I have created a register screen and am using the ROOM database to store the users. I am successfully adding them to the database. I am trying to run some validation on the entries as I do not want users to have the same username or email. Here is my code for adding them to the database and how I am validating it.

this is the function that sends the firstName, lastName, userName, password, address, city, postalCode, email, phone to the database.

the mCustomerViewModel.addCustomer(customer), returns a Boolean:

1. if it's true User Added

2. if its false, duplicate user

   val customer = Customer(0, firstName, lastName, userName, password,address,city,postalCode,email,phone)
   val flag = mCustomerViewModel.addCustomer(customer)
   println("FLAG ---> " flag)
   
   if(flag.equals(true)){
       Toast.makeText(applicationContext, "Success", Toast.LENGTH_SHORT).show()
   }else{
       Toast.makeText(applicationContext, "Failed", Toast.LENGTH_SHORT).show()
   }
   

here is the CustomerViewModel class:

fun addCustomer(customer: Customer){
    viewModelScope.launch(Dispatchers.IO){
        repository.addCustomer(customer) // call to CustomerRepository 
    }

and then from CustomerViewModel class, we call CustomerRepository

fun addCustomer(customer: Customer): Boolean {
    try {
        customerDao.addCustomers(customer)
        return true
    }catch (ex: Exception){
        return false
    }
}

As you can see, in my function where the customer is being added, I have a print statement println("FLAG ---> " flag) to check and see what the function was returning. I got this in the console:

When I run the app, the if statement doesn't run, only the else block does, because "flag" actually does not equal "true".

How can i fix this?

CodePudding user response：

Your addCustomer function launches a coroutine and doesn't return anything (except the implicit Unit). Notice you did not define any return type. It is not possible for a non-suspend function to return the result of a launched coroutine because it returns before the coroutine necessarily has been run yet. You should either turn it into a suspend function that directly calls repository.addCustomer(customer) without launching another coroutine, or you can give it a callback parameter to call at the end of the launched coroutine.

Third option is to change viewModelScope.launch to return viewModelScope.async and make the function return type Deferred<Boolean>. Then when you need the result, you can call await() on the Deferred in a coroutine.