how to check if variable is null in dart?

Question

I am new to dart. I want to do something like this. But editor says it is 'unnecessary_null_comparison'. What is the best way in dart to do something like this?

 EventType? et = dbHandler.getEventType(widget.eventName) as EventType;
 if (et != null) {
   dbHandler.insertEventType(eventType);
 }

Alexandre Ardhuin · Accepted Answer · 2022-03-18 16:02:14Z

2

If dbHandler.getEventType(widget.eventName) returns a nullable value you should use as EventType?. Then your code should work as expected.

EventType? et = dbHandler.getEventType(widget.eventName) as EventType?;
if (et != null) {
  dbHandler.insertEventType(et);
}

answered Mar 18, 2022 at 16:02

Alexandre Ardhuin

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1 Comment

Aayush Sahay Jun 28 at 18:32

So, you just check if it is null like any other language, by comparing with the null keyword? Can no null safety signs help here to make it a bit shorthand?

E. Sun · Accepted Answer · 2022-03-18 16:01:22Z

2

Dart has sound null safety so when you casted it to EventType using as EventType, it is not nullable by definition, that's why it's saying the null comparison is unnecessary because it'll always evaluate to true.

answered Mar 18, 2022 at 16:01

E. Sun

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