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Faking Flexbox with legacy techniques

Flexbox is great, but you don't get reliable support in Internet Explorer.

The attached article shows how to accomplish many Flexboxish effects without actually using flexbox statements.

Repeats

Do not use "flex: 1" or "flex-basis: 0" inside "flex-direction: column" when you need to support IE11

Flexbox is awesome. Most of it even works in IE11, but flex: 1 won't work reliably in Internet Explorer.
This it because implicitly sets flex-basis: 0 which IE fails to support properly.

Example

Consider the following HTML and CSS.

<div class="container">
  <div class="child">
    foo
  </div>
  <div class="bar">
    bar
  </div>
</div>
.container {
  display: flex;
  flex-direction: column;
}

.child {
  flex: 1;
}

See it in action at Plunker.

Background

Auto-destruct in 12 days

Updated: How to test your website for different versions of Internet Explorer or Edge

  • Updated link to Microsoft's VirtualBox images
  • Removed IETester method
  • Wrote about BrowserStack
Repeats

Hints for debugging MySQL InnoDB deadlocks

Deadlocks only occur if two transactions in separate threads compete for the same rows in the database. They usually (but not necessarily) only happen when trying to update or otherwise lock several rows in different order.

Solving deadlocks is potentially complicated, so here are a few pointers:

  • MySQL should always detect the deadlock right when it happens, and will throw an error to one of the offending threads. This error states the SQL statement that this thread was currently waiting for, and that tried to acquire one of the competin…

Minimal JavaScript function to detect version of Internet Explorer or Edge

If possible your code should detect features, not browsers. But sometimes you just need to sniff the browser. And when you do, you're probably fighting a Microsoft product.

