+ 0024 [对象] 一个对象有很多属性时，如何便捷地复制出另一个略有差异对象

[toly1994328]

可以参考Flutter源码，在类中给出一个copyWith的方法。(当然，方法名可以随意)

[toly1994328]

比如MediaQueryData有非常多的属性，如果根据旧对象想得到只是一两条不同的新对象,一点点写会比较麻烦.

  const MediaQueryData({
    this.size = Size.zero,
    this.devicePixelRatio = 1.0,
    this.textScaleFactor = 1.0,
    this.platformBrightness = Brightness.light,
    this.padding = EdgeInsets.zero,
    this.viewInsets = EdgeInsets.zero,
    this.systemGestureInsets = EdgeInsets.zero,
    this.viewPadding = EdgeInsets.zero,
    this.alwaysUse24HourFormat = false,
    this.accessibleNavigation = false,
    this.invertColors = false,
    this.highContrast = false,
    this.disableAnimations = false,
    this.boldText = false,
    this.navigationMode = NavigationMode.traditional,
  })

---

MediaQueryData源码中使用copyWith方便构建新对象。

MediaQueryData copyWith({
  Size size,
  double devicePixelRatio,
  double textScaleFactor,
  Brightness platformBrightness,
  EdgeInsets padding,
  EdgeInsets viewPadding,
  EdgeInsets viewInsets,
  EdgeInsets systemGestureInsets,
  bool alwaysUse24HourFormat,
  bool highContrast,
  bool disableAnimations,
  bool invertColors,
  bool accessibleNavigation,
  bool boldText,
  NavigationMode navigationMode,
}) {
  return MediaQueryData(
    size: size ?? this.size,
    devicePixelRatio: devicePixelRatio ?? this.devicePixelRatio,
    textScaleFactor: textScaleFactor ?? this.textScaleFactor,
    platformBrightness: platformBrightness ?? this.platformBrightness,
    padding: padding ?? this.padding,
    viewPadding: viewPadding ?? this.viewPadding,
    viewInsets: viewInsets ?? this.viewInsets,
    systemGestureInsets: systemGestureInsets ?? this.systemGestureInsets,
    alwaysUse24HourFormat: alwaysUse24HourFormat ?? this.alwaysUse24HourFormat,
    invertColors: invertColors ?? this.invertColors,
    highContrast: highContrast ?? this.highContrast,
    disableAnimations: disableAnimations ?? this.disableAnimations,
    accessibleNavigation: accessibleNavigation ?? this.accessibleNavigation,
    boldText: boldText ?? this.boldText,
    navigationMode: navigationMode ?? this.navigationMode,
  );
}