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kotlinlang

Screenshot 2019-04-12 10.23.57.png

I was trying out the Factory pattern. What do you guys recommend? Using a constructor or factory pattern? (I know the use of isXavailable and isXabsent is not smart, but copied something from iOS sourceCode, still need to fix this)

Constructor, I don’t see why you need this create method, it’s perfectly work to pass model in primary constructor

Not in primary, that one needs to be an empty constructor. I use it in the 2nd constructor

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Depending on why you needed an empty constructor, this may not work. Actually, I’m not sure.

If you have some reflection looking for a constructor without arguments, would it find something if you only have a constructor with default values for all parameters?

Thanks for mentioning, I tried val viewModel = MedicationAgreementRequesterViewModel::class.java.newInstance() and this just works :wink:

Screenshot 2019-04-12 10.56.55.png

ViewModelView : ```abstract class ViewModelView : ViewModel(), LayoutResIdProvider```

LayoutReIdProvider: ```interface LayoutResIdProvider {
    var layoutResId: Int
}
```

Used in a RecyclerView in combination with DataBinding :wink:

Damn, I still need a init, because I have this updateForChanged()  method which accesses the properties. Guess it’s time to learn about delegates, I understand them, but don’t know when or how to use them exactly

<@UHR6D441L> this seems weird. ViewModelView, has a layoutResProvider, which seems like a anti pattern. The layout shouldn't be coupled to a ViewModel at all...Even with databinding. For one or more constructors, you will need to create a inner class that inherits from ViewModelProvider.Factory and override the create(modelClass: Class&lt;T&gt;). if not Viewmodel won't work as intended.

Well I use the ViewModel inside a recyclerview and and use the layoutResId as viewType to create a viewholder. So it saves me a lot of work

Yea its a anti pattern.  instead ,specify the layout res in your recyclerview

It may work but its a bad practice, and also leads to things not being flexible

Hmm, I thought it was just flexible :sweat_smile:

Screenshot 2019-04-12 16.44.13.png

Are you sure? I really liked this simple Adapter…

Nah, not at all. .. if you put specify the layout res in the viewmodel, that means the viewmodel should only work with that layout.

I dont see that as a problem. I just want to bind a specific viewmodel to a specific view

lol whats the point of putting list[position].layoutResId ,if its always going to be the same Layout Re

No, I can add a generic list into this adapter

Each viewmodel has its own layout, and I made a factory pattern to bind a object to a layout.

Oh ok... But at this point ,your factory method isn't using the Viewmodel provider.factory, so is Extending from Viewmodel even useful at this point?

why not just extend from LayoutResIdProvider directly

Just out of curiosity, doesn’t this pattern break if you want multiple types in a list?

<@U4MLMD6UA> judging by the actual implementation, each type would need its on ViewModelView.