CODEWITHSUNDEEP
dartflutter
tedirgin
tedirgin

Reputation: 43

Dart: Function with String as Parameter as a Parameter in Callback

I'm learning Flutter right now, trying to code a simple calculator. I am building rows using this code:

Row(    // creates row
mainAxisAlignment: MainAxisAlignment.spaceEvenly, //row is spaced evenly
children: <Widget>[
   _button("4", _number("4")), //calls _button widget passing String 4 and function _number, which passes string 4 also
   _button("5", _number("5")), //button with value 5
   _button("6", _number("6")), //button with value 6
   _button("-", _min("null")) //button for subtraction
  ],
),

my _button widget looks like this:

Widget _button(String number, Function() f(String number)){ //parameters: the button value as String and the function with the value as String
  return MaterialButton(
    height: buttonHeight,
    minWidth: buttonHeight,
    child: Text(number,
        style: TextStyle(fontWeight: FontWeight.bold, fontSize: 48.0)),
    textColor: Colors.black,
    color: Colors.grey[100],
    onPressed: f,  //function is called
  );
}

Now I want to pass the String number to the Function f, so when the function _number is called, it takes the String number and pastes it onto the display:

void _number(String number){
  setState(() {
   display=display + number ;
  });
}

It does not work, I tried to solve it, but was not successful. Does anyone have an idea?

Thanks!

Upvotes: 1

Views: 7986

Answers (1)

Juanes30
Juanes30

Reputation: 2556

you have to change this:

Widget _button(String number, Function() f(String number)){ //parameters: the button value as String and the function with the value as String
  return MaterialButton(
    height: buttonHeight,
    minWidth: buttonHeight,
    child: Text(number,
        style: TextStyle(fontWeight: FontWeight.bold, fontSize: 48.0)),
    textColor: Colors.black,
    color: Colors.grey[100],
    onPressed: f,  //function is called
  );

for this:

Widget _button(String number, Function(String number) f){ //parameters: the button value as String and the function with the value as String
  return MaterialButton(
    height: buttonHeight,
    minWidth: buttonHeight,
    child: Text(number,
        style: TextStyle(fontWeight: FontWeight.bold, fontSize: 48.0)),
    textColor: Colors.black,
    color: Colors.grey[100],
    onPressed: () {
       f(number); // function is called
    },  
  );

The main change is that the parameters go inside Function(String param1, String param2) nameFunction which in your case would be Function(String number) f

Upvotes: 3

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