是否将最终字段保留在小部件或州？ [英] Keeping final fields on the Widget or the State?

问题描述

应该在哪里保留最终值？

Where should one keep final values?

在 StatefulWidget （当然是我的子类）实例和访问中从 State （子类）通过 widget.thatFinalField 或

In the StatefulWidget (my subclass of course) instance and access it from the State (subclass) via widget.thatFinalField, or

位于州本身。我已经看过这两种方法。每种方法都有利弊吗？

In the State itself. I've seen both approaches already.. Any pros and cons for each of them?

推荐答案

您应该存储<$ c $在 StatefulWidget 上的c> final 成员字段（通过构造函数参数传递），并将其公开。

You should store final member fields (which are passed via constructor arguments) on the StatefulWidget and make them public.

与 StatefulWidget 关联的 State 应该仅使用默认构造函数（无参数），并且其成员字段应该是私有的（以 _ 开头）并且是可变的。内联或在需要昂贵或异步工作的 initState 中初始化它们。

The StatefulWidget's associated State should use only the default constructor (no arguments), and its member fields should be private (starting with a _) and mutable. Initialize them inline or in initState if expensive or async work is necessary.

此模式允许 StatefulWidget 将在其父级调用 setState 时使用新的构造函数参数重新创建/重建，同时重新使用以前的状态，并使其值存储在其可变成员字段中。

This pattern allows the StatefulWidget to be recreated/rebuilt with new constructor arguments when its parents call setState, while re-using the previous State and letting it keep the values stored in its mutable member fields.

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