stephanedeluca/main.dart

## readme.md

      
    Raw
  

              readme.md
            
          
    Shokaze Yassine b2

Created with <3 with dartpad.dev.

  
## main.dart
import 'package:flutter/material.dart';

/// The buid number
const _buildNumber = 8;

// lets define the stateless part of the screen (AppBar, app title, background color...)
class MetaDataAdScreen extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
  return MaterialApp(
      debugShowCheckedModeBanner: false,
      theme: ThemeData(useMaterial3: true,
                       colorSchemeSeed: Colors.amber),
      darkTheme: ThemeData(useMaterial3: true, colorSchemeSeed: Colors.amber.shade100),
      themeMode: ThemeMode.light, // Default is system

      title: "product informations",
      home: Scaffold(
        appBar: AppBar(
          title: Text(
            "My vehicle caracteristics form (b$_buildNumber)",
            style: TextStyle(color: Colors.white),
          ),
          centerTitle: true,
          backgroundColor: Colors.red
        ),
        body: ListRowsGenerator(),
      ),
    );
  }
}


/// A generic field widget implemented as a ListTile
/// TODO: I must specilize for all the type I need to support
class FieldInput<T> extends StatelessWidget {
  /// Name of the field
  final String name;
  /// The field to edit
  final Map<String,dynamic> field;

  //T value;
  const FieldInput({
    super.key,
    required this.name,
    required this.field,
  });


  @override String toString({DiagnosticLevel minLevel = DiagnosticLevel.info}) => "FieldInput: $name: ${field['value']}";

  @override Widget build(BuildContext context) {

    /// Providionned icon widget or null
    final icon = field['icon']==null?null:Icon( field['icon']);

    // Returns the lit tile with potential leading icon and triling unit.
    return ListTile(
      leading: icon,
      title: TextFormField(
        initialValue: field['value']?.toString(),
        // == Always fires the validator
        autovalidateMode:AutovalidateMode.always,


        // Provide initialValue of TextFormField the object that sits at key 'value' if and ONLY IF it exists, otherwise provide null. Providing means: call toString() method only if field['value'] is not null
        decoration: InputDecoration(
          labelText: name,
        ),
         keyboardType:

          T is int ?
          TextInputType.number:T is double?

          const TextInputType.numberWithOptions(decimal:true)

          :null
          ,


          /// Called whenever the user strike a key. The current valye (as a string) sits in value (btw, which could be null if nothing was stoke)
          onChanged: (value) {

            field['value'] = value;

            //setStte()

             //debugPrint("Field $name: $value");

            debugPrint("Field is now: $field");
          },
        validator:(value){
          if (value==null || value.isEmpty) return "This field is mandatory";
          if (value.length<4) return 'You must provide at least 4 charcaters';
          return null;
        }
        ),
      trailing:field["unit"] == null ? null: Text(field["unit"]),
    );
  }
}


/// The input field that let the user pick a value from many
//TODO: see how to make EnumInputField shar code with other InputField<T>
class EnumInputField extends StatelessWidget {

  /// The list of the enums To pick from
  final List<String> values;

  /// The call back that is called with the selected value or null if user cancels
  final void Function(String?) onSelected;

  const EnumInputField({super.key, required this.values, required this.onSelected,});

  @override Widget build(BuildContext context) {

    /// We display a scrollin view
    return ListView(
      padding: const EdgeInsets.all(20),
      physics: const BouncingScrollPhysics(),
      children:

      [
        // == With a title
       Text("Pick a value", style:Theme.of(context).textTheme.titleLarge),

        // == A separator (Note that I use a stanard text instead of
        // a metrics, so that everything will stand in shape whatever
        // the the used)
        const Text(""), // const SizedBox(10),

        // == The list of the values themseleves
      ...values.map((v)=>

                           TextButton(onPressed:() {


                             debugPrint("tap on $v");


                             // == Provide the user-seleted value to the parent
                             onSelected(v);

                             // == Just close the bottom sheet
                             Navigator.of(context).pop();
                           },
                           child:Text(v))).toList(),  // Operator `...` explodes a list into individuel items => "a", "b", "c", etc.


      const Text(""),
        TextButton(onPressed:(){

           // == Tell parent user's cancelled
           onSelected(null);

                     // == Just close the bottom sheet
           Navigator.of(context).pop();


        }, child:Text("Cancel")),
      ]
    );
  }

}

/*
/// The form definition from the server
final definition = {
  "age": {
    "type": "int",
  }
};

/// Once the user filled in, we get:
final definition = {
  "age": {
    "type": "int",
    "value": 43,      // What the user filled in!
  }
};
*/

/*
/// A person model
class Person extends Object {
  /// The person's firstname
  final String name;

  /// The Weight of the person
  final double? weight;

  /// The ID of the instance
  late final _id; // private


  Person({required this.name, this.weight}) {
    // TODO: Computes a statisically unique ID
    // FIXME: This bug is referred to as http://atlassian.com/342432ZERZERZ
    _id = "12";
  }


  @override String toString() =>
      'Person "name" weights ${weight}Kg';
 // Replaces [instane@12432ZERZZERZER] of Person] by Person "Yassine" weights 80Kg]
}

/// The large person (aka over 200lbs)
/// My new class is LArge Person and I reach any of its memeber via `this`.
/// As it extends Person, you can reach any accessible from PErson via `super`.
class LargePerson extends Person {
  /// Create instances of larg person, with default name as Demis Roussos
  LargePerson.withDefault({super.name="Demis Roussos", super.weight});

  /// Create intances of large person, with sealed name to Demis Roussos
  LargePerson.onlyWeight({super.weight}):super(name:"Demis Roussos");
}

final g = LargePerson.withDefault(weight:250); //Kg
final h = LargePerson.withDefault(name:"toto", weight:250);
final i = LargePerson.onlyWeight(weight:230);
//final j = LargePerson.onlyWeight(name:"toto", weight:250);// Could not provide name


/// The widget that draws the user's profile
class YassineProfile extends StatelessWidget {
  /// The person's name to display
  final String name;

  const YassineProfile({super.key, required this.name});

  @override Widget build(BuildContext context) {
    return Text("Name: $name");
  }

}

void explainingHowTypesWork() {
  /// TextFormField: A (Text) form field => String
  dynamic s = "Hello";
  s = 12;

  // Molded object (instance) : mold (class)
  s = YassineProfile(name:"Yassine");


  final yassine = Person(name:"Yassine");
  s = yassine;

  s = null;

  //Map<dynamic, dynamic> s1;
  //Map<int,String> s2;
  //Map<Widget,double> s3;

  Map<String, dynamic> dict = {
    "age": 12, // int
    "weight": 82.3, // double
    "fistname": "Yassine", // String
    "definition": { // Map<String, dynamic>
      "type": "int",
      "value": 12,
    },
  };

  dict["int"] = 123;


  // blah blah

  final v = dict["definition"]; // could be null if something gone wrong

  if (v is Map<String, dynamic>) { // Make sure v is of the expected type, aka. mateches specs, hourray!
    //TODO:
  }
  // ==
  else {
    throw Exception("Error: Form definiton is wrong: expecting Map>String, dynamic> but got $v");
  }


  final s0 = "Hello $v"; //==> s0 = "Hello "+v.toString()+"";
}

/// Reads the form definition the server just sent to us. Warning could rethrow whenever something goes wrong.
void readFormDefinitionFromServer() {

  /// The stream I use to update blah blah
  //late final stream;
  // Run the reader
  try {
    //stream = Stream();

    explainingHowTypesWork();
  }
  catch(e) {
    rethrow;
  }
  /// Finally is the code that is runf whatever the branches the code took: eitheir try or catch.
  finally {
    //stream.dispose();
    debugPrint("Leaving readFormDefinitonFromServer()");
  }
}
*/
//let's create a class that take as input the the CategoryCarMetaData Map and return a listView widget containing in each line
//a represetation of each element of  CategoryCarMetaData.

class ListRowsGenerator extends StatefulWidget{
  @override
  State<StatefulWidget> createState() =>ListListRowsGeneratorState();
}
class ListListRowsGeneratorState extends State {
  String ? valueChosen;

  @override
  Widget build(BuildContext context) {
    final fields = getCategoryCarMetaData();

    //final k = fields.keys.first;
    //return FieldInput(name: k, field: fields[k]);


    // == Selet the right Inputfiel generic according to the fiel type
    final widgets = fields.keys.map<Widget>((k) {

      debugPrint("field $k…");

