useState

Description: 在compose中使用state需要写一点模板代码，虽然谈不上有多麻烦，但是还是能简化一下的； 返回值是MutableState，可以解构后使用。如果是可空对象需要显示声明：

val (state,setState) = useState<Boolean?>(null)
val otherState by useState("")

这样做还有一个好处就是减少闭包层级，我们可以轻松的构造一些简单的受控组件：

val (state, setState) = useState("")
OutlinedTextField(
    value = name,
    onValueChange = setState,
    label = { Text("Name") }
)

重要提示：这种方式在便捷的同时也有俩个缺陷：

1. 带来闭包问题，当我们在某个闭包函数中使用状态，会出现闭包问题，需要使用useLatestRef避免。

2. 当你快速的（毫秒级）调用set函数时，会触发 Compose 的重组优化，导致状态丢失。

这种情况下，可以退回到使用 by 委托来获取状态对象

Important note: While this method is convenient, it also has two flaws:

1. It causes closure problems. When we use state in a closure function, closure problems will occur, need to use useLatestRef to avoid.

2. When you call the set function quickly(millisecond level), Compose's recompose optimization will be triggered, resulting in state loss.

In this case, you can fall back to using the by delegate to get the state object

用于方便的创建派生状态，派生状态不同于普通的MutableState，他是一个只读的状态， 它只会在依赖发生变化时重新计算改变状态，在其他的框架中也称之为计算属性或者计算状态。

Used to conveniently create derived states. Derived state is different from ordinary MutableState. It is a read-only state. It will only recalculate the changed state when dependencies change. It is also called a Computed Properties in other frameworks.

Parameters