The following function returns a Number like 10, 11, 12, 13 for Internet Explorer or Edge (anything above 11 is Edge). It returns undefined for any other browser.

```
function ieVersion(uaString) {
uaString = uaString || navigator.userAgent;
var match = /...

SSH: X-Forwarding

If you need to run a program on a remote machine with a graphical UI (and you trust the remote machine), you can use SSH X-Forwarding. I sometimes use this to connect to a virtual machine installed on my work PC from my home office.

Simply SSH to the remote machine (e.g. to your office PC) and add -X to the ssh call. Now, when you start a program with an UI (e.g. virtualbox) in that SSH session, a window will open on your local machine. It will not be particularly snappy, but on a decent connection it will be usable. …

Repeats

Rails: When to use :inverse_of in has_many, has_one or belongs_to associations

When you have two models in a has_many, has_one or belongs_to association, the :inverse_of option in Rails tells ActiveRecord that they're two sides of the same association.

Example with a has_many / belongs_to association:

class Forum < ActiveRecord::Base
  has_many :posts, :inverse_of => :forum
end

class Post < ActiveRecord::Base
  belongs_to :forum, :inverse_of => :posts
end

Knowing the other side of the same association Rails can optimize object loading so forum and forum.posts[0].forum will reference the same…

Repeats

Project management best practices: The story tracker

In general, the tracker should always be the definitive source of truth of what needs to be done as part of a project. If you identify a task that needs to be done, you should create a story. If you learn something that contradicts an existing story, change it.

The tracker can contain two types of stories: Developer stories, and non-developer stories.

Non-developer stories

Non-developer stories should be clearly marked. They usually belong to the PM (or maybe people from the operations team). Those story can take all forms, could just…

Repeats

Collect all values for a given column in an ActiveRecord scope

The Edge Rider gem allows you to collect an array of values for one field of your ActiveRecord elements:

>> User.active.collect_column(:id)
=> [1, 5, 23, 42]

It also comes with a :distinct option in case you are only interested in unique values:

>> Article.collect_column(:state, distinct: true)
=> ['draft', 'published']

In modern Railses (since 3.2) you can also use ActiveRecord's pluck met…

Repeats

Rails: How to use prepend to avoid monkey patches in modules

Let's say you have a gem which has the following module:

module SuperClient

  def self.foo
    'Foo'
  end
  
  def bar
    'Bar'
  end

end

For reasons you need to override foo and bar.

Keep in mind: Your code quality is getting worse with with each prepend (other developers are not happy to find many library extensions). Try to avoid it if possible.

  1. Add a lib/ext/super_client.rb to your project (Folder or file needs to be required in an initializer)
  2. Add the extension, which overrides both methods (prepend i…
Repeats

How to make changes to a Ruby gem (as a Rails developer)

At makandra, we've built a few gems over the years. Some of these are quite popular: spreewald (475k downloads), active_type (330k downloads), and geordi (210k downloads) for example (numbers from 2018).

Developing a Ruby gem is different from developing Rails applications, with the biggest difference: there is no Rails. This means:

  • no defined structure (neither for code nor directories)
  • no autoloading of classes, i.e. you need to require all files yourself
  • no [active_support](https://api.rubyonrails.org/classes/ActiveSupport.ht…
Repeats

Project management best practices: Project team responsibilities

In a project team for a bigger project people have several roles:

  • Developer: at makandra
  • Project lead: at makandra
  • Project manager (PM): at makandra, external, or with the customer. In a smaller project this person is also the project lead.
  • Product owner (PO): with the customer

Developer

  • Development
  • Take responsibility for their stories. This includes always gathering all necessary information from the project lead or the PM, communicate blockers, make sure stories are merged, deployed etc.
  • Tell the project lead, if you'r…

Rails: How to check if a certain validation failed

If validations failed for a record, and you want to find out if a specific one failed, you can do this via Rails.
You should rarely need this, as your error messages are usually good enough to display all necessary information to users.

As an example, consider the following model which uses two validations on the email attribute.

class User < ApplicationRecord
  validates :email, presence: true, uniqueness: true
end

And let's assume we have a blank user:

user = User.new
user.valid? # => false

The record's errors then…

External content

The Definitive Guide to Cookie Domains

Restricting access to cookies is essential for security in many web apps. For example, the session ID, the secret token used to identify a particular session, is typically stored in a cookie. Cookies have several important settings. Previously, I discussed the secure flag. This time, let’s dive into the cookie domain.

The cookie domain is an important security feature, probably even more important than the secure flag. It tells the browser that this cookie must only be sent to matching domains. Matching however, can happen in several w…

Repeats

Nested ActiveRecord transaction pitfalls

When working with custom transactions you may encounter unexpected behaviour if you try to roll back your changes.

tl;dr

Not all databases support nested transactions. Therefore, Rails will sometimes silently ignore a nested transaction and simply reuse the other transaction. However, a ActiveRecord::Rollback within the nested transaction will be caught by the block of the nested transaction, but will be ignored by the outer transaction, and not cause a roll back!
To avoid this unexpected behaviour, you have to explicitly tell rai…

External contentRepeats

How to write a good changelog

We want to keep a changelog for all gems we maintain. There are some good practices for writing a changelog that adds value, please stick to these.

  • Add a notice to the README's contribute section about the changelog
  • For every release update the changelog
  • Note the date format yyyy-mm-tt

What is a changelog?

A changelog is a file which contains a curated, chronologically ordered list of notable changes for each version of a project.

Why keep a changelog?

To make it easier for users and…

Repeats

HTML forms with multiple submit buttons

Most forms have a single submit button that will save the record when pressed.

Sometimes a form needs additional submit buttons like "accept" or "reject". Such buttons usually attempt a state transition while updating the record.

To process a form with multiple buttons, your server-side code will need to know which button was pressed. To do so you can give each submit button a different [formaction] attribute. This will override the …

Repeats

Best practices: Large data migrations from legacy systems

Migrating data from a legacy into a new system can be a surprisingly large undertaking. We have done this a few times. While there are significant differences from project to project, we do have a list of general suggestions.

Before you start, talk to someone who has done it before, and read the following hints:

Understand the old system

Before any technical considerations, you need to understand the old system as best as possible. If feasible, do not only look at its API, or database, or frontend, but let a user of the old system sho…

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