      /// A shortcut on field k
      final f = fields[k];
      debugPrint("field $k: type is ${f["type"]}");


          switch(f["type"]) {
          case "int": return FieldInput<int>(name: k, field: f);

            case "enum":

              assert(f["values"] is Set<String>,"field values is not a set of string");
              assert(f["values"]!=null, "field values is null");
              assert(f["values"].length>1,"field values is one length");


              debugPrint("field values: ${f["values"]}");


              return ListTile(
                title:Text(k),
                subtitle:f["value"]==null?null:Text(f["value"]),
                trailing:
               TextButton(onPressed:() {

                  showModalBottomSheet(context:context, builder:(context)=>

               EnumInputField(
                 values: f["values"].toList(),
                 onSelected:(value) {

                   setState((){
                     debugPrint('f["value"]=${f["value"]}');
                     debugPrint('f["value"] set to $value');
                     f["value"] = value;
                   });
                 },
               ),
             );
           },
           child: const Icon(Icons.edit)),
          );
          default: return FieldInput(name: k,field: f);
         }
      }
    ).toList();

    //debugPrint("Field widgets: $widgets");


    final w= EnumInputField(values:const ["A","b","c","d","e","f","g","h"],onSelected:(value){

      //TODO: make something useful of user-picked value

      // == User's cancelled? do nothing
      if (value==null) return;

      // == Store the value the user picked to the form
      debugPrint("User picked $value");

      setState((){
        //field["value"]=value;
      });

    });

    return

      Column(
      mainAxisSize: MainAxisSize.min,
      children:[


      ListView(
        physics: const BouncingScrollPhysics(),
        shrinkWrap:true,
        children: widgets,
      ),


        // == Allow the user to pick from an enum
                ElevatedButton(onPressed:() {

                  showModalBottomSheet(context:context, builder:(context)=>w);


                },child:Text("Pick a letter")),

       ])
        ;

   /*
   List <Widget>ListViewRows=[]; //empty list of widgets that will contain the listview elements


    for (String key in getCategoryCarMetaData().keys){ //for loop to navigate the CategoryCarMetaData and extract data and put it as widget in the ListViewRows
      switch (getCategoryCarMetaData()[key]["type"]){ //depending on type of data, widget that represent it is different
        case "enum": {  //if the type is enum, we will use DropDownButton to display all values allowed so the customer can choose.

             final List itemsList=getCategoryCarMetaData()[key]["values"].toList();
             ListViewRows.add(Center(child: Text(key)));
             ListViewRows.add(DropdownButton<String>( value: valueChosen,
                                                      isExpanded: true,
                                                      onChanged: (String ?newValue){setState(() {valueChosen=newValue;});},
                                                      items : itemsList.map((e) =>DropdownMenuItem<String>(
                                                                    value: e,
                                                                    child: Text(e))).toList()));
        } break;
        case "string": { //if the type is String, we will use a TextFormField to let the user Add values with keyboard
             ListViewRows.add(Center(child: Text(key)));
             ListViewRows.add(TextFormField());
        } break;
        case "date": { //if the type is enum, we will use a TextFormField to Add Date Value
             ListViewRows.add(Center(child: Text(key)));
             ListViewRows.add(TextFormField());
        } break;
        case "int": { //if the type is int, we will use a TextFormField to Add this Value
             ListViewRows.add(Center(child: Text(key)));
             ListViewRows.add(TextFormField());
        } break;
        case "double": { //if the type is int, we will use a TextFormField to Add this Value
             ListViewRows.add(Center(child: Text(key)));
             ListViewRows.add(TextFormField());
        } break;

        default: {
             ListViewRows.add(Center(child: Text(key)));
             ListViewRows.add(TextFormField());
        }
        break;

