The son of wealthy wine magnates sentenced to 300 hours of community work and ordered to pay $5000 after assaulting a police officer should have gone to prison, the police association says.

A wine-making rich-lister's son has sworn off alcohol since assaulting a female police officer in "serious violent attack".

Nikolas James Posa Delegat, 19, appeared for sentencing before Judge Kevin Phillips in the Dunedin District Court on Monday.

The first-year University of Otago student told a female officer "get off me, cop" before punching her in the face, and several more times after she lost consciousness.

HAMISH MCNEILLY / FAIRFAX NZ Nikolas James Posa Delegat, 19, in the dock of the Dunedin District Court.

"It nearly destroyed her life," Judge Phillips said.

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It was "a serious violent attack", the judge said of the alcohol-fuelled incident outside the popular Dunedin student haunt, Starters Bar, about 11pm on March 26, 2015.

HAMISH MCNEILLY/FAIRFAX NZ Starters Bar in Dunedin's student quarter.

The court heard Delegat "became enraged" at a comment made by a male associate about his girlfriend, and punched a hole in the bar's window.

That led to an argument, with Delegat punching a University of Otago Campus Watch officer, after he tried to intervene.

A passing police patrol noticed the disturbance and stopped to help.

​Constable Alana Kane, who was in court for the sentencing, suffered a black eye and serious swelling to her face after being punched by Delegat.

She spent 15 hours at Dunedin Hospital after the incident, was off work and could not drive for two months and still suffered headaches.

In her victim impact statement, Kane said Delegat showed no remorse and she believed she was "very lucky" to have escaped without more injuries.

Name suppression was initially sought for fair trial and personal hardship reasons, and was declined on both grounds.

His Auckland-based lawyer, Mark Ryan, applied for a discharge without conviction but it was declined.

﻿Ryan argued a conviction would stop Delegat pursuing a Financial Markets Authority career and he would be unable to race in yachting competitions in the United States.

Delegat took part in a restorative justice conference with one of the attending police officers, but Kane did not attend.

A letter of apology sent in April 2015 was never received by Kane, and if she had received that letter "her view may have been different", his counsel said.

Ryan said his client had done everything asked of a young man following this "one-off fall of grace".

"This incident was completely out of character."

Delegat had sought medical help and stayed off alcohol since the incident.

Ryan said his client wanted to work alongside authorities with young people involved in the "out-of-control drinking culture" at the University of Otago.

"He has addressed his demons and done a lot more than an average person in his position," Ryan said.

Delegat is the son of winemaker Jim Delegat, who with his sister Rosemari, is estimated to be worth $450 million by the National Business Review.

The judge sentenced Delegat to 300 hours' community service and ordered him to pay a $5000 emotional harm repayment.