我如何在飞镖中访问列表元素[关闭]

Question

我有构造函数列表。例如，

final data = [
      new sale(price: 5, numOfSales: 1),
      new sale(price: 10, numOfSales: 2),]

如何在列表上循环并访问 numOfSales 对其进行一些操作。

Answer 1

如果您尝试从数据数组中计算总 numOfSales，您可以这样做 你可以使用折叠data.fold(0, (t, e) =>( t as int) + e.numOfSales)

 void main() {

  final data = [
      new sale(price: 5, numOfSales: 1),
      new sale(price: 10, numOfSales: 2),
  ];
  
 final totalNumOfSales= data.fold(0, (t, e) =>( t as int) + e.numOfSales);
  print(totalNumOfSales);
    
}

class sale{
  final int price;
  final int numOfSales;
  
  sale({this.price=0, this.numOfSales=0});
  
  @override
  toString()=>'price: $price, numOfSales: $numOfSales';
  
}