Groovy
Retrieve the first object (index [0]) among all objects attached to this page and of a certain class
obj = doc.getObject('XWiki.XWikiComments')
com.xpn.xwiki.api.Object@7fbb54ab
Retrieve all objects attached to this page and of a certain class and one of their properties
objs = doc.getObjects('XWiki.XWikiComments')
[com.xpn.xwiki.api.Object@58b3dea0, com.xpn.xwiki.api.Object@8dd07df, com.xpn.xwiki.api.Object@672fc604, com.xpn.xwiki.api.Object@71716588, com.xpn.xwiki.api.Object@4bc0fde7, com.xpn.xwiki.api.Object@6b5d6f8b, com.xpn.xwiki.api.Object@434645be, com.xpn.xwiki.api.Object@3a8cdf73, com.xpn.xwiki.api.Object@76a2150c]
objsAuthors = doc.getObjects('XWiki.XWikiComments').author
objsAuthor = doc.getObjects('XWiki.XWikiComments')[2].author
println objs[0].author
println objsAuthors
println objsAuthor