How to disable validation rule?

Question

Yii

There is a field that is mandatory.
The task is to make it mandatory when adding a record and optional when editing (if left empty, just do not change)
That is, somehow disable the required rule from actionUpdate I
forgot to clarify that yii2

Answer 1

Got it!
In rules() we replace
with
having previously added a constant
and in the actionCreate () method we write
$model->scenario = Administrator::SCENARIO_CREATE;

Answer 2

['field', 'require', 'on'=>'insert'],
['fied', 'safe', 'on'=>'update']
if we are talking about the first yii