AFAIK, Mapper doesn't define equality. You have to do that yourself as you would for any other Scala/Java class by overriding equals and hashcode. Using a Set (HashSet, specifically) seems like a pretty efficient way of doing this, although there may be a better way depending on your usage.
Derek On Wed, May 27, 2009 at 1:49 AM, valstadsve <[email protected]> wrote: > > Long time reader, first time poster. > > Also first time liftweb developer. I have an app that loads rows from > db using the Mapper framework, and displays them with a checkbox each. > I track which objects are checked by storing them in a collection. To > find the value of a checkbox (first argument to ajaxCheckbox), I do a > lookup to see if the respective object is in the collection. > > I have tried two collections for this purpose, and only one of them > works: (Names have been changed to protect... well, me) > > 1) Store mapped objects in a Set. This typically leads to: > > "check" -> ajaxCheckbox(coll.contains(a), v => { if (coll.contains(a)) > { // And so forth > > 2) Store mapped objects in a Map, using their id (a Long) as key. This > usually ends in: > > "check" -> ajaxCheckbox(coll.contains(a.id), v => { if ( coll.contains > (a.id)) { // And so forth and so forth > > As you might suspect from the subject of this post, only the second > strategy works as expected. Comparing id's is obviously more > reliable. Using sets and relying on object identity instead, the > checked objects render unchecked (and this is somewhat disturbing) > MOST of the time. My guess is there is some object management going on > behind the scenes, so that different requests deal with different > instances for the same rows. However, the equals/hashCode regime of > the Mother Platform _is_ supposed to resolve such things for > collections ... > > So, being all new to this, I have several questions: > > 1) Should object identity work for subclasses of Mapper and friends? > I.e. is this a bug? > > 2) Or am I expected to implement equality myself? > > 3) Are there better ways to track a long list of checkboxes? I have > noticed that GUI/network lag and asynchrony, the (first) a in ajax, > may produce twinkling checkboxes after a flurry of clicks... > > 4) Somewhat more far-fetched: Are collections in scala (gulp) not > using equals/hashCode? > > Other than that, I am impressed with liftweb and find it an excellent > introduction to Scala. Books are on order, too! > > Kjetil > > > > --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Lift" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/liftweb?hl=en -~----------~----~----~----~------~----~------~--~---
