Trying to create a switchListTile without DRY in flutter

Question

I am completely new to flutter and I am trying to make an application that has 7 switches for each day of the week.

The problem is resolved when a create 7 different switchlisttile with different values for each one.

But when I extracted the method, the switches don't work.

here is the code below:

Column(
  children: <Widget>[
    buildSwitchListTile(Title : "Monday" , Value : Value1),
    buildSwitchListTile(Title : "Tuesday" , Value : Value2),
    buildSwitchListTile(Title : "Wednesday" , Value :  Value3),
    buildSwitchListTile(Title : "Thursday" , Value : Value4),
    buildSwitchListTile(Title : "Friday" , Value : Value5),
    buildSwitchListTile(Title : "Saturday" , Value : Value6),
    buildSwitchListTile(Title : "Sunday" , Value : Value7),
  ],
),

The extracted method:

SwitchListTile buildSwitchListTile({String Title , bool Value}) {
  return SwitchListTile(
    title: Text(Title),
    value: Value1,
    onChanged: (bool value) => setState(() {
      Value1 = value;
    }),
  );
}

However I am aware that I have used Value1 in the method above, the reason is without it the switches don't work.

Solution 1

The problem is that the Value1 you pass into the method is not the same variable as the Value that the method receives. They have the same value, but if you reassign a value to Value, that will not affect the value of Value1. You can instead hard-code Value1 like you are doing, but that would mean you need a method for each value variable you have, which is not very DRY.

Instead, pass a callback method in for the buildSwitchListTile to call when the tile gets tapped. That way, when you are calling that method in your build method, you can specify which variable each one will change. After that, the program should run just fine.

SwitchListTile buildSwitchListTile({
  String Title, 
  bool Value,
  void Function(bool) onChanged,
}) {
  return SwitchListTile(
    title: Text(Title),
    value: Value,
    onChanged: onChanged,
 );
}

And use it like this:

Column(
  children: <Widget>[
    buildSwitchListTile(Title: "Monday", Value: Value1, 
      onChanged: (val) => setState(() => Value1 = val)),
    buildSwitchListTile(Title: "Tuesday", Value: Value2, 
      onChanged: (val) => setState(() => Value2 = val)),
    buildSwitchListTile(Title: "Wednesday", Value:  Value3, 
      onChanged: (val) => setState(() => Value3 = val)),
    buildSwitchListTile(Title: "Thursday", Value: Value4, 
      onChanged: (val) => setState(() => Value4 = val)),
    buildSwitchListTile(Title: "Friday", Value: Value5, 
      onChanged: (val) => setState(() => Value5 = val)),
    buildSwitchListTile(Title: "Saturday", Value: Value6, 
      onChanged: (val) => setState(() => Value6 = val)),
    buildSwitchListTile(Title: "Sunday", Value: Value7, 
      onChanged: (val) => setState(() => Value7 = val)),
  ],
),

Solution 2

You pass Value1 into the value parameter in the SwitchListTile. Replace that with the value parameter in the buildSwitchListTile method.

Your IDE could probably tell you that the Value parameter is never used.

P.S. parameters and variables use lowerCamelCase. Leaning and sticking to Dart capitalization rules helps everyone understand your code better.