flutter - if then else - variable made local only

Question

As you can see in the code below, I want to check if a string has a ? in his name. If yes, I remove it. My problem is that the variable 'nameOfFileOnlyCleaned' stay local and is empty after the if else. Thank you for your help.

 String nameOfFile = list_attachments_Of_Reference[j].toString().split('/').last;

      if (nameOfFile.contains('?')) { //Removes everything after first '?'
        String nameOfFileOnlyCleaned = nameOfFile.substring(0, nameOfFile.indexOf('?'));
      } else{
        String nameOfFileOnlyCleaned = nameOfFile;
      }

//Here my variable 'nameOfFileOnlyCleaned' is empty. 
This is a problem because the value should be used later 
in the code. Do you know why I have this issue please? 
Many thanks.

      String extensionFile = nameOfFileOnlyCleaned.split('.').last;
      
      String url_Of_File = list_attachments_Of_Reference[j].toString();

because your String is inside the if/else statement and you should have the variable on a upper scope. I recommend to read about general Object Oriented Programming principals to understand scope. — Mariano Zorrilla
– Mariano Zorrilla, Commented Jul 30, 2021 at 14:27
Thank you. I have declared those variables before the class. So I thought that it could be available every where in the class. But I do not know how to fix this. — Laurent Thomas
– Laurent Thomas, Commented Jul 30, 2021 at 14:31
They need to be inside the class but outside the if/else statement. You have to declare them as "late" or optional (using ?) — Mariano Zorrilla
– Mariano Zorrilla, Commented Jul 30, 2021 at 15:24

Abbasihsn · Accepted Answer · 2021-07-30 14:42:49Z

2

you should define your variable before if/else statement as follows:

String nameOfFileOnlyCleaned = "";
if (nameOfFile.contains('?')) { //Removes everything after first '?'
        nameOfFileOnlyCleaned = nameOfFile.substring(0, nameOfFile.indexOf('?'));
      } else{
        nameOfFileOnlyCleaned = nameOfFile;
      }

for example:

String nameOfFile = "test?test";
  String nameOfFileOnlyCleaned;
      if (nameOfFile.contains('?')) { //Removes everything after first '?'
        nameOfFileOnlyCleaned = nameOfFile.substring(0, nameOfFile.indexOf('?'));
      } else{
        nameOfFileOnlyCleaned = nameOfFile;
      }
  
  print(nameOfFileOnlyCleaned);

it returns: test as a result.

edited Jul 30, 2021 at 14:42

answered Jul 30, 2021 at 14:32

Abbasihsn

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5 Comments

Laurent Thomas Over a year ago

Thank you. I have tried, but my variable nameOfFileOnlyCleaned remain empty. I still not understanding why.

Abbasihsn Over a year ago

I just checked the result, it works fine, for example you can check the example (I have updated my answer). Please check the value of list_attachments_Of_Reference[j].toString().split('/').last;

Laurent Thomas Over a year ago

Fantastic. It works. Many thanks for your help. It is appreciated.

Uwe.Schneider Over a year ago

Could you give a reason, why it needs to be defined like this?

Abbasihsn Over a year ago

@Uwe.Schneider search for variable scope in if-statements in dart. Defining a variable inside if-statement is specifically for that scope in some programming languages such as C, Dart, etc. But for example in Python, you wont have this problem

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