LambdaDays 2017, FP concepts and their application

In my last post I tried to summarize the main concepts expressed by Prof. John Hughes and Prof. Mary Sheeran in their wonderful keynote at the LambdaDays 2017.

If you didn’t read it, well, here it is. Go on, I’ll be waiting for you here 😁


Jokes apart, at the end of my summary I left a little bit of suspense regarding the topics of my next (this) post but I also gave a few hints about them.

So, without further ado, here there are the two “mysterious concepts”:

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Previewing email in Rails with ActionMailer::Preview and Letter Opener

Developing email templates to be sent by our Rails application may sometimes be a long and tedious operation because under development you must continuously send to yourself the email in order to test the changes.

If you don’t want to waste your time, Rails provides a very helpful tool for those who need to build the layout for the emails of our application: ActionMailer::Preview. In fact, with this tool (available from Rails 4.1), you are able to generate the Rails mailer view without the need to actually send the email.
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LambdaDays 2017 – more than one month later…

I know, I should have written this article a while ago but I couldn’t find the time…sorry 😞

Anyway…one month…how time flies!

Last February, thanks to 😘 Mikamai, I had the immense pleasure to attend to an astonishing conf.

For the ones who don’t know, LambdaDays is an international 2 days conference that has been held in Krakow for four years now.

Its main focus is the “umbrella topic” of “Functional Programming”.

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Caching images in UICollectionView

In an iPad application we recently developed, we had several UICollectionViews loading many images that could be resized. Like the camera roll in the system app, we had a Grid layout with hundreds of image thumbnails that could go fullscreen if tapped.

During QA, we had performance issues: the memory footprint increased every time we entered in a UICollectionView and we loaded the images grid with hundred of images. The increase was a steady 21MB every time we entered and no memory was being release at any time.

At iOS’s whim, the application received a Memory warning and, unable to deal with the memory pressure, it crashed.

Always trying to avoid premature optimisation, now was indeed the time to sharpen our performance skills!

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How to share Rails i18n messages with React through webpack

This time I’m here for sharing a solution for a specific problem I encountered a couple of days ago.

There’s this existing Rails monolithic application. Team and customer decided that time had come for this app to be decoupled in two components: Rails would do its usual work as an administration and API backend, while React would be used for the frontend component. Everything related to the frontend would then be rewritten, keeping the same behaviour and visual design. But there are a lot of translations related to the user experience and that have now to be included in the javascript bundle, while they were before used by the server.
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Find if a list is circular with memory constraint

Usually developers when thinking about a solution put their focus on the complexity of the algorithm (O(n), O(n^2) …) rather than the memory consumption, so lets see an example where the constraint is the memory S.
I would like to share the solution to an interesting exercise that I was asked to solve during a technical interview.

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