com.stuartsierra/component & ring/compojure example

[JPatrick Davenport]

Hello,
I'm trying to create a web app. I'm having the damnest time trying to figure out how to layer my application. I want to pass protocol implementations to the routes. The protocols define interacting with various data sources that I need down the way.

I saw Stuart Sierra's talk about Component. It looks to satisfy my needs. What I can't find is an example project for component and compojure. Unfortunately the project com.stuartsierra/component is poorly named. Googling for component + compojure brings back mostly false positives.

Does anyone have a gist or blog post about how to do this?

Thanks,
JPD

[gaz jones]

Here is a toy app that downloads nzbs from usenet:

https://github.com/gar3thjon3s/leacher

It's not documented, but it works. The component stuff is hooked up here:

https://github.com/gar3thjon3s/leacher/blob/master/src/clj/leacher/main.clj#L53

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[Daniel Szmulewicz]

You may want to look here for integrating components in your app. 

https://github.com/danielsz/system/

[Andrew Meredith]

This is not a full example, but I ran into the same issue when building an app for the Clojure Cup not too long ago. The general approach I used is this:

• create the Compojure routes in a function with the components I need as parameters
• declare the web server itself (I used httpkit) as a component with the dependencies needed for the routes
  
• build a handler from the routes within the web server component's start function, passing the dependencies into the route-generating function

I'm no Clojure expert, and this was my first project using Stuart Sierra's Component library, so I would be interested to hear some feedback from the more seasoned Clojure folks here.

Here is the relevant file from my project if you are interested: https://github.com/kendru/tourbillon/blob/master/src/tourbillon/www/core.clj#L67

[Daniel Szmulewicz]

1, Extract the app out of the Webserver record into its own var. 
2, Add to the Webserver record an additional argument called handler. 

2, Put the component in a separate namespace. 

3, Initialize your component with the app var. 

OR, use system, which does all of the above for you. https://github.com/danielsz/system/

I'll post an example application in the repo if people are interested.  

[Daniel Szmulewicz]

I posted a working example in the system repo: 

https://github.com/danielsz/system/tree/master/example

On Tuesday, October 7, 2014 2:33:33 PM UTC+3, JPatrick Davenport wrote:

[Juho Teperi]

The Stuart Sierra's talk about Component has short bit about using it with ring, at around 32:24.

Idea is that you'll wrap your basic routes with a middleware which will assoc components to every request.

Difference to the other approach (creating the routes using fn taking the components as params) is that you are referencing the routes through a var so you can update your routes by evaluating the route definition again and you don't need to reset the system.

I have a example here: https://gist.github.com/Deraen/9d65f447593859dd07ae. It also has some compojure-api stuff to enable easier access to components for the handlers.

On Tuesday, October 7, 2014 2:33:33 PM UTC+3, JPatrick Davenport wrote:

[Huahai Yang]

This solution (creating the routes in a function and passing components into the function) seems to be the best solution. Other solutions all require defining the routes a prior, which may be the root of the problems, because some handlers may depend on functions generated by components in the run time.

-huahai