颤动 - 如果然后其他 - 变量只在本地

Question

正如你在下面的代码中看到的，我想检查一个字符串是否有 ? 以他的名义。 如果是，我将其删除。 我的问题是变量 'nameOfFileOnlyCleaned' 保留在本地并且在 if else 之后为空。 谢谢您的帮助。

 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();

Answer 1

您应该在 if/else 语句之前定义变量，如下所示：

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

---

例如：

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

它返回：作为结果进行test 。