英文:
Android Jetpack compose, field expose
问题
val removingPluggableScreens: Boolean get() = _removingPluggableScreens.value 与 val removingPluggableScreens: Boolean = _removingPluggableScreens.value 之间的区别在于以下部分：
第一种方式（使用get()）允许您创建一个只读属性，每次访问 removingPluggableScreens 时都会调用 _removingPluggableScreens.value 来获取最新值。这意味着它会在每次访问时动态获取 _removingPluggableScreens.value 的值。
第二种方式（不使用get()）创建了一个简单的只读属性，它在初始化时获取 _removingPluggableScreens.value 的值，然后将其存储在 removingPluggableScreens 中。这意味着 removingPluggableScreens 的值在初始化后不会再随 _removingPluggableScreens.value 的更改而更新。
因此，第一种方式始终提供了最新的 _removingPluggableScreens.value，而第二种方式只提供了初始值。选择哪种方式取决于您的需求，如果需要在每次访问时获取最新值，使用第一种方式更合适。
英文:
I have a question about this code,
private val _removingPluggableScreens = mutableStateOf(false)
val removingPluggableScreens: Boolean get() = _removingPluggableScreens.value
fun updateRemovingPluggableScreens(shouldRemovePluggableScreens: Boolean) {
if (shouldRemovePluggableScreens != _removingPluggableScreens.value) {
_removingPluggableScreens.value = shouldRemovePluggableScreens
}
}
The code is working fine as expected, but if I change the code this way-- without get() for removingPluggableScreens field it does not work as expected,
private val _removingPluggableScreens = mutableStateOf(false)
val removingPluggableScreens: Boolean = _removingPluggableScreens.value
fun updateRemovingPluggableScreens(shouldRemovePluggableScreens: Boolean) {
if (shouldRemovePluggableScreens != _removingPluggableScreens.value) {
_removingPluggableScreens.value = shouldRemovePluggableScreens
}
}
When I observe the state like this, it's not working correctly if I choose the second approach, but it works fine if I choose the first approach:
val removingPluggableScreens = viewModel.removingPluggableScreens
if (removingPluggableScreens) {
// do sth here
}
Simply, I want to know the differences between val removingPluggableScreens: Boolean get() = _removingPluggableScreens.value and val removingPluggableScreens: Boolean = _removingPluggableScreens.value
Thanks in advance.
答案1
得分: 1
当您给变量赋值时，这仅发生一次，在您的情况下是在声明时。将来，您的代码中的这两个变量不以任何方式相关。
当您指定一个getter时，每次读取removingPluggableScreens的值时都会调用它。在您的情况下，这个值将始终与_removingPluggableScreens.value匹配。
英文:
When you assign a value to a variable, this happens only once, in your case, when you declare it. And in the future, these 2 variables in your code are not related in any way.
When you specify a getter, When you specify a getter, it is called every time the value of the removingPluggableScreens is read. And in your case this value will always match the _removingPluggableScreens.value.
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