added new post about phoenix and array params

_drafts/til-arrays-elixir.md

@@ -1 +0,0 @@
-some_url?param[]=value1&param[]=value2

_posts/2020-04-10-til-4.md

@@ -0,0 +1,31 @@
+---
+post_title: 'Today I Learned #4: Passing array/list parameters to Phoenix controller'
+author: dreat
+layout: post
+published: true
+post_date: 2020-04-10 20:00:00
+tags: [til, elixir, phoenix]
+categories: [til, new_blog]
+---
+
+Hello!
+
+I had curious _incident_ while working. I was to investigate why our API won't work when passed array as url parameter for GET request.
+
+So, I peeked into the tests and we had test for it. I logged the incoming parameters and Phoenix got an array and worked with it perfectly. So I decided to grab the big guns. Enter curl.
+
+It was quite funny. My first insting was to create url like this: `some.url?param=[value1,value2]` but it didn't work. Phoenix read this as
+
+```elixir
+%{"param" => "[value1,value2]"}
+```
+
+and no combination of quotes would make this work.
+
+To skip some other things I tried - the thing you need to do is to use this
+
+```
+some_url?param[]=value1&param[]=value2
+```
+
+Phoenix will read all those values as elements of an array (or, in Elixir's context, a list) and it will work as intended.