The default value of an optional parameter must be constant. Dart

user_17981859 0
Viewed 465

I tried to make a default map parameter but it just goes errors for some reason,

var size = {
  "width": 1920,
  "height": 1080,
};

class MyClass {
  myFunction([String MyParam = "Sup!", Map background_size = size]) async {
    return background_size.width;
  }
}

It only gives me an errors like this The default value of an optional parameter must be constant. Can someone tell me which lines I type wrong?

dart
1 Answers

Solution 1

Define size as const

const size = {
  "width": 1920,
  "height": 1080,
};

class MyClass {
  myFunction([String MyParam = "Sup!", Map background_size = size]) async {
    return background_size.width;
  }
}

Solution 2

Set value if background_size is not set

var size = {
  "width": 1920,
  "height": 1080,
};

class MyClass {
  myFunction([String MyParam = "Sup!", Map? background_size]) async       {
    final _background_size = background_size ?? size;
    return _background_size.width;
  }
}
user_57977550
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