CODEWITHSUNDEEP
dartflutter
David
David

Reputation: 103

How do i receive a future value as String

I am trying to receive the return value of the future as a string. How do i go about it.

//Get a stock info
Future<String> getStock(int productID) async{
  var dbClient = await db;
  var result = await dbClient.rawQuery('SELECT * FROM $tableStock WHERE $columnProductID = $productID');
  if(result.length == 0) return null;
  return Stock.fromMap(result.first).currentStock;
}


Widget _buildProductInfo(Product data){
    return Container(
      child: ListView(
        padding: EdgeInsets.all(8.0),
        children: <Widget>[
           _infoRow('Product ID', data.name),
           _infoRow('Product Name', data.productID),
           _infoRow('Cost Price', data.costPrice),
           _infoRow('Selling Price', data.salePrice),
           _infoRow('CategoryID', data.categoryID),
           _infoRow('Currrent Stock', db.getStock(int.parse(data.productID)))
        ],
      ),
    );
  }

I expect this code to show a "value" rather it says "Instance of Future". But i can print the returned value when i try

final res = await db.getStock(int.parse(data.productID);
print(res);

Upvotes: 0

Views: 459

Answers (2)

dshukertjr
dshukertjr

Reputation: 18593

You have to await for the future in order to unwrap the value. You can use a future builder to do this.

Instead of having this:

_infoRow('Currrent Stock', db.getStock(int.parse(data.productID))),

Have this:

FutureBuilder(
    future: db.getStock(int.parse(data.productID),
    builder: (context, snapshot) => _infoRow('Currrent Stock', snapshot.data),
),

Your complete code will look like this:

child: StreamBuilder<Product>(
       initialData: barcode,
       stream: bloc.scannedCode,
       builder: (BuildContext context, AsyncSnapshot snapshot){
         if (snapshot.hasError) return Text('Error: ${snapshot.error}');
        switch (snapshot.connectionState) {
          case ConnectionState.none:
            return Text('Select lot');
          case ConnectionState.waiting:
            return _buildProductInfo(snapshot.data);
          case ConnectionState.active:
          case ConnectionState.done:
            return _buildProductInfo(snapshot.data);
        }
       },
     )

Widget _buildProductInfo(Product data){
    return Container(
      child: ListView(
        padding: EdgeInsets.all(8.0),
        children: <Widget>[
           _infoRow('Product ID', data.name),
           _infoRow('Product Name', data.productID),
           _infoRow('Cost Price', data.costPrice),
           _infoRow('Selling Price', data.salePrice),
           _infoRow('CategoryID', data.categoryID),
           FutureBuilder(
               future: db.getStock(int.parse(data.productID),
               builder: (context, snapshot) => _infoRow('Currrent Stock', snapshot.data),
           )
        ],
      ),
    );
  }

Upvotes: 1

Rubens Melo
Rubens Melo

Reputation: 3305

You have to use async on your _buildProductInfo() method and use await before db.getStock(int.parse(data.productID)) . This way, the execution is suspended until the Future completes.

Upvotes: 0

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