Answer to null check question in painter's code

[feinstein]

The painter's code have this question:

  if (image != null && imageFit != null) {
    // TODO: why the ! are needed here, as check against null been performed?

The answer is, the compiler can't know if a class' filed is always null or not, because this field could be a getter that returns null sometimes and returns a value other times. You need to use the ! operator or you can copy that field to a local variable and check that variable, then the compiler knows it's not null at all.

Example:

  final image = this.image;
  if (image != null && imageFit != null) {
    // compiler knows image is not null and you don't need to use the ! operator.

[vintage]

Thanks! Labeling it as good first issue. If you or anyone else want to make the PR to resolve that, I'm happy to merge!

[feinstein]

No need to fix, it's just a preference of style. Copying to a local variable is safer, but just for extreme cases.