Rob Peck Observations on technology, leadership and life.

Incrementally Migrating from Apache to nginx

I am currently in the process of migrating a bunch of sites on this machine from Apache to nginx. Rather than take everything down and migrate it all at once, I wanted to do this incrementally. But that raises a question: how do you incrementally migrate site configs from one to the other on the same machine, since both servers will need to be running and listening on ports 80 and 443?

The solution I came up with was to move Apache to different ports (8080 and 4443) and to set the default nginx config to be a reverse proxy!

Just Take The Train

I love flying. Always have. Ever since my first flight as a kid, there was just something magical about getting into a giant metal bird and taking to the sky. I say was because it seems like, especially over the last decade or so, we have gone out of our way to make flying as miserable an experience as possible.

The “golden age” of air travel is long behind us and flying is now just a completely miserable experience. And it pains me to say that because I used to love flying. I loved airports, watching planes, feeling the potential of all the places you could go. But now, it is just an objectively awful experience.

Hierarchies: Finding Parents, Children and Descendents using Swift

It usually doesn’t take beginning macOS/iOS developers long to discover NotificationCenter and see it as the solution to every single problem of passing data around to different controllers. And NotificationCenter is great, but it has some downsides. Notably, it is very easy to introduce retain cycles (and memory leaks) unless you are very careful to track and free the listener when the object is released. This has bitten me on several occasions.

In general, excessive use of NotificationCenter ends up creating a difficult to maintain app where it is not entirely clear what is responding to what and where.

Creating Traits or Mixins in Swift

Object oriented programming is great, but sometimes things don’t fit neatly into a superclass/subclass hierarchy. You may have a piece of code that would be needed in several contexts, but for technical reasons beyond your control you cannot merge them into a single hierarchy.

Some languages have the concept of multiple inheritence, where a subclass can specifically inherit from several parents. But this has it’s own set of problems. Many other languages, however, solve this through the use of traits or mixins. These allow us to have a set of methods that are basically copied into the object at compile time. This way they can be used anywhere they are needed.

Swift doesn’t have the concept of mixins or traits per se. But, starting with Swift 3, you can get very equivalent functionality using protocol default implementations.

Debugging the Responder Chain in Swift

Somewhat related to my previous post about responder chains, sometimes it is useful to be able to debug what all is in the responder chain at any given time. As a good rule of thumb, all ancestor views of a view are in that view’s responder chain, as well as (usually) the related controllers.

The Responder Chain: Bubbling Events using NSResponder and UIResponder in Swift

The responder chain is one of those parts of macOS and iOS development that may seem a little strange if you have not done any GUI programming before. Briefly, a responder chain is a hierarichy of objects that can respond to events. So, for example, a click or a tap might be passed up the responder chain until something responds to the action.

But, the responder chain is more than just UI events. We can pass our own custom events up the responder chain as well!

Sequential Chained Requests with Siesta and Swift

Siesta is a framework for Swift that dramatically simplifies working with RESTful APIs. And like many things in Swift, it is natively built around asynchronous execution. It may fire any number of requests back, and they may complete in any order that is undefined.

But sometimes, you need to execute things in a specific order. Like when the result of one call will change subsequent calls. A classic example of this is an API where you might need to create a folder first, then upload files into the folder you created. So the folder creation needs to happen first, then the file uploads can happen after.

Recursive Queries with MySQL

Discovered something neat with the new version of MySQL and thought it warranted a mention. Storing tree structures in a relational database is a common use case across many different areas of tech. The problem comes when you need to construct a query based on a subset of that tree.

But MySQL 8 has some nice new features that makes doing this a breeze.