kotovalexarian-likes-github
/
paper-trail-gem--paper_trail
mirror of https://github.com/paper-trail-gem/paper_trail.git
1
0
Fork 0
Code Releases Activity

Add info on diffing.

This commit is contained in:
Andy Stewart 2010-06-23 11:47:56 +01:00
parent 2a4550807c
commit 4aa1c989a5
1 changed files with 20 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

20
README.md
View File

@ -220,6 +220,26 @@ You can also store any information you like from your controller. Just override
Remember to add those extra columns to your `versions` table ;)
## Diffing Versions
When you're storing every version of an object, as PaperTrail lets you do, you're almost certainly going to want to diff those versions against each other. However I haven't built a diff method into PaperTrail because I think diffing is best left to dedicated libraries, and also it's hard to come up with a diff method to suit all the different possible use cases.
You might be surprised that PaperTrail doesn't use diffs internally anyway. When I designed PaperTrail I wanted simplicity and robustness so I decided to make each version of an object self-contained. A version stores all of its object's data, not a diff from the previous version.
So instead here are some specialised diffing libraries which you can use on top of PaperTrail.
For diffing two strings:
* [htmldiff](http://github.com/myobie/htmldiff): expects but doesn't require HTML input and produces HTML output. Works very well but slows down significantly on large (e.g. 5,000 word) inputs.
* [differ](http://github.com/pvande/differ): expects plain text input and produces plain text/coloured/HTML/any output. Can do character-wise, word-wise, line-wise, or arbitrary-boundary-string-wise diffs. Works very well on non-HTML input.
* [diff-lcs](http://github.com/halostatue/ruwiki/tree/master/diff-lcs/trunk): old-school, line-wise diffs.
For diffing two ActiveRecord objects:
* [Jeremy Weiskotten's PaperTrail fork](http://github.com/jeremyw/paper_trail/blob/master/lib/paper_trail/has_paper_trail.rb#L151-156): uses ActiveSupport's diff to return an array of hashes of the changes.
* [activerecord-diff](http://github.com/tim/activerecord-diff): rather like ActiveRecord::Dirty but also allows you to specify which columns to compare.
## Turning PaperTrail Off/On
Sometimes you don't want to store changes. Perhaps you are only interested in changes made by your users and don't need to store changes you make yourself in, say, a migration -- or when testing your application.