Did you get ‘RuntimeError: can’t add a new key into hash during iteration‘ error? In this post we will check together a common pattern and how to solve it easily. The error message is self descriptive, we can’t update a hash during iteration and it can be reproduced with the following snippet: So here is a quick question, what will…
Easy approach to format Dates in Rails projects
I saw a lot of projects where the default date format was used. In fact, customizing the date format to provide a human-readable date will be very welcomed from your customers! So what should we do to start making our application awesome? No worries, it’s a very easy process that we will discover together. Example To get started we will…
ActiveRecord exists? and blank? under the hood.
When should I use exists? or blank? to check records existence? Does this choice has an impact on our application? Asking those questions is a good sign of curiosity! So we will see together how those methods work under the hood and without a long introduction let’s unpack ActiveRecord and dive deep into the source code. Putting exists? under the scope:…
Drop a table in production
In this post, we will see an approach how to safely drop a table from a production application without running into weird issues. As an example, we will use a simple blog that allows adding comments to each post and also has a simple stats table where it tracks likes, views, and shares of posts. The model diagram for this example is…
Rename an ActiveRecord model
Choosing a good name for a class or a variable isn’t easy at all and sometimes there is a requirement to rename existing tables and models to match the updated product audience. So how we should do this migration then: 1- Ask why The first step is to ask why should we rename the model, with a productive mindset and…
Best tip for junior developers
Let me share this short story about Bob and the wise man There was a small village where people care about the development of young generation and giving challenges to young kids was part of their culture. Bob was excited to get his first challenge, he was asked to cut down an old tree. He went early the next morning…
Add DB uniqueness constraint across tables
We saw previously in this post how to add uniqueness database constraint for a single table. But in real-world applications, we have different associations between models, so let’s start with an example: We have a service platform where a user can buy subscriptions for different services, the requirements are the following: A user can have many subscriptions for different services…
Write unique validation with confidence!
It’s easy to use model validation in Rails application and in this article, we will study some aspects with the uniqueness validator. So let’s start with an easy requirement, we want to have an Account model with a unique email attribute.
1 2 3 4 5 | class Account < ApplicationRecord validates :email, uniqueness: true end |
This solution works but it’s not enough. For beginners, it’s important to understand how validation work in Rails.…
Fix missing environment variables for production
It’s common to forget setting a new environment variable after deployment, so I’ll share a strategy that I’m using: 1- Use fetch method Let’s start with this example of missing NEW_KEY value:
1 2 3 | ENV["NEW_KEY"] # nil ENV.fetch("NEW_KEY") # KeyError: key not found: "NEW_KEY" |
So how this works? ENV is a hash-like accessor for environment variables so we can use hash methods but we need only fetch for the moment. Now…
Set multiline ENV variable in production
Did you try to set up a private key as ENV variable in production but you get the following error:
1 | OpenSSL::PKey::RSAError: Neither PUB key nor PRIV key: nested asn1 error |
So if you are setting your ENV variables through a terminal tool, use the following approach:
1 | MY_KEY=$(cat my_multiline_key.txt) |
Next, we need to remove the escape character added when setting the key:
1 | ENV.fetch("MY_KEY").gsub("\\n", "\n") |
That’s it we have fixed this error and…