Cutting to the chase: rescue/1 and catch/1 (rescue and catch with one parameter) handle different types of errors; to handle all kinds of errors use catch/2 (the version of catch with two parameters) . See the GitHub README for complete examples, and there is additional information in the docs. Error…

Writing an assert_invalid macro for ExUnit assertions. Implementation at the bottom. I was working a lot with Ecto Changesets - using them for validation in my HTTP application. The application code (the code in my lib/ folder) was very nice, but I was not happy with the verbosity of the…

ETS will hold references to large binaries, even if just part of the original binary is stored in a table. Copy binaries if pieces of them are going to be kept around for a long time. I was creating a new Elixir application that was part of a larger micro…

# Add to shell profile export ERL_AFLAGS="-kernel shell_history enabled" The ERL_AFLAGS variable is for setting a list of options which are added to the beginning of the erl command. In this case, we are adding the shell_history option for saving our shell history between sessions. Note that “shell” here means…

The handle_continue/2 callback prevents race conditions and allows for faster, asynchronous initialization. Let’s start by looking at the problems that handle_continue solves. If you don’t care about the problems and just want the code, you can skip to the end or checkout (pun intended) the GitHub repo. Here is a…

Wrap your return values in tuples so you can clearly match them in the else block The with expression allows us to declare clauses and their expected results. The clauses are executed in order until the end of the list, or until one clause doesn’t match with its expected result…

Using inets and httpd to create a simple HTTP server without adding external dependencies Recently I needed to add a healthcheck endpoint to an application that was solely responsbile for reading and writing to Kafka. Normally when I am creating an HTTP application I would reach for Cowboy or Phoenix…

This is a post about how Elixir knows the difference between Erlang modules, Elixir modules, and Elixir atoms If you have ever come across Elixir code that calls an Erlang module, you will know it looks something like this: However, normal atoms that are declared in Elixir code don’t get…

Sometimes I come across code where an map (or tuple) is being tested against a pattern to return a boolean result; like this: That works fine, but can be simplified by using the Kernel.match?/2 function: Like when using other (more famous)Kernel functions such as ==/2, to_string/1, and send/2, the "Kernel" prefix can be omitted leaving us with a clean one-line statement. Here is a silly “real-world” example which shows that you can also use guard clauses in your match expression: