I am trying to follow the official Android guide for ViewModels in Kotlin. I literally copy pasted the easiest official example but the syntax seems to be illegal.
This section causes the problem:
private val users: MutableLiveData<List<User>> by lazy {
MutableLiveData().also {
loadUsers()
}
}
The preview gives me this error:
Property delegate must have a 'getValue(DashViewModel, KProperty*>)' method. None of the following functions is suitable.
And if I want to launch the App I get this error:
Type inference failed: Not enough information to infer parameter T in constructor MutableLiveData<T : Any!>()
Please specify it explicitly.
I dont understand those two errors and other questions with the same error seem to have been caused by something different. My guess is that the MutableLiveData().also causes the problem but I do not know why. This is quite odd considering that this is an official example.
It does not appear that you declared a User class.
The second problem is yet another documentation bug, and you need to provide the type in the MutableLiveData constructor call.
So, this works:
package com.commonsware.myapplication
import androidx.lifecycle.LiveData
import androidx.lifecycle.MutableLiveData
import androidx.lifecycle.ViewModel
class User
class MainViewModel : ViewModel() {
private val users: MutableLiveData<List<User>> by lazy {
MutableLiveData<List<User>>().also {
loadUsers()
}
}
fun getUsers(): LiveData<List<User>> {
return users
}
private fun loadUsers() {
// Do an asynchronous operation to fetch users.
}
}
This is quite odd considering that this is an official example.
In general, consider them an illustration of a technique, not necessarily something that you would copy and paste into a project.