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@3ee379ad
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@652a20a3, com.xpn.xwiki.api.Object@30c4e138, com.xpn.xwiki.api.Object@4d9e3c8b, com.xpn.xwiki.api.Object@4f98f17c, com.xpn.xwiki.api.Object@42162cb7, com.xpn.xwiki.api.Object@3dd1c446, com.xpn.xwiki.api.Object@16acef5f, com.xpn.xwiki.api.Object@3397519a, com.xpn.xwiki.api.Object@136e6fec]
objsAuthors = doc.getObjects('XWiki.XWikiComments').author
objsAuthor = doc.getObjects('XWiki.XWikiComments')[2].author
println objs[0].author
println objsAuthors
println objsAuthor