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Growing Up

Until a few months ago, I never really was interested in my age, or the age of people around me. When someone asked me my age, I would have to pause and think about what year it was (a number I often forget) and calculate the years. Being born in 1990, it wasn’t too hard. Just add 10 to the last two numbers of the current year. My birthday is in November, so if it was currently before November, I’d just minus one.

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Elixir anonymous function shorthand

Elixir’s Getting Started guides go over the &Module.function/arity and &(...) anonymous function shorthand, but there are a couple neat tricks that are not immediately apparent about this shorthand.

For example, you can do something like &"...".

iex> hello_fun = &"Hello, #{&1}"
iex> hello_fun.("Keita")
"Hello, Keita"

Let’s have some more fun.

iex> fun = &~r/hello #{&1}/
iex> fun.("world")
~r/hello world/

iex> fun = &~w(hello #{&1})
iex> fun.("world")
["hello", "world"]
iex> fun.("world moon mars")
["hello", "world", "moon", "mars"]

iex> fun = &if(&1, do: "ok", else: "not ok")
iex> fun.(true)
"ok"
iex> fun.(false)
"not ok"

You can even use defmodule to create an anonymous function that defines a new module.

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Elixir: A year (and a few months) in

In the beginning of 2015, I wrote a blog post about how my then-current programming language of choice (Ruby) was showing itself to not be as future-proof as I would have liked it to be.

A lot has changed since then, but a lot has remained the same.

First: I have started a few open-source Elixir projects:

  • Exfile -- a file upload handling, persistence, and processing library. Extracted from an image upload service I’m working on (also in Elixir).
  • multistream-downloader -- a quick tool to monitor and download HTTP-based live streams.
  • runroller -- a redirect “unroller” API, see the blog post about it.

The initial push to get me in to Elixir was indeed its performance, but that’s not what kept me. At the same time, I also tried learning Go and more recently, Rust has caught my attention.

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tokyo.ex #1

I attended my first Elixir-related meetup yesterday, tokyo.ex #1.

(If the slides don’t work here, I have also uploaded them to YouTube.)

In my 5-minute lightning talk, I talked about the basics of using Exfile. Exfile is a file upload persistence and processing library for Elixir with integrations for Ecto and Phoenix.

Playing around with AWS Certificate Manager

I’m a big Let’s Encrypt fan. They provide free SSL certificates for your web servers so you can protect the traffic from prying eyes. In fact, the connection between your web browser and my blog server is made private thanks to Let’s Encrypt.

Using Let’s Encrypt requires some setup and automation on your part if you want to use it in the AWS cloud, but AWS recently launched something called the AWS Certificate Manager or “ACM”. ACM takes care of issuing, renewing, and provisioning certificates for you – which is great because uploading SSL certificates to CloudFront and Elastic Load Balancers is not the most fun thing to do. I would pay for this, but Amazon has decided to give it to everyone for free. :-)

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JavaScript Unit Tests in a Phoenix Application

There’s a guide to writing browser acceptance tests for Phoenix. Acceptance tests are nice, but sometimes you want to have unit tests. This is very easy to do with your Elixir code, but what about your JavaScript code that lives inside your Phoenix application?

I couldn’t find a good guide on this, so I’ll go over what I have set up for one of my latest Phoenix projects.

Setup

First, install mocha if you haven’t already. I’ll be using mocha, but you can use whatever test runner you want to. You’ll also need babel-register -- this will allow you to use Babel while the tests are being run in Node.

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Elixir's StringIO may not be what you think it is

In Ruby, there is a very handy class called StringIO. Basically, it allows you to treat a string like you would an IO object, such as an open file, etc. Very useful for in-memory “files” that you may not want to write to a temporary file.

In Elixir, there is a module called StringIO in the standard library. At first glance, these seem pretty similar:

Ruby:

Pseudo I/O on String object.

Elixir:

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Brutal Simplicity

My favorite pizza is the pizza Margherita. Any pizzeria I go to, I will order the Margherita first.

Why? It’s brutally simple. Four ingredients: dough, tomato sauce, mozzarella cheese, basil.

I wish more websites and applications would be like a good Margherita.

Simple.

Delicious.

????

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Homebrew and PostgreSQL 9.5 (or 9.6)

Edit Sept. 30 2016: PostgreSQL 9.6 was released today, and these instructions should work – just replace 9.4 with 9.5 and 9.5 with 9.6. I also have a guide using pg_upgradecluster on Ubuntu.

PostgreSQL 9.5 was released on Jan. 7, with lots of exciting new features.

I wrote a post about upgrading from 9.3 to 9.4 in the past, and many people found it useful, so I decided to update it a bit for the 9.4 to 9.5 upgrade.

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Elixir Pattern Matching in Anonymous Funs

filter_zed_by = "1"
list = [
  %{"a" => "1", "b" => "2"},
  %{"a" => "1", "b" => "5"},
  %{"a" => "2", "b" => "5"},
  %{"z" => "1", "x" => "2"}
]
Enum.filter list, fn
  %{"z" => ^filter_zed_by} -> true
  _ -> false
end

# => [%{"z" => "1", "x" => "2"}]
  • case in a fun is usually redundant
  • if is even worse
  • keep it simple

Hosting a Single-Page App on S3, with proper URLs

Note (2019/07/05): I’ve posted a follow-up to this post about limitations about the technique used here, especially when hosting an API on the same domain.

Amazon S3 is a great place to store static files. You might want to even serve a single-page application (SPA) written in JavaScript there.

When you’re writing a single-page app, there are a couple ways to handle URLs:

A) http://example.com/#!/path/of/resource
B) http://example.com/path/of/resource

A is easy to serve from S3. The server only sees the http://example.com/ part, and so it serves that file to everyone.

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