      }
    }

  return(ListView(

    padding: const EdgeInsets.all(20),
    children: ListViewRows));
    */
  }

}

/// Get the meta data for the `car` category
Map<String, dynamic> getCategoryCarMetaData() {
 const energies = {
          "icon": Icons.energy_savings_leaf,
          "type": "enum",
          "values": {
              "electric",
              "hybrid",
              "reloaded hybrid",
              "diesel",
              "gas",
              "hydrogen",
              "gpl",
              "lng",
              "other"
            },
        };
  const brands = {
          "icon": Icons.branding_watermark,
          "type": "enum",
          "values": {
              "mercedes-benz",
              "bmw",
              "renault",
              "citroën",
              "peugeot",
              "opel",
              "vw",
              "simca",
              "ford",
              "gm",
              "cadillac",
              "other"
            },
        };

  const types = {
          "icon": Icons.type_specimen,
          "type": "enum",
          "values": {"sedan", "suv", "pickup", "truck", "semitruck", "other"},
        };
  return {
          "type": types,
          "energy": energies,
          "brand": brands,
          "model": {"type": "string"},
          "date": {
            "icon": Icons.calendar_today,
            "type": "date",
          },
          "power": {"icon": Icons.power, "type": "int", "unit": "CV", "value": 12,}
        };
}

/* DropDown Button Template
string ? valueChosen;
final List valueChosen=["tap1","tap2","tap3"];
DropdownButton<String>( value: valueChosen,
                        onChanged: (newValue){setState(() {valueChosen=newValue;});},
                        items : itemsList.map((e) =>DropdownMenuItem<String>(value: e,
                                                                             child: Text(e))).toList())
*/


/*
Intro
It's about creating a simple application, which allows a user to feed a form allowing him to create the description data relating to the car he wants to sell 🚗 .
The information will be returned to elastic search from the application.Then you'll build a screen allowing him to build a search filter, run it, and finally display the results on the screen. He can then tap on it to view all the data.
The peculiarity here is that the form is not known in advance: it will be downloaded from a remote server: outside the scope of this work, you will hard code the description in the code meanwhile as I show in the wiki .

You are asked to deliver:
Step 1: Create ClassifiedAdMetaDataFormScreen screen that takes the category metadata from a Map<String, dynamic> and presents the related form built on the fly;
Step 2: Make the final evolution of the previous screen that also stores the data in the Firestore collection testClassifiedAd.
Step 3: Create ClassifiedAdSearchEngineScreen screen that enable the user to build a filter interactively according to the category metadata;
Step 4: Make the final evolution of the previous screen to actually build and run the request from the generated filter and create the ClassifiedAdSearchEngineResultsScreen screen that displays the results.
Have fun!

for the solution explanation go to : README.md

*/


void main() {
  runApp(  MetaDataAdScreen());
}
	import 'package:flutter/material.dart';

	/// The buid number
	const _buildNumber = 8;

	// lets define the stateless part of the screen (AppBar, app title, background color...)
	class MetaDataAdScreen extends StatelessWidget {
	@override
	Widget build(BuildContext context) {
	return MaterialApp(
	debugShowCheckedModeBanner: false,
	theme: ThemeData(useMaterial3: true,
	colorSchemeSeed: Colors.amber),
	darkTheme: ThemeData(useMaterial3: true, colorSchemeSeed: Colors.amber.shade100),
	themeMode: ThemeMode.light, // Default is system

	title: "product informations",
	home: Scaffold(
	appBar: AppBar(
	title: Text(
	"My vehicle caracteristics form (b$_buildNumber)",
	style: TextStyle(color: Colors.white),
	),
	centerTitle: true,
	backgroundColor: Colors.red
	),
	body: ListRowsGenerator(),
	),
	);
	}
	}


	/// A generic field widget implemented as a ListTile
	/// TODO: I must specilize for all the type I need to support
	class FieldInput<T> extends StatelessWidget {
	/// Name of the field
	final String name;
	/// The field to edit
	final Map<String,dynamic> field;

	//T value;
	const FieldInput({
	super.key,
	required this.name,
	required this.field,
	});


	@override String toString({DiagnosticLevel minLevel = DiagnosticLevel.info}) => "FieldInput: $name: ${field['value']}";

	@override Widget build(BuildContext context) {

	/// Providionned icon widget or null
	final icon = field['icon']==null?null:Icon( field['icon']);

	// Returns the lit tile with potential leading icon and triling unit.
	return ListTile(
	leading: icon,
	title: TextFormField(
	initialValue: field['value']?.toString(),
	// == Always fires the validator
	autovalidateMode:AutovalidateMode.always,


	// Provide initialValue of TextFormField the object that sits at key 'value' if and ONLY IF it exists, otherwise provide null. Providing means: call toString() method only if field['value'] is not null
	decoration: InputDecoration(
	labelText: name,
	),
	keyboardType:

	T is int ?
	TextInputType.number:T is double?

