SDK Error

[rhymelph]

SDK version

2.5.0

You can use this code and run it.

void main(){
 Test test=Test.fromMap(null);
//throw Exception
}

class Test{
 String id;
 String name;
 Test();

 factory Test.fromMap(Map map)=>map==null?Test():Test()
 ..id=map["id"]
 ..name=map["name"];
}

result:

E/flutter ( 7677): [ERROR:flutter/lib/ui/ui_dart_state.cc(148)] Unhandled Exception: NoSuchMethodError: The method '[]' was called on null.
E/flutter ( 7677): Receiver: null
E/flutter ( 7677): Tried calling: []("id")
....

[eernstg]

Try this:

void main() {
  Test test = Test.fromMap(null);
//throw Exception
}

class Test {
  String id;
  String name;
  Test();

  factory Test.fromMap(Map map) => map == null ? Test() : (Test()
    ..id = map["id"]
    ..name = map["name"]);
}

The problem is that you are using a cascade whose receiver (that is, e in an expression e..s where s is a <cascadeSection>) is not the object obtained from Test() but rather the one from map == null ? Test() : Test().

It is a known source of confusion that cascades have such a low precedence. However, if we want to allow the right hand side of a cascade assignment to contain a wide assortment of expressions then the precedence has to be low. In particular, with e1..x = e2, e2 must be an <expressionWithoutCascade>, and that's nearly any expression.

[rhymelph]

@eernstg thank.

[eernstg]

Thanks! For prior discussions about the precence of the cascade syntax, please follow #608 (that's an old issue which was moved here from the SDK repository, so it's much older than the number 608 would imply).