calculate discount of prices in flutter

Question

I want to try define below formula to calculate between old price and new price and show it on text widget but when i want to use it in an double variable i've got this error : "Only static members can be accessed in initializers" and this is what i want to do:

class ProductDetails extends StatefulWidget {
 final prod_fullName;
 final prod_pic;
 final prod_old_price;
 final prod_price;
 double percent=(prod_old_price - prod_price)/prod_old_price*100;
ProductDetails({
 this.prod_fullName,
 this.prod_pic,
 this.prod_old_price,
 this.prod_price,
});

@override
_ProductDetailsState createState() => _ProductDetailsState();
}
class _ProductDetailsState extends State<ProductDetails> {
 Row{
  child:new Text("$percent%");
}

Saman · Accepted Answer · 2020-01-18T16:49:57.673

4

class ProductDetails extends StatefulWidget {
  final String prod_fullName;
  final String prod_pic;
  final double prod_old_price;
  final double prod_price;

  const ProductDetails({Key key, this.prod_fullName, this.prod_pic, this.prod_old_price, this.prod_price}) : super(key: key);

  @override
  _ProductDetailsState createState() => _ProductDetailsState();
}
class _ProductDetailsState extends State<ProductDetails> {
  double percent;
  @override
  void initState() {
    percent=(widget.prod_old_price - widget.prod_price)/widget.prod_old_price*100;
    super.initState();
  }

  @override
  Widget build(BuildContext context) {
    return Text("$percent%");
  }
}

edited Jan 18 '20 at 16:49

answered Jan 18 '20 at 15:41

Saman

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dadash damet garm vali in khata ro mide : Class 'String' has no instance method '-'. – Mehrdad Hosseini Jan 18 '20 at 16:00
@MehrdadHosseini. جواب ویرایش شد. دقت که که همه پارامترها الزامی اند – Saman Jan 18 '20 at 16:50
ممنونم ازت الان تستش می کنم – Mehrdad Hosseini Jan 18 '20 at 17:05
type 'int' is not a subtype of type 'String' شما میدونی این خطا مربوط به چیه؟ – Mehrdad Hosseini Jan 18 '20 at 17:16

calculate discount of prices in flutter

1 Answers1