	const TextInputType.numberWithOptions(decimal:true)

	:null
	,



	/// Called whenever the user strike a key. The current valye (as a string) sits in value (btw, which could be null if nothing was stoke)
	onChanged: (value) {

	field['value'] = value;

	//setStte()

	//debugPrint("Field $name: $value");

	debugPrint("Field is now: $field");
	},
	validator:(value){
	if (value==null \|\| value.isEmpty) return "This field is mandatory";
	if (value.length<4) return 'You must provide at least 4 charcaters';
	return null;
	}
	),
	trailing:field["unit"] == null ? null: Text(field["unit"]),
	);
	}
	}



	/// The input field that let the user pick a value from many
	//TODO: see how to make EnumInputField shar code with other InputField<T>
	class EnumInputField extends StatelessWidget {

	/// The list of the enums To pick from
	final List<String> values;

	/// The call back that is called with the selected value or null if user cancels
	final void Function(String?) onSelected;

	const EnumInputField({super.key, required this.values, required this.onSelected,});

	@override Widget build(BuildContext context) {

	/// We display a scrollin view
	return ListView(
	padding: const EdgeInsets.all(20),
	physics: const BouncingScrollPhysics(),
	children:

	[
	// == With a title
	Text("Pick a value", style:Theme.of(context).textTheme.titleLarge),

	// == A separator (Note that I use a stanard text instead of
	// a metrics, so that everything will stand in shape whatever
	// the the used)
	const Text(""), // const SizedBox(10),

	// == The list of the values themseleves
	...values.map((v)=>

	TextButton(onPressed:() {


	debugPrint("tap on $v");


	// == Provide the user-seleted value to the parent
	onSelected(v);

	// == Just close the bottom sheet
	Navigator.of(context).pop();
	},
	child:Text(v))).toList(), // Operator `...` explodes a list into individuel items => "a", "b", "c", etc.


	const Text(""),
	TextButton(onPressed:(){

	// == Tell parent user's cancelled
	onSelected(null);

	// == Just close the bottom sheet
	Navigator.of(context).pop();


	}, child:Text("Cancel")),
	]
	);
	}

	}

	/*
	/// The form definition from the server
	final definition = {
	"age": {
	"type": "int",
	}
	};

	/// Once the user filled in, we get:
	final definition = {
	"age": {
	"type": "int",
	"value": 43, // What the user filled in!
	}
	};
	*/

	/*
	/// A person model
	class Person extends Object {
	/// The person's firstname
	final String name;

	/// The Weight of the person
	final double? weight;

	/// The ID of the instance
	late final _id; // private


	Person({required this.name, this.weight}) {
	// TODO: Computes a statisically unique ID
	// FIXME: This bug is referred to as http://atlassian.com/342432ZERZERZ
	_id = "12";
	}


	@override String toString() =>
	'Person "name" weights ${weight}Kg';
	// Replaces [instane@12432ZERZZERZER] of Person] by Person "Yassine" weights 80Kg]
	}

	/// The large person (aka over 200lbs)
	/// My new class is LArge Person and I reach any of its memeber via `this`.
	/// As it extends Person, you can reach any accessible from PErson via `super`.
	class LargePerson extends Person {
	/// Create instances of larg person, with default name as Demis Roussos
	LargePerson.withDefault({super.name="Demis Roussos", super.weight});

	/// Create intances of large person, with sealed name to Demis Roussos
	LargePerson.onlyWeight({super.weight}):super(name:"Demis Roussos");
	}

	final g = LargePerson.withDefault(weight:250); //Kg
	final h = LargePerson.withDefault(name:"toto", weight:250);
	final i = LargePerson.onlyWeight(weight:230);
	//final j = LargePerson.onlyWeight(name:"toto", weight:250);// Could not provide name



	/// The widget that draws the user's profile
	class YassineProfile extends StatelessWidget {
	/// The person's name to display
	final String name;

	const YassineProfile({super.key, required this.name});

	@override Widget build(BuildContext context) {
	return Text("Name: $name");
	}

	}

	void explainingHowTypesWork() {
	/// TextFormField: A (Text) form field => String
	dynamic s = "Hello";
	s = 12;

	// Molded object (instance) : mold (class)
	s = YassineProfile(name:"Yassine");


	final yassine = Person(name:"Yassine");
	s = yassine;

	s = null;

