Grails 2.4.4将项目两次添加到一对多关系

Question

I have two classes in my model: Contribution (a commit) and Version (a versioned object in the commit). Contribution hasMany Version and Version belongsTo Contribution.

When I "commit" a new version, it creates a new contribution, a new version and contribution.addToVersions(version). This does something like:

1. contribution = new Contribution(...)
2. newversion = new Version(contribution: contribution, ...)
3..9. ...
10. contribution.addToVersion(newversion)

If a previous version exists for the same object, I do: (this goes in the ... of the previous snipet)

3. if (Version.countByUid(newversion.uid) > 0) {
4.   prevVersion = Version.findBtUid(newversion.uid)
5.   prevVersion.lastVersion = false
6.   prevVersion.save() <<<< THIS IS ADDING THE newversion TO contribution.versions
7. 
8.   newversion.updateVersion() // updates the las part of the uid
9. }

The problem is when I receive a new version of an existing one, line 6. adds the new version to the contribution.versions (very weird), then on line 10. the version is added again to that collection, so I end up with duplicated items in contribution.versions.

Any ideas why this is happening? Why saving another instance of Version affects the relationship of the new version and the new contribution?

My workaround was to just execute the addToVersions if there are not previous versions, but I want to know if this is actually a Grails bug buecause it doesn't make much sense.

Answer 1

The problem was the relationship between Version and Contribution is bidirectional, so when I set version.contribution and save the version, the version is added automatically by Grails to the contribution.versions list.

So if I also do the contribution.addToVersions, I end up with the version added twice to the contribution.version list.

Possible solutions are: not doing the addToVersions, or making the relationship unidirectional.