Explanation of the method Date::once in the ruby core classes. This talk was originally given at the TSOT Ruby on Rails Project Night

1. Inside Date.once
Understanding some of the more interesting
code in the Ruby core

2. The Problem

3. The Problem
Instances of Date are immutable

4. The Problem
Instances of Date are immutable
Many methods involve complex calculations

5. The Problem
Instances of Date are immutable
Many methods involve complex calculations
Caching of results is desirable

6. The Problem
Instances of Date are immutable
Many methods involve complex calculations
Caching of results is desirable
Want to keep the code clean and uncluttered
with caching related code