Phoenix for Rails Developers – Part 2

I now have the code working upto the cart on the page.

Elixir and Phoenix are still great for showing exactly where the error is.

This can be handy as Elixir is very picky on whitespace usage.

Frequent use of:

mix clean

mix phx.routes

Will show any compiler warnings. It’s best to keep on top of these as they do give you clues as to obvious typos. This is especially true of unused variables.

It’s great that a whole chapter was written test first – especially when this demonstrates the DDD concept of Contexts. This is my main bugbear on some of the other Elixir books – tests have been removed to save space.

Also when you add a Plug you need to restart the server – these are not automatically added.

Phoenix for Rails Developers – Part 1

I was lucky enough to win a copy of Phoenix for Rails Developers.

(Thanks to @plataformatec)

This gives me one more thing to study!

Oddly I am not a Rails developer (but have worked on a number of frameworks that were inspired by Rails).

So far I am working through the main examples and will post them here:

I am developing this using Visual Studio Code.

Typically I also have two terminal tabs open.

The first is to run the application in:

mix phx.server


iex -S phx.server

The second is used for generator or to update git.

I am working with Elixir 1.6.4

So far the book is a gentle introduction to Phoenix. The language is introduced as needed.

It has stayed away from more complex Elixir topics (OTP).

When I have made typos the Elixir compiler will always tell you exactly where you have made the mistake, although it is not always obvious what the mistake was. The live reloading of the web application does allow for very rapid feedback. You do need to remember to restart the app on non-website changes.

The only catch that I have had so far is setting up Postgres locally. All other details have been clearly explained.

Introduction to React

This is a minimal introduction to React. These are intended to be rough notes for my future self. Any other use is entirely fortuitous.

I have taken the Pluralsight course:

This is based upon using the online repl found at:

// This is a simple function based react component.
// Note that the name of the component has to start with a capital.
// You need to treat the props as immutable.

const MyComponent = (props) => {
  return ( 
{props.greeting} {}
); }; // This is a simple class based React component // State is mutable, but you need to use the setState function // so that the UI will be re-rendered. // The state defined here is a proposed js extension that works through Babel. class App extends React.Component { state = {name: "Fred"}; render() { return (
); }; }; // This is the bootstrap that injects React into a page // Here mountNode is an id of a div ReactDOM.render(<App />, mountNode);


So from the above sample a quick comparison of React to AngularJs.

React is a view model that can be injected into a page. It follows functional programming idoms (props are immutable, state is updated by returning deltas that are merged into it). The html is embedded into the script so it does not require a distinct template language. It creates a virtual DOM that is dynamically updated when the data changes.

AngularJs is a full framework with routing, templating. It is typically added via custom tags. The developer needs to cede control of a region of a page to angular. Angular typically has distinct templates that are rendered.

They can be made to play well together – React can act as the View to an Angular application.

Operating a Kubernetes Application via 12 Factor Application

For the last few years I have been working on a suite of Heroku applications (previously Azure had similar functionality).

One of the beauty of these is the separation of config and build. This allows the only difference between environments (for secrets such as db connection strings or feature toggle environment variables) to be a versioned secure set of configuration. Importantly these configs can be changed without rebuilding the code.

Here is an article that discusses the capability of running kubernetes as a 12 factor application.