Mistakes? I've had a few

Andrew Grimm@andrewjgrimm

Excessively large classes

CausesAdding new features

Fear of passing around data

Not a problem until modifying existing code was required

Excessively large classes

Break into smaller classes

Or modules if you must

def_delegator :@sub_object, :method_foo

Side effects

Does your method really need to produce output? Can't it produce a string instead?

You can manipulate strings. You can't manipulate output.

Side effects

When testing, how often are you interested in writing to file or writing to a DB?

Aren't you interested in the contents instead?

Side effects

Side-effect-free code is easier to test, faster to test, and safer to test

Schlemiel the painter

Doing something a million times you only need to do a few times (literally!)

Often the result of mixing separate tasks together

Why maintainability matters

Additional functionality

Modifying functionality

Improving performance

Testing

If you can't write tests, it may not mean you're bad at testingIt may mean the production code is bad

Version control

Best form of documentation I had

What was I thinking when I wrote that code?

Large commits are a code smell