func

When using a class, add a ```create``` function which returns a function. This inner fuction accepts the middleware array and the data context and returns ```next(mwa)``` to create a middleware chain.

For this example, I'll add two more:

class AdditionMiddleware2(AdditionMiddleware1):
pass


class AdditionMiddleware3(AdditionMiddleware2):
pass

Now to run it. Use ```set``` to set an array of middleware and ```add``` to add one to the array. ```set``` overwrites everything. That's just what ```set``` means.

handler = Handler()
handler.set([AdditionMiddleware1, AdditionMiddleware2])
handler.add(AdditionMiddleware3)
handler.execute()

# handler['counter'] == 3

In this case, there is no initial context and each of the three middleware increment a counter ending with ```handler['counter'] == 3```.

You can skip the entire class stuff too:

handler = Handler()
def inline(wma, context):
context['myvalue'] = 12
handler.add(inline)
handler.execute()
# handler['myvalue'] == 12

Use the following to send initial context:

handler = Handler(counter=1)

It's actually ```kwargs```, so you can load it up:

handler = Handler(**{'a': 1, 'b': 2})
def inline(wma, context):
context['a'] = context['a'] + context['b']
handler.add(inline)
handler.execute()