if has bad state return something else Flutter-CodePudding

So I have a method in my controller that calculates me how many values I have in total

  get gesamtAnzahl => _products.entries
  .map((product) => product.value)
  .toList()
  .reduce((value, element) => value   element)
  .toStringAsFixed(2);

the problem is that I get each product pretty late So it has a bad state when I try to calculate these values at a time where no product exists

I tried doing something like this

"${controller.gesamtAnzahl == null ? "0" : controller.gesamtAnzahl}"

but I still get the bad state: no element error

what can I do to fix it?

CodePudding user response：

The problem here is that reduce wants at least one element. If you don't have any elements it will therefore fail. You could instead use fold which have a starting value that can be returned in case no elements are found.

There are also some other questionable code in your example but something like this should work:

  get gesamtAnzahl => _products.values
  .fold<int>(0, (value, element) => value   element)
  .toStringAsFixed(2);

Should be noted that this would only work if you actually wants "0.00" to be returned in case _products are empty.