How to add data using loop in list in Flutter

Question

I have a 2-d list, I am adding data using `

quotationList.add( [productName.text, double.parse(productPrice.text), _n] );`

output is:

[[qwe, 555.0, 1], [qwe 1, 5555.0, 2]]

now i want to add this 2-d list into my products list, i can't figure out how to do that? my products list looks like this, with static data

final products = <Product>[
    Product('1', "random text", 3.99, 2),
    Product('2', "random text", 15, 2),
    Product('3', "random text", 6.95, 3),
    Product('4', "random text", 49.99, 4),
  ];

i want to make make it dynamic using some loops or something, like this

final products = <Product>[
    for(int i=0; i<quotationList.length; i++)
    {
      Product(i.toString(), quotationList[i][0], quotationList[i][1], quotationList[i][2]),
    }
];

but i got this error

The element type 'Set<Product>' can't be assigned to the list type 'Product'.

halfer · Accepted Answer · 2022-03-12 11:47:57Z

3

The issue is the {} braces for the for loop inside the list.

Change it to:

final products = <Product>[
      for (int i = 0; i < quotationList.length; i++)
        Product(
          i.toString(),
          quotationList[i][0],
          quotationList[i][1],
          quotationList[i][2],
        ),
    ];

The loops inside lists and maps don't have {}, because there aren't multiline.

edited Mar 12, 2022 at 11:47

halfer

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answered May 18, 2020 at 17:08

Hemanth Raj

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Comments

camillo777 · Accepted Answer · 2020-05-19 06:41:57Z

2

this is a full working code:

void main() {
  List quotationList = List();
  quotationList.add(["name1", 10.0, 100]);
  quotationList.add(["name2", 10.0, 100]);
  quotationList.add(["name3", 10.0, 100]);
  quotationList.add(["name4", 10.0, 100]);

  List products = quotationList
      .asMap()
      .map((index, quotation) => MapEntry(
          index,
          Product(
            index,
            quotation[0].toString(),
            quotation[1],
            quotation[2],
          )))
      .values
      .toList();

  for (Product p in products) print(p.name);
}

class Product {
  final int index;
  final String name;
  final double price;
  final int n;

  Product(this.index, this.name, this.price, this.n);
}

Hope it helps!

The conversion from List to Map is needed (asMap) because you need an index as well. If you do not need an index you can use the map method directly on the list.

edited May 19, 2020 at 6:41

answered May 18, 2020 at 17:14

camillo777

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2 Comments

ImAZ Over a year ago

can explain this code? what asMap and map functions are doing?

camillo777 Over a year ago

Hello @ImAZ there are some useful and compact function to manipulate list and maps. Map method is enumerating all list values allowing to make something with it. In this case because you need an index, is needed to transform the list into a map: from ["a","b","c"] to [0: "a",1: "b", 2:"c"]; when you are done you have to translate it into a List again; you can see here codeburst.io/… for example or on Dart reference: api.dart.dev/stable/1.10.1/dart-core/List/map.html

M.B · Accepted Answer · 2020-05-18 17:14:50Z

1

try this

final products = [
    for(int i=0; i<quotationList.length; i++)
    {
      Product(i.toString(), quotationList[i][0], quotationList[i][1], quotationList[i][2]),
    }
];

answered May 18, 2020 at 17:14

M.B

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