Flutter Instance member ‘result’ can’t be accessed using static access

Question

Please go easy on me, this is my first time using flutter/dart (a couple days in), and is my first time learning a language, I'm not fully understanding of classes and functions...

Basically I have created an app that calculates the diameter of a circle from three x,y points and outputs the circle center coord's and the diameter of the circle. I had it working in one main.dart file, but it was messy, and I will be calculating lots of other things, some using this set of equations for the circle data for further calculations.

I have created a class in another file (calculator.dart) called 'CalcCCenter' here and imported that to main.dart:

import 'package:scidart/numdart.dart';

class CalcCCenter {
  double x1;
  double y1;
  double x2;
  double y2;
  double x3;
  double y3;
  double cX;
  double cY;
  double cDiameter;

  CalcCCenter(
      {this.x1,
      this.y1,
      this.x2,
      this.y2,
      this.x3,
      this.y3,
      this.cX,
      this.cY,
      this.cDiameter}) {
    double a = x1 * (y2 - y3) - y1 * (x2 - x3) + x2 * y3 - x3 * y2;

    double b = (x1 * x1 + y1 * y1) * (y3 - y2) +
        (x2 * x2 + y2 * y2) * (y1 - y3) +
        (x3 * x3 + y3 * y3) * (y2 - y1);

    double c = (x1 * x1 + y1 * y1) * (x2 - x3) +
        (x2 * x2 + y2 * y2) * (x3 - x1) +
        (x3 * x3 + y3 * y3) * (x1 - x2);
    cX = -b / (2 * a);
    cY = -c / (2 * a);

    print('Circle center X $cX');
    print('Circle center y $cY');

    cDiameter = ((hypotenuse(cX - x1, cY - y1)) * 2);
    print('Circle diameter $cDiameter');
  }
}

In main.dart I have this:

onPressed: () {
                      setState(
                        () {
                          double x1 = double.parse(num1controller.text);
                          double y1 = double.parse(num2controller.text);
                          double x2 = double.parse(num3controller.text);
                          double y2 = double.parse(num4controller.text);
                          double x3 = double.parse(num5controller.text);
                          double y3 = double.parse(num6controller.text);
                         

                          CalcCCenter(
                            x1: x1,
                            y1: y1,
                            x2: x2,
                            y2: y2,
                            x3: x3,
                            y3: y3,
                          );

                          //some code here to bring the values from calulator.dart

                        },
                      );
                    },

The inputs from the app are working correctly, the class 'CalcCCenter' in calulator.dart are taking the values and printing them (from calculator.dart). I just need to bring them (cX, cY and Cdiameter) back into main.dart to use. How would I do this with a function? I have tried a few things, but keep getting the error "Flutter Instance member ‘result’ can’t be accessed using static access". Sorry if this may seem basic to many, but I'm just starting out.

Solution

You can call a function that returns a list with the calculated values and not calculate everything inside the constructor.

Example code:

class CalcCCenter {

  List calculate({double x1, double y1, double x2, double y2, double x3, double y3}) {
    double a = x1 * (y2 - y3) - y1 * (x2 - x3) + x2 * y3 - x3 * y2;

    double b = (x1 * x1 + y1 * y1) * (y3 - y2) +
        (x2 * x2 + y2 * y2) * (y1 - y3) +
        (x3 * x3 + y3 * y3) * (y2 - y1);

    double c = (x1 * x1 + y1 * y1) * (x2 - x3) +
        (x2 * x2 + y2 * y2) * (x3 - x1) +
        (x3 * x3 + y3 * y3) * (x1 - x2);
    double cX = -b / (2 * a);
    double cY = -c / (2 * a);
    
    double cDiameter = ((hypotenuse(cX - x1, cY - y1)) * 2);
    
    print('Circle diameter $cDiameter');
    print('Circle center X $cX');
    print('Circle center y $cY');

    return [cX, cY, cDiameter];
  }
}

Then in your 'onPressed' method call it like this:

onPressed: () {
                      setState(
                        () {
                          double x1 = double.parse(num1controller.text);
                          double y1 = double.parse(num2controller.text);
                          double x2 = double.parse(num3controller.text);
                          double y2 = double.parse(num4controller.text);
                          double x3 = double.parse(num5controller.text);
                          double y3 = double.parse(num6controller.text);
                         

                           List result = CalcCCenter().calculate(x1: x1, y1: y1, x2: x2, y2: y2, x3: x3, y3: y3);                

                          // Now you can access the calculated values
                          print('cX: ${result[0]}');
                          print('cY: ${result[1]}');
                          print('cDiameter: ${result[2]}');

                        },
                      );
                    },

Comments

[David Vanstone]

Brilliant, thank you for that. It all makes sense now! Will give it a try after work.

[Luis Cruz]

If it works, don't forget to accept the answer as correct.