How to pass variable content to a parameter value in dart/flutter? - oop

Question

I may be missing something obvious, but I'm having trouble passing a variable to a parameter or widget in flutter/dart. For example, let's say I have some variable:
String col = 'red';
and I want to pass this to a color parameter to get the equivalent of
color: Colors.red
The difficult thing is that any way I try to pass the value ends up passing a string (which isn't accepted), including trying to pass just the value of col directly or trying to build a function that returns Colors.col.
I think what I need is something like a function like
setColor(String str) {
return Colors.str;
}
but, as you might expect, this returns "The getter 'str' isn't defined for the type 'Colors'." (And similarly for:
setColor(String str) {
return Colors.$str;
}
I know one option is to create a function using a bunch of if's, like
setColor(String str) {
if (str==red) return Colors.red;
if (str==blue) return Colors.blue;
if (str==green) return Colors.green;
etc.
}
but I'd prefer a more elegant option if one is available.
EDIT: It looks like this isn't quite as easy as I'd hoped (see answers and comments to answers below).

Answer 1

The library Supercharged is your best solution. You can try it this way (Hex text or HTML color):
"#ff00ff".toColor(); // pink
"ff0000".toColor(); // red
"00f".toColor(); // blue
"red".toColor(); // red (HTML color name)
"deeppink".toColor(); // deep pink (HTML color name)
Of course, this function depends on extension. Extension methods, introduced in Dart 2.7.
Edit:
extension MainAxisAlignmentExtension on String {
MainAxisAlignment get mainAxis {
switch (this.toUpperCase()) {
case "BETWEEN":
return MainAxisAlignment.spaceBetween;
case "AROUND":
return MainAxisAlignment.spaceAround;
case "EVENLY":
return MainAxisAlignment.spaceEvenly;
case "CENTER":
return MainAxisAlignment.center;
case "START":
return MainAxisAlignment.start;
case "END":
return MainAxisAlignment.end;
default:
return MainAxisAlignment.start;
}
}
}
print("Between".mainAxis);
print("AROUND".mainAxis);

Answer 2

Instead of passing Color as String, you can use type Color
Color col = Colors.red;
If you want to continue using String to store color you can use the hex value
String col = "#FF5733";
And use a function to convert it to color
Color hexToColor(String code) {
return new Color(int.parse(code.substring(1, 7), radix: 16) + 0xFF000000);
}
Example:
Color newColor = hexToColor(col);
Hope this is what you are looking for!

Answer 3

You can pass colors from one widget to another by declaring color as a variable.
final Color redColor=Colors.red;
Then you can pass it to a widget as an argument (Passing color to a widget):
Widget something(Color redColor){
Text("It Works!",style: TextStyle(color: redColor))
}
If you want to pass it from one stateless or stateful widget to another:
class DetailScreen extends StatelessWidget {
// Declare a field that holds the color.
final Color redColor;
// In the constructor, require a Color.
DetailScreen({Key key, #required this.redColor}) : super(key: key);
// Your widget build and other things here
}
Then get the value by calling:
Text("It Works!",style: TextStyle(color: widget.redColor))