Why isnt observable working when I am trying with single observable

Question

I am a bit confused about observable single object and list of objects

when i do the following with Observable> then it works

retrofit interface MainApi:

    Observable<Todo> getTodos();

in activity:

    mainApi.getTodos()
    .subscribeOn(Schedulers.io())
            .concatMap(new Function<List<Todo>, ObservableSource<Todo>>() {
                @Override
                public ObservableSource<Todo> apply(List<Todo> todos) throws Exception {
                      return Observable.fromIterable(todos).subscribeOn(Schedulers.io());
                }
            })
            .subscribe(new Observer<Todo>() {
                @Override
                public void onSubscribe(Disposable d) {
                    Log.d("LogMe", ">>>Inside susbcribed>>>");
                }

                @Override
                public void onNext(Todo todo) {
                    Log.d("LogMe", ">>>Inside onNExt>>>" +  todo.getName());

                }

                @Override
                public void onError(Throwable e) {
                    Log.d("LogMe", ">>>Inside onError>>>" +e.toString());
                }

                @Override
                public void onComplete() {
                    Log.d("LogMe", ">>>Inside onComplete>>>");
                }
            });

But when use Observable then it doesnt work.

retrofit interface MainApi:

    Observable<Todo> getTodos();

in activity:

    mainApi.getTodos().subscribeOn(Schedulers.io())
        .map(new Function<Todo, String>() {

            @Override
            public  String apply(Todo todo) throws Exception {
            return todo.getName();
            }
        })
        .doOnNext(new Consumer<String>() {
            @Override
            public void accept(String stringObservable) throws Exception {
            Log.d("LogMe", ">>>Inside >>> doOnNext");
            }
        })
    .subscribe(new Observer<String>() {
               @Override
               public void onSubscribe(Disposable d) {
               Log.d("LogMe", ">>>Inside susbcribed>>>");
               }

               @Override
               public void onNext(String stringObservable) {
               Log.d("LogMe", ">>>Inside onNExt>>>");
               }

               @Override
               public void onError(Throwable e) {
               Log.d("LogMe", ">>>Inside onError>>>" +e.toString());
               }

               @Override
               public void onComplete() {
               Log.d("LogMe", ">>>Inside Presenter onComplete>>>");
               }
           });

then i get the error:

LogMe: >>>Inside Presenter onError>>>com.google.gson.JsonSyntaxException: java.lang.IllegalStateException: Expected BEGIN_OBJECT but was BEGIN_ARRAY at line 1 column 2 path $

Where am I going wrong? If its possible to get the result with single observable then how do i iterate through each item/object of Todo?

Answer 1

com.google.gson.JsonSyntaxException: java.lang.IllegalStateException: Expected BEGIN_OBJECT but was BEGIN_ARRAY at line 1 column 2 path

The error is from the Gson library.

Why this Error, What this error means?

This error simply means Gson can't deserialize JSON to Java Object. because Gson is expecting