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Question

I'm making a registry page in an app I'm building. My issue is the logic that checks the database to see if an existing user already has the username that they are trying to register with. I get all the usernames in the database and loop through them in a for loop, and have an if statement to see if any match, heres the relevant code:

class RegistryValidator{

  static ErrorReporter validate(String userName, String password, String email){

    Services.getUserName().then((value) {//value = list<User> where User is a custom object
       for(var i = 0; i < value.length; i++){
         print(value.elementAt(i).userName);
         if (value.elementAt(i).userName == userName){
            print('FOUND A DUPLICATE'); //This prints
            return new ErrorReporter("Failure", "UserName already exists");
         // loop ends here and continues to else block
         }
       }
    });
   if (userName.length < 3){
     return new ErrorReporter("Failure", "UserName needs to be at least 3 characters long");
   }
   else if(userName.length > 20){
     return new ErrorReporter("Failure", "UserName needs to be at under 20 characters long");
   }
   else if(password.length < 8){
     return new ErrorReporter("Failure", "Password needs to be at least 8 characters long");
   }
   else if(password.length > 20){
     return new ErrorReporter("Failure", "Password needs to be at under 20 characters long");
   }
   else if(email.length > 50){
     return new ErrorReporter("Failure", "Choose a shorter email. We do not accept emails longer than 50 characters");
   }
   else if(!EmailValidator.validate(email)){
     return new ErrorReporter("Failure", "Invalid Email, please enter a valid email");
   }
   else{
     return new ErrorReporter("Success", "You Are Registered!");
   }
 }
}

The ErrorReporter class:

String status;
String errorDesc = "";
ErrorReporter(this.status, this.errorDesc);

and finally, inside of the onPressed() I have:

ErrorReporter reporter = RegistryValidator.validate(userNameController.text, passwordController.text, emailController.text);

For example, if I were to input a username that already exists within the database, calling reporter.status should give me "Failure", but I get "Success" everytime.

NOTE: I'm getting the expected behavior from the other if statements. However when a duplicate is found via for loop, the return only seems to work for exiting out of the for loop and not the function. Could anyone help me understand why it's acting this way?

Answer 1

Thanks to @jamesdlin, I figured out what I was doing wrong. First off, the reason the return call wasn't working in the for loop was because I was returning to the .then() call instead of .getUserName() , but even after fixing that up, I still wasn't getting the right results. That's because I wasn't waiting for the Future/function to finish. This is accomplished by using the await keyword before calling your Future. For anyone else that doesn't quite understand this yet, I found this site very helpful: https://dart.dev/codelabs/async-await