Seaside WAAnchor fun
Written on June 14 2010.
This blog post was written a long time ago and may not reflect my current opinion or might be technically out of date. Read with a grain of salt.
I’m currently playing with Seaside (a Smalltalk web framework) for a pet project. As you maybe know, Seaside is, by default, not very friendly with URLs. I wanted to have bookmarkable URLs for user convenience and for search engine. Ramon Leon explains how he managed to get nice urls for his blog in a super-interesting blog post.
When playing with WAAnchor methods, I fought with a weird behaviour:
html anchor
callback: [self moveToPage: page];
useBaseUrl;
extraPath: page slug;
with: page title.
did not work, while
html anchor
useBaseUrl;
extraPath: page slug;
callback: [self moveToPage: page];
with: page title.
worked fine. Can you see the difference in these two snippets?
The reason of the resulting bug is quite simple but is hard to spot when you’re not careful: the method `useBaseUrl` should always be the first to be called in a method cascade on a WAAnchor. Indeed, both `extraPath:` and `callback:` will affect the url of the WAAnchor while `useBaseUrl` will reset it. This reset will cancel all the operations you’ve done before on the url of the WAAnchor.
Moral of the story: beware of side effect (or How I Learned to Stop Worrying and Love Functional Programming)