Rails 3 → 4 Upgrade

Legacy upgrade. Rails 3.2 is past EOL (Rails 3 LTS exists but is paid). The 3.2 → 4.0 hop is API-breaking; budget for a real project, not a weekend.

The opinion

Dual-boot with next_rails. Hop 3.2 → 4.0 → 4.1 → 4.2. Ruby 1.9.3+ required for the whole 4.0–4.2 series (Rails' own gemspec never raised the floor within Rails 4); 2.0 was merely "preferred," per the Rails 4.0 release notes. Use the protected_attributes gem as a temporary bridge from attr_accessible to strong parameters.

The hop sequence

3.2 → 4.0 → 4.1 → 4.2

Core patterns

Pattern 1: 3.2 → 4.0