Blogs on Brian Mehrman

Ruby Code Blocks

Sun, 13 Jan 2019 00:00:00 -0500

Code Blocks

Ruby code blocks are from the closure family

Ruby blocks are found throughout ruby. They are a powerful feature that allow you to pass snippets of code to enumerable methods (e.g. each, select, detect) as well as custom methods useing the yield keyword.

Blocks are nothing new, they use the computer science concept called closures. This concept was invented by Peter J. Landin in 1964. Closures were adopted by a version of a Lisp called Scheme in 1975.

Postgresql Record Locking

Sat, 23 Jun 2018 00:00:00 -0500

Database Lock Modes

Postgresql provides different locking modes to control concurrency within the database. Locks are automatically acquired by most Postgres commands to make sure tables are not dropped or modified while a command is executed. Locks can also be acquired manually for application level control.

ActiveRecord provides the interface between the Rails application and the database. Using ActiveRecord we can create these database level locks.

Setup

For the examples in this post we will be using the following data setup with a new Rails application.

Optimistic vs Pessimistic Locking

Tue, 29 May 2018 00:00:00 -0500

Data integrity is at risk once two sessions begin to work on the same records…

Martin Fowler

Optimistic Locking

Is a data access strategy where it is assumed that the chance of conflict between sessions is very low. Changes from one session are validated before being committed to the database.

Pessimistic Locking

This an opposing data access strategy assumes that conflicts between sessions is highly likely. Conflicts are prevented by forcing all transactions to obtain a lock on the data (record or table) before it can start to use it.

Git Tips

Tue, 06 Feb 2018 00:00:00 -0500

Git

Git is a free version control system designed for both small and large projects.

Tips

Rebase

Whenever I am working on a project with other developers I find that I need to rebase my feature branch with the common branch the rest of the team is using. This branch is usually called dev or ci.

$ git fetch

To make sure I have the latest branches I run a fetch to update all my local branches.

class_eval vs define_method

Wed, 26 Apr 2017 00:00:00 -0500

Meta Programming

Having to write redundant methods can lead to hundreds of lines of code that can be hard to maintain. Meta programming provides us with tools that allow us to write code that writes its self.

Class Eval

class_eval opens the class and adds the method to the class itself. While this takes longer to define a method it puts the new method in the ancestor chain where it can be accessed quicker than if you used define_method.