	//Map<dynamic, dynamic> s1;
	//Map<int,String> s2;
	//Map<Widget,double> s3;

	Map<String, dynamic> dict = {
	"age": 12, // int
	"weight": 82.3, // double
	"fistname": "Yassine", // String
	"definition": { // Map<String, dynamic>
	"type": "int",
	"value": 12,
	},
	};

	dict["int"] = 123;


	// blah blah

	final v = dict["definition"]; // could be null if something gone wrong

	if (v is Map<String, dynamic>) { // Make sure v is of the expected type, aka. mateches specs, hourray!
	//TODO:
	}
	// ==
	else {
	throw Exception("Error: Form definiton is wrong: expecting Map>String, dynamic> but got $v");
	}


	final s0 = "Hello $v"; //==> s0 = "Hello "+v.toString()+"";
	}

	/// Reads the form definition the server just sent to us. Warning could rethrow whenever something goes wrong.
	void readFormDefinitionFromServer() {

	/// The stream I use to update blah blah
	//late final stream;
	// Run the reader
	try {
	//stream = Stream();

	explainingHowTypesWork();
	}
	catch(e) {
	rethrow;
	}
	/// Finally is the code that is runf whatever the branches the code took: eitheir try or catch.
	finally {
	//stream.dispose();
	debugPrint("Leaving readFormDefinitonFromServer()");
	}
	}
	*/
	//let's create a class that take as input the the CategoryCarMetaData Map and return a listView widget containing in each line
	//a represetation of each element of CategoryCarMetaData.

	class ListRowsGenerator extends StatefulWidget{
	@override
	State<StatefulWidget> createState() =>ListListRowsGeneratorState();
	}
	class ListListRowsGeneratorState extends State {
	String ? valueChosen;

	@override
	Widget build(BuildContext context) {
	final fields = getCategoryCarMetaData();

	//final k = fields.keys.first;
	//return FieldInput(name: k, field: fields[k]);



	// == Selet the right Inputfiel generic according to the fiel type
	final widgets = fields.keys.map<Widget>((k) {

	debugPrint("field $k…");

	/// A shortcut on field k
	final f = fields[k];
	debugPrint("field $k: type is ${f["type"]}");




	switch(f["type"]) {
	case "int": return FieldInput<int>(name: k, field: f);

	case "enum":

	assert(f["values"] is Set<String>,"field values is not a set of string");
	assert(f["values"]!=null, "field values is null");
	assert(f["values"].length>1,"field values is one length");



	debugPrint("field values: ${f["values"]}");



	return ListTile(
	title:Text(k),
	subtitle:f["value"]==null?null:Text(f["value"]),
	trailing:
	TextButton(onPressed:() {

	showModalBottomSheet(context:context, builder:(context)=>

	EnumInputField(
	values: f["values"].toList(),
	onSelected:(value) {

	setState((){
	debugPrint('f["value"]=${f["value"]}');
	debugPrint('f["value"] set to $value');
	f["value"] = value;
	});
	},
	),
	);
	},
	child: const Icon(Icons.edit)),
	);
	default: return FieldInput(name: k,field: f);
	}
	}
	).toList();

	//debugPrint("Field widgets: $widgets");


	final w= EnumInputField(values:const ["A","b","c","d","e","f","g","h"],onSelected:(value){

	//TODO: make something useful of user-picked value

	// == User's cancelled? do nothing
	if (value==null) return;

	// == Store the value the user picked to the form
	debugPrint("User picked $value");

	setState((){
	//field["value"]=value;
	});

	});

	return

	Column(
	mainAxisSize: MainAxisSize.min,
	children:[



	ListView(
	physics: const BouncingScrollPhysics(),
	shrinkWrap:true,
	children: widgets,
	),


	// == Allow the user to pick from an enum
	ElevatedButton(onPressed:() {

	showModalBottomSheet(context:context, builder:(context)=>w);


	},child:Text("Pick a letter")),

	])
	;

	/*
	List <Widget>ListViewRows=[]; //empty list of widgets that will contain the listview elements




	for (String key in getCategoryCarMetaData().keys){ //for loop to navigate the CategoryCarMetaData and extract data and put it as widget in the ListViewRows
	switch (getCategoryCarMetaData()[key]["type"]){ //depending on type of data, widget that represent it is different
	case "enum": { //if the type is enum, we will use DropDownButton to display all values allowed so the customer can choose.

	final List itemsList=getCategoryCarMetaData()[key]["values"].toList();
	ListViewRows.add(Center(child: Text(key)));
	ListViewRows.add(DropdownButton<String>( value: valueChosen,
	isExpanded: true,
	onChanged: (String ?newValue){setState(() {valueChosen=newValue;});},
	items : itemsList.map((e) =>DropdownMenuItem<String>(
	value: e,
	child: Text(e))).toList()));
	} break;
	case "string": { //if the type is String, we will use a TextFormField to let the user Add values with keyboard
	ListViewRows.add(Center(child: Text(key)));
	ListViewRows.add(TextFormField());
	} break;
	case "date": { //if the type is enum, we will use a TextFormField to Add Date Value
	ListViewRows.add(Center(child: Text(key)));
	ListViewRows.add(TextFormField());
	} break;
	case "int": { //if the type is int, we will use a TextFormField to Add this Value
	ListViewRows.add(Center(child: Text(key)));
	ListViewRows.add(TextFormField());
	} break;
	case "double": { //if the type is int, we will use a TextFormField to Add this Value
	ListViewRows.add(Center(child: Text(key)));
	ListViewRows.add(TextFormField());
	} break;

	default: {
	ListViewRows.add(Center(child: Text(key)));
	ListViewRows.add(TextFormField());
	}
	break;

	}
	}

	return(ListView(

	padding: const EdgeInsets.all(20),
	children: ListViewRows));
	*/
	}

	}

	/// Get the meta data for the `car` category
	Map<String, dynamic> getCategoryCarMetaData() {
	const energies = {
	"icon": Icons.energy_savings_leaf,
	"type": "enum",
	"values": {
	"electric",
	"hybrid",
	"reloaded hybrid",
	"diesel",
	"gas",
	"hydrogen",
	"gpl",
	"lng",
	"other"
	},
	};
	const brands = {
	"icon": Icons.branding_watermark,
	"type": "enum",
	"values": {
	"mercedes-benz",
	"bmw",
	"renault",
	"citroën",
	"peugeot",
	"opel",
	"vw",
	"simca",
	"ford",
	"gm",
	"cadillac",
	"other"
	},
	};

	const types = {
	"icon": Icons.type_specimen,
	"type": "enum",
	"values": {"sedan", "suv", "pickup", "truck", "semitruck", "other"},
	};
	return {
	"type": types,
	"energy": energies,
	"brand": brands,
	"model": {"type": "string"},
	"date": {
	"icon": Icons.calendar_today,
	"type": "date",
	},
	"power": {"icon": Icons.power, "type": "int", "unit": "CV", "value": 12,}
	};
	}

	/* DropDown Button Template
	string ? valueChosen;
	final List valueChosen=["tap1","tap2","tap3"];
	DropdownButton<String>( value: valueChosen,
	onChanged: (newValue){setState(() {valueChosen=newValue;});},
	items : itemsList.map((e) =>DropdownMenuItem<String>(value: e,
	child: Text(e))).toList())
	*/




	/*
	Intro
	It's about creating a simple application, which allows a user to feed a form allowing him to create the description data relating to the car he wants to sell 🚗 .
	The information will be returned to elastic search from the application.Then you'll build a screen allowing him to build a search filter, run it, and finally display the results on the screen. He can then tap on it to view all the data.
	The peculiarity here is that the form is not known in advance: it will be downloaded from a remote server: outside the scope of this work, you will hard code the description in the code meanwhile as I show in the wiki .

	You are asked to deliver:
	Step 1: Create ClassifiedAdMetaDataFormScreen screen that takes the category metadata from a Map<String, dynamic> and presents the related form built on the fly;
	Step 2: Make the final evolution of the previous screen that also stores the data in the Firestore collection testClassifiedAd.
	Step 3: Create ClassifiedAdSearchEngineScreen screen that enable the user to build a filter interactively according to the category metadata;
	Step 4: Make the final evolution of the previous screen to actually build and run the request from the generated filter and create the ClassifiedAdSearchEngineResultsScreen screen that displays the results.
	Have fun!

	for the solution explanation go to : README.md

	*/





	void main() {
	runApp( MetaDataAdScreen());
	}