The switch case expression type 'Type' must be a subtype of the switch expression type 'BankEvent'

Question

I am getting this error when I try to use switch case in dart. I have an abstract class and two classes extending it. See the code below

abstract class BankEvent{}

class FetchBanks extends BankEvent{}

class DeleteBank extends BankEvent{
  final int bankId;
  DeleteBank(this.bankId);
}

I have to make some implementations inside the handleEvents method depends on the instance of the class I am receiving as parameter. But I am getting the error (The switch case expression type 'Type' must be a subtype of the switch expression type 'BankEvent') in the case statement of switch case. My code for the switch case implementation is below

handleEvents(BankEvent bankEvent){
    switch(bankEvent){
      case FetchBanks:
        break;
    }
  }

Solution

Yeah finally I found the answer after a bit of research.It should be writtern as below

handleEvents(BankEvent bankEvent){
    switch(bankEvent.runtimeType){
      case FetchBanks:
        break;
    }
  }

Comments

[markspace]

Not sure. At first pass, FetchBanks is of type Class, which might be causing the error. Try modify the switch in either respect and see if it removes the error.

[Jarin Rocks]

I am not getting your point

[markspace]

For example, in the switch statement, replace switch(bankevent) with switch(bankevent.getClass()).

[Michael Horn]

If you're looking for something similar to sealed classes in Kotlin or enums in Swift, you may be interested in the freezed package: pub.dev/packages/freezed. Otherwise, the if-else approach is the way to go

[Jarin Rocks]

If else approach is working fine. But if there are many events then switch is the better way right. I will look in to freezed package.

[Michael Horn]

That's javascript type checking - The dart way to check the type is if (bankEvent is FetchBank) {...}

[Jarin Rocks]

@MichaelHorn stackoverflow.com/a/71529798/8192246

[andrestascon]

Thanks for the info, the question had the java tag which disoriented me