Class loading methods
1. “Classic”: explicit require and manual dependencies resolution.
Pros: no bugs.
Cons: lazy programmers want to write and maintain less code.
2. “Rails method” (dependencies.rb): catch const_missing in runtime, guess the file name, load it.
Pros: zero-configuration, good automatic dependencies resolution.
Cons: file name guessing is a constraint, hard to debug runtime threading issues.
3. “Merb method” (load everything in a loop, reload failed files):
Pros: zero-configuration, moderate automatic dependencies resolution, no threading issues, issues are explicit and may arise in a bootstrap process only.
Cons: twice loaded constants yield warning, hidden repeated configuration bugs may appear.
4. “io language method” (load everything sorted by filename):
Pros: no bugs, zero-configuration, easy to understand, optional manual dependencies resolution.
Cons: 2-5% of files are named with ugly prefixes like A0_message.io (higher priority) or Z_exceptions.io (lower priority).
Note: no method saves you from manual resolution of the two-way referencing issue (when A references B and B references A). You still have to create a special “header” file to put bootstrap definitions into.
Conclusion: Merb method is essentially Io method with additional “feature” (which is buggy by nature) of double loading files in case of LoadError. If you name your files according to Io method and resolve all interdependencies manually, Merb will load them once and in the correct order.