如何在Dart中为现有类添加构造函数

Question

我想为一些常见的UI类制作一些方便的/工厂构造函数。例如，TextStyle:

enum Font {
AvenirNext,
AvenirNextCondensed
}
enum Weight {
Regular,
Medium,
DemiBold,
Bold
}
// Use:
// TextStyle(Fonts.AvenirNext, Weight.Medium, 20, Colors.white)
// Maybe it can be even shorter?
// TextStyle(AvenirNext, Medium, 20, Colors.black)

在达特怎么办？

Answer 1

像下面的一样扩展TextStyle怎么样

class Font {
static const AvenirNext = 'AvenirNext';
static const AvenirNextCondensed = 'AvenirNextCondensed';
}
class Weight{
static const Regular = FontWeight.w400;
static const Medium = FontWeight.w500;
static const DemiBold = FontWeight.w700;
static const Bold = FontWeight.w900;
}
class CTextStyle extends TextStyle {
CTextStyle(String f, FontWeight w, num s, Color c)
: super(
fontFamily: f,
fontWeight: w,
fontSize: s.toDouble(),
color: c);
}
}

用法：

TextStyle myCustom = CTextStyle(Font.AvenirNext, Weight.Medium, 20, Colors.black);