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@45fa9fe2
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@3f01410d, com.xpn.xwiki.api.Object@6b55dccb, com.xpn.xwiki.api.Object@5212ca7a, com.xpn.xwiki.api.Object@4fab39ae, com.xpn.xwiki.api.Object@7257f75e, com.xpn.xwiki.api.Object@6d3176f7, com.xpn.xwiki.api.Object@4a798a22, com.xpn.xwiki.api.Object@715be460, com.xpn.xwiki.api.Object@47ee94c4]
objsAuthors = doc.getObjects('XWiki.XWikiComments').author
objsAuthor = doc.getObjects('XWiki.XWikiComments')[2].author
println objs[0].author
println objsAuthors
println objsAuthor