Extract unique values from existing json list to create unique listview builder

Question

I have a list (userData) which has json parsed values; I want to iterate through the list, and strip down a single key/value pair to reduce the list to a set of common values.

The userData list has json parsed data including countries and continents. I want to produce a reduced list of unique continents (and create a dynamic listview with this reduced list). See my side/drawer code below:

drawer: Drawer(
        // Add a ListView to the drawer with unique continents
        child: ListView.builder(
          itemCount: userData == null ? 0 : userData.length,
          itemBuilder: (BuildContext context, int index) {
            for (var item in userData) {
              continents.add(userData[item]['continent']);
            }
            continents.toSet().toList();

            return Container(
                width: 130,
                alignment: Alignment.center,
                child: Text(
                  "${continents[index]}",  //unique continent should be here
                  style: TextStyle(
                    fontSize: 20.0,
                    fontWeight: FontWeight.w500,
                  ),
                ));
          },
        ),
      ),

Thanks in advance for any assistance!

Thanks Josteve. Think of it like ``` List fruits = ['apple', 'orange', 'apple', 'pear', 'apple'];``` and I want to reduce this to a uniqueFruits = ['apple', 'orange', 'pear'] list (within a ListView widget). — Kolya Miller
– Kolya Miller, Commented May 5, 2020 at 22:59

Josteve Adekanbi · Accepted Answer · 2020-05-05 23:04:31Z

1

Assign continent back to continents.toSet().toList();

Like

continents = continents.toSet().toList();

answered May 5, 2020 at 23:04

Josteve Adekanbi

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