Is there a way to to show snapshot data based on object value in Dart / Flutter (REST)?-CodePudding

Narrowly related to this question:

How to fetch only items from JSON if certain object value is there

I want to show posts only if they contain number 1 in it.

JSON:

posts = '{"number":"1"}';

JSON is fetched in a separate file like:

    Place(Map<String, dynamic> json) : super(json) {
        posts = json["number"];
    }

And I have this:

  Widget _buildGridView() => StreamBuilder<List<Place>?>(
      stream: listPosts,
      initialData: [],
      builder: (context, snapshot) {
        if (snapshot.data != null) {
          return new GridView.count(
              children: List.generate(snapshot.data!.length, (index) {
                return _buildPlacesCell(snapshot.data![index]);
              }));
        }
      });

I am wondering: can I do something like this?

if (snapshot.data.posts.number = 1)

Instead of

snapshot.data != null

Or not?

I want to show my data only if the post has number 1 in it's JSON file, but I can't get this to work.

I am getting the following error:

error: The getter 'posts' isn't defined for the type 'List<Place>'

Edit: after Jamiu's snippet, getting the following errors:

error: The operator '[]' isn't defined for the type 'Place'.

and:

error: The body might complete normally, causing 'null' to be returned, but the return type is a potentially non-nullable type

Edit after your last update:

Now this has become a problem in a different widget:

error: Undefined name 'context'.

And:

onTap: () {
  HomeNav(context).open;
},

CodePudding user response：

//Try this

Map<String, dynamic> data = snapshot.data!.data() as Map<String, dynamic>;
if(data["number"]=="1"){
   //do
}

CodePudding user response：

You could nest the if statements. First, check if the snapshot.data != null and then inside that if statement, check if snapshot.data.posts.number = 1 like so:

if(snapshot.data!=null){
    if(snapshot.data.posts.number=1){
        return new GridView.count(
        children: List.generate(snapshot.data!.length, (index) {
        return _buildCell(snapshot.data![index]);
        }));
    }
}

Consider doing this:

StreamBuilder<List<Place>>(
    stream: listPosts,
    builder: (context, snapshot) {
        if (snapshot.connectionState == ConnectionState.waiting) {
            return const Center(child: CircularProgressIndicator());
        }
        if (snapshot.hasData) {
            final data = snapshot.data!;
            if (data.isNotEmpty) {
                return GridView.count(
                    children: List.generate(
                        data.length,
                        (index) {
                            if (data[index].number == '1') {
                                return _buildPlacesCell(data[index]);
                            } else {
                                return Visibility(
                                    visibile: false
                                    child: const SizedBox();
                                );
                                
                            }
                        },
                    ),
                );
            }else{
                return Visibility(
                    visible: false
                    child: const SizedBox();
                );
            }
        }
        if (snapshot.hasError) {
            print(snapshot.error);
            //! do any error handling here
        }
        return const Center(child: CircularProgressIndicator());
        },
    ),