This function has a nullable return type of 'String?' but ends without returning a value-CodePudding

I am trying to figure out why I get the Error in Title when adding if-Statements to my program. Without the if-statements everything works just fine. I hope someone can help me out :D Greetings


String? btmRechneranzeige(double? menge, double? prozent, String? btmittel,)  {
  // Add your function code here!
  var m = menge;
  var p = prozent;
  double mengebtm = 0;
  if (m != 0 && p != 0) {
    mengebtm = m! * (p! / 100);
  }

  var result = mengebtm.toString();

  String stoff = "";
  if(btmittel == null){
  return "...";
  }
  if (btmittel == "Amphetamin" && mengebtm >= 10) {
    stoff = "Amphetaminbase übersteigt die nicht-geringe Menge";
  } else {
    if (btmittel == "Amphetamin" && mengebtm < 10) {
      stoff = "Amphetaminbase übersteigt die nicht-geringe Menge nicht";
    } else {return null;}
  String output =
      "Bei einer Menge von $result gramm handelt es sich um eine geringe Menge!";
  //String result = nonono;
  return output;
}

CodePudding user response：

The brackets don't match up right, making paths that don't return anything. I suspect you want to change the line that says

} else {

} else

Although other things seem wrong as well. Like you don't even use the result of stoff

CodePudding user response：

  String? btmRechneranzeige1(double? menge, double? prozent, String? btmittel) {
    var m = menge;
    var p = prozent;
    String stoff = "";
    double mengebtm = 0;
    if (m != 0 && p != 0) {
      mengebtm = m! * (p! / 100);
    }
    var result = mengebtm.toString();
    if (btmittel == null) {
      return "...";
    } else if (btmittel == "Amphetamin" && mengebtm >= 10) {
      stoff = "Amphetaminbase übersteigt die nicht-geringe Menge";
    } else if (btmittel == "Amphetamin" && mengebtm < 10) {
      stoff = "Amphetaminbase übersteigt die nicht-geringe Menge nicht";
      String output = "Bei einer Menge von $result gramm handelt es sich um eine geringe Menge!";
      return output;
    } 
    return null; // this line optional
  }

CodePudding user response：

You are missing a return at this if-statement "btmittel == "Amphetamin" && mengebtm >= 10"

So this would work:

String? btmRechneranzeige(double? menge, double? prozent, String? btmittel,)  {
  // Add your function code here!
  var m = menge;
  var p = prozent;
  double mengebtm = 0;
  if (m != 0 && p != 0) {
    mengebtm = m! * (p! / 100);
  }

  var result = mengebtm.toString();

  String stoff = "";
  if(btmittel == null){
  return "...";
  }
  if (btmittel == "Amphetamin" && mengebtm >= 10) {
    stoff = "Amphetaminbase übersteigt die nicht-geringe Menge";
    return "some text here..." // -> This is the added line!!
  } else {
    if (btmittel == "Amphetamin" && mengebtm < 10) {
      stoff = "Amphetaminbase übersteigt die nicht-geringe Menge nicht";
    } else {return null;}
  String output =
      "Bei einer Menge von $result gramm handelt es sich um eine geringe Menge!";
  //String result = nonono;
  return output;
  }
} // You were also missing this bracket :D

When returning an instance of something make sure you add a return value (null is also a value) for each path, so every if (else) branch.