a friend of 后面用什么格

后面用宾格，表示某人是某人的朋友，of后面必须用物主代词。a friend of+名词性物主代词：表示...的朋友。在表示名词所有格时，s结构可以转换成of结构。比如：my father’s friend→the friend of my father’s。

例句

When it turned out that the winning bidder was a good friend of mine,I was very happy.

当得标结果是一位我的好朋友时，我非常高兴。

He was married to a friend of mine.

他以及我的一个朋侪结了婚。

Is a good friend of mine,our relations have been very good,but just yesterday we done one.

是我的好朋友，我们的关系一直很好，不过就在昨天我们大干了一架。

A friend of mine came to see me yesterday.

我的一个朋侪昨天来看我了。