如何在 flutter/dart 中向列表项添加新属性？

Question

I have the following List

[
{thumb: 28986/H6a6Xkm_thumb.jpeg, full: 28986/H6a6Xkm.jpeg}, 
{thumb: 28986/f-2_thumb.jpg, full: 28986/f-2.jpg}, 
{thumb: 28986/Ft_thumb.jpg, full: 28986/Ft.jpg}, 
{thumb: 28986/FED_thumb.jpg, full: FED.jpg}
]

I wanted to try to add a new property to each of these 4 items called desc which would be a description, lets say for now: Apple

Is there an easy way to iterate the list and insert the new property so the final result would be:

[
{thumb: 28986/H6a6Xkm_thumb.jpeg, full: 28986/H6a6Xkm.jpeg, desc: Apple}, 
{thumb: 28986/f-2_thumb.jpg, full: 28986/f-2.jpg, desc: Apple}, 
{thumb: 28986/Ft_thumb.jpg, full: 28986/Ft.jpg, desc: Apple}, 
{thumb: 28986/FED_thumb.jpg, full: FED.jpg, desc: Apple}
]

Answer 1

Is your list a list of maps?

The easiest way to edit every value in a list is using the .map method:

myList = myList.map((value) => newValue).toList();

so for example say you have a list of numbers and want to add one to each of them

myList = myList.map((number) => number+1).toList();

you can also pass more calculations like so:

myList = myList.map((value) {
  // some calculations
  return newValue;
}).toList();

Here is how to solve your problem with that code assuming your list is List<Map<String, dynamic>>

myList = myList.map((value) => value..addAll({'desc': 'apple'})).toList();

Answer 2

Yes, you can iterate over the list with map method and inside it return the new map with the spread operator like this:

final myList = [{"hello": "world"}];
final newList = myList.map((obj) => {...obj, "desc": "Apple"}).toList();

Answer 3

You can use an for loop or the forEach list property to add an element to the lists:

void main() async {
  var list = [
    {'thumb': '28986/H6a6Xkm_thumb.jpeg', 'full': '28986/H6a6Xkm.jpeg'},
    {'thumb': '28986/f-2_thumb.jpg', 'full': '28986/f-2.jpg'},
    {'thumb': '28986/Ft_thumb.jpg', 'full': '28986/Ft.jpg'},
    {'thumb': '28986/FED_thumb.jpg', 'full': 'FED.jpg'}
  ];

   /// using for loop
  for (int i = 0; i < list.length; i++) list[i]['desc_for'] = 'Apple';
  print(list);
  
  /// Using forEach 
  list.forEach((item) {
    item['desc_forEach'] = 'Apple';
  });
  print(list);
}