如何从dart中的列表中添加两个值

  const pizzaPrices = {
    'margherita': 5.5,
    'pepperoni': 7.5,
    'vegetarian': 6.5,
  };
  const order = ['margherita', 'pepperoni'];
  var total=0.0;
  order.forEach((item){
    total+=pizzaPrices[item]??0.0;  
  });
  print("Total : "+total.toString());

有几种方法可以计算总数。一种方法是使用 fold

final total =
    order.fold<double>(0.0, (prev, elem) => prev + pizzaPrices[elem]!);

另一种方法是循环检查订单,并按要求将总数相加:

var total = 0.0;
for (final elem in order) {
  total += pizzaPrices[elem]!;
}

为了添加到您的列表中,您可以调用 add 列表中的方法:

order.add('vegetarian');

但是, const 无法修改列表,因此您必须进行更改 order 宣布为 final 或 var :

final order = ['margherita', 'pepperoni'];

因此,如果您使用它,就不必定义自己的“fold”函数。

var sum = [1, 2, 3].reduce((a, b) => a + b);

您可以访问此网站以获得更清晰的信息, https://github.com/dart-lang/sdk/issues/1649

num sum = 0;
for (num e in [1,2,3]) {
  sum += e;
}

  const pizzaPrices = {
    'margherita': 5.5,
    'pepperoni': 7.5,
    'vegetarian': 6.5,
  };
  const order = ['margherita', 'pepperoni'];
  
  var total=0.0;
  order.forEach((item){
     pizzaPrices.forEach((name,price){
       if(name==item){
         total=total+price;
       }
     });
  });
  
  print("Total : "+total.toString());
  

void main() {
  const pizzaPrices = {
    'margherita': 5.5,
    'pepperoni': 7.5,
    'vegetarian': 6.5,
  };

  var x = pizzaPrices['margherita'];
  var y = pizzaPrices['pepperoni'];

  List xy = [];

  xy.add(x);
  xy.add(y);

  double somme = 0;

  xy.forEach((var element) => somme += element);

  print(somme);
}