CODEWITHSUNDEEP
androidmvvmandroid-livedataandroid-viewmodel
user9591909
user9591909

Reputation:

How to communicate between a Repository and ViewModel class when Retrofit either fails or success with an requests?

For many years I have been developing Android apps with the MVP pattern but I'm now trying to learn MVVM with ViewModel and LiveData

In the following example I'm not getting how I would communicate a failure or successful result upon a POST or GET request with Retrofit

Before with MVP I would with use a Listener to communicate presenter with either listener.onTodoFetched() or listener.onTodoFetchError() and then reacting differently based on which method gets called. Should I still communicate in this way with my ViewModel class?

FetchTodoRepository.java

public MutableLiveData<String> fetchTodo() {
    retrofitService.getRetrofitService().create(Endpoints.class).getTodo().enqueue(new Callback<String>() {
        @Override
        public void onResponse(Call<String> call, Response<String> response) {

            if (response.isSuccessful() && response.body() != null) {
                listener.onTodoFetched(response.body());     //ViewModel equivalent?
            } else {
                listener.onTodoFetchError(response.message());     //ViewModel equivalent?
            }

        }

        @Override
        public void onFailure(Call<String> call, Throwable t) {
            listener.onTodoFetchError(t.getMessage());     //ViewModel equivalent?
        }
    });

    return mutableLiveData;
}

UPDATE:

Based on answers and further research one could use the following methods:

Upvotes: 9

Views: 5047

Answers (3)

rahul g
rahul g

Reputation: 5

It's easy to implement.

Just use HTTP status code. In response you'll get status code, just send it to viewmodel and in viewmodel you can easily send it to Activity or fragment by observing it.

Eg. 200 - Ok 400 - Bad request etc.

I don't know it helps you or not but this thing works for me.

Upvotes: 0

Mitesh Vanaliya
Mitesh Vanaliya

Reputation: 2611

Communication between Repository and ViewModel using Higher-Oder Functions Pass function as Argument into repository method

For Example in Repository method like this: 

fun repoMethod(id : Int, viewModelCallBack : (List<CustomeDto>) -> Unit)
{
     //Your API call
     .....
    viewModelCallBack(response.body())

}

And View Model Method like 

    fun viewModelMethod()
    {
       repoObj.repoMethod(5){ listOfValueReturnFromApi ->
            //Here listOfValueReturnFromApi is API response using Higher Order function in kotlin
        }

    }

Upvotes: 4

haresh
haresh

Reputation: 1420

When you are using mvvm with livedata you really don't need to use interface to pass the data to viewmodel.

MutableLiveData has method setValue() pass your response in that and then when you will call this fetchTodo() method in viewmodel you will get all your data.

Try below code

  public MutableLiveData<String> fetchTodo() {
retrofitService.getRetrofitService().create(Endpoints.class).getTodo().enqueue(new 
Callback<String>() {
    @Override
    public void onResponse(Call<String> call, Response<String> response) {

        if (response.isSuccessful() && response.body() != null) {
            mutableLiveData.setValue(response.body())
        } else {
             mutableLiveData.setValue(response.message());    
        }

    }

    @Override
    public void onFailure(Call<String> call, Throwable t) {
         mutableLiveData.setValue(t.message());    //ViewModel equivalent?
    }
});

return mutableLiveData;
}

In your viewmodel :

 public LiveData<String> fetchTodo()
{
 return yourRepoInstance.fetchTodo() ; here you will get result data
}

Upvotes: 2

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