CODEWITHSUNDEEP
flutter
Raghav Joshi
Raghav Joshi

Reputation: 177

How to pre-define propeties in classes Flutter

I have created a CardText as a stateless widget and I will use it whenever I would be needing it. But I have a problem. As y'all can see, there are properties that I haven't marked as @required. What I want is these properties have a pre-defined value. Like, suppose the color property, it should be 0xFFFFFFFF until and unless I want somewhere to be as 0xFF000000. But these are final properties that can't be assigned on the basis of ??= method. Yes, I know, marking these properties as @required will require me to define each and every property whenever I call it. But having a pre-defined value will help me a lot to save time and a few lines of code. Well, any expert out there, I don't know how to express the problem, so feel free to change the title. Thank you.

import 'package:flutter/material.dart';
import 'package:google_fonts/google_fonts.dart';

class CardText extends StatelessWidget {
  final String data;
  final int color;
  final int fontSize;
  final FontWeight fontWeight;
  const CardText(
    this.data, {
    this.color,
    this.fontSize,
    this.fontWeight,
  });


  @override
  Widget build(BuildContext context) {
    return Text(
      data,
      style: GoogleFonts.openSans(
        textStyle: TextStyle(
          fontSize: fontSize,
          fontWeight: fontWeight,
          color: Color(color),
        ),
      ),
    );
  }
}

Upvotes: 0

Views: 172

Answers (2)

Jasurbek
Jasurbek

Reputation: 2966

If your arguments are optional then you can give default it right away, like following

const CardText({
    this.data, 
    this.color = 0xFFFFFFFF,
    this.fontSize = 14,
    this.fontWeight,
  })

Upvotes: 1

Banana
Banana

Reputation: 2533

You can use the : colon syntax:

const CardText(
    this.data, {
    this.color,
    this.fontSize,
    this.fontWeight,
  }) : color = 0xFFFFFFFF, data = "data"

The code after the colon will be executed before the code inside the curly brackets. From the linked question

The part after : is called "initializer list. It is a ,-separated list of expressions that can access constructor parameters and can assign to instance fields, even final instance fields. This is handy to initialize final fields with calculated values.

Upvotes: 1

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