在 kotlin coroutines 实验室示例中, https: //codelabs.developers.google.com/codelabs/kotlin-coroutines/#6
它通过传递MainViewModel.FACTORY(repository)
val viewModel = ViewModelProviders
.of(this, MainViewModel.FACTORY(repository))
.get(MainViewModel::class.java)
MainViewModel 如下,不明白里面::MainViewModel
用了什么语法
val FACTORY = singleArgViewModelFactory(::MainViewModel)
singleArgViewModelFactory
has 构造函数:
singleArgViewModelFactory(constructor: (A) -> T)
哪个取一个函数(A) -> T
,里面的那个是什么::MainViewModel
意思 singleArgViewModelFactory(::MainViewModel)
?
class MainViewModel(private val repository: TitleRepository) : ViewModel() {
companion object {
/**
* Factory for creating [MainViewModel]
*
* @param arg the repository to pass to [MainViewModel]
*/
val FACTORY = singleArgViewModelFactory(::MainViewModel)
}
......
}
fun <T : ViewModel, A> singleArgViewModelFactory(constructor: (A) -> T):
(A) -> ViewModelProvider.NewInstanceFactory {
return { arg: A ->
object : ViewModelProvider.NewInstanceFactory() {
@Suppress("UNCHECKED_CAST")
override fun <V : ViewModel> create(modelClass: Class<V>): V {
return constructor(arg) as V
}
}
}
}