How to sum only those objects of the array that require the status (true)-CodePudding

I have an array with such data (more data in reality)

         [ 
           {
                 serviceid: "979cf8e6",
                 amount: 1,
                 price: 11,
                 materialsPrice: 100,
                 enable: true,
                 chenge: true
            },
            {
                 serviceid: "979cf812",
                 amount: 1,
                 price: 15.5,
                 materialsPrice: 0,
                 enable: true,
                 chenge: true
            }
         ]

I want to match all "price" in an array in which change = true. Now I'm using this query for this.

   double get sumPay {
    double sum = listVariant
        .map((e) => e.price )
        .fold(0, (previousValue, price) => previousValue   price!);
    return sum;
  }

But this request sums up all the elements, and it will give me only those in which the status is change: true. I will be grateful for your help)

CodePudding user response：

Try this

   double get sumPay {
    var changeList = listVariant.where((e) => e.change == true);
    double sum = changeList
        .fold(0, (previous, next) => previous.price   next.price);
    return sum;
  }

CodePudding user response：

Before calling map funcrion use where funtion to select what you want:

   double get sumPay {
    double sum = listVariant
        .where((e) => e.change == true)
        .map((e) => e.price )
        .fold(0, (previousValue, price) => previousValue   price!);
    return sum;
  }

CodePudding user response：

Try below code:

void main() {
  List total = [
    {
      'serviceid': "979cf8e6",
      'amount': 1,
      'price': 11,
      'materialsPrice': 100,
      'enable': true,
      'chenge': true
    },
    {
      'serviceid': "979cf812",
      'amount': 1,
      'price': 15.5,
      'materialsPrice': 0,
      'enable': true,
      'chenge': true
    }
  ];

  var count = total.map((m) => m["price"]).reduce((a, b) => a   b);
  print(count );
}

CodePudding user response：

You can check if chenge is true pass price if not pass 0, so change this

double sum = listVariant
        .map((e) => e.price )
        .fold(0, (previousValue, price) => previousValue   price!);

double sum = listVariant
        .map((e) => e.chenge ? e.price : 0) //<--- add this
        .fold(0, (previousValue, price) => previousValue   price!);

or as @pskink mentions use where, like this:

double sum = listVariant
        .where((e) => e.chenge)
        .map((e) => e.price)
        .fold(0, (previousValue, price) => previousValue   price!);