My plugin/gem selection guidelines:
- Does it have a well defined goal?
- Does it do something substantial?
- Does it have a good record?
If the plugin you are evaluating does everything, that isn't necessarily a good thing. A plugin that does everything will likely to be harder to debug and has a higher chance of conflicting with something. A plugin that does one thing has a much better chance of doing that one thing very well.
Does the plugin/gem do something substantial?
If the task at hand is pretty simple it may be better to write the code yourself. When you are faced with a rails update, maintaining a few extra lines of code could end up being a lot easier than finding the latest version of the plugin and making sure the new version is compatible with your application.
Does the plugin/gem have a good record?
Does the plugin appear to be well maintained or has it been years since it was updated? Does it only have one contributor or does it have a good community built around it?
Example 1: Chronic (chronic.rubyforge.org)
Does Chronic have a well defined goal?
Yes, Chronic is a natural language date/time parser.
Does Chronic do something substantial?
Yes, it would take a lot of work to write a natural language date/time parser.
Does Chronic have a good record?
It looks pretty good, it has been around for a couple years, quite a few people seem to be using it, and it has survived several rails upgrades without big issues.
Looks like Chronic meets the guidelines fairly well. I have been using Chronic quite successfully for about a year and a half.
Example 2: Facets (facets.rubyforge.org)
Does Facets have a well defined goal?
No, it is an attempt to do just about everything.
Does Facets do something substantial?
Not really, it does a lot, but it is made up of lots of little pieces.
Does Facets have a good record?
Yes and no, it has a substantial community behind it which is good, it has been around for a little while which is good, but it has also had some very large structural changes which made different versions incompatible.
Looks like Facets doesn't meet the guidelines, based on that I would not choose to use Facets in one of my rails apps. Facets is a gem that came built into some apps that I work with, I have had a lot of problems with Facets and how it was used.
Example 3: file-tail (file-tail.rubyforge.org)
Does file-tail have a well defined goal?
Yes, it allows you to tail a file without having process the output of a system tail application.
Does file-tail do something substantial?
Yes, it would be a bit of work to write your own tail library in ruby.
Does file-tail have a good record?
Yes and no, it has been around for quite some time and seems to be very stable, but it doesn't have a big community and I haven't found many people that talk about using it.
File-tail doesn't meet all the guidelines perfectly but it should be reasonably safe. I recently used File-tail in an application and it has performed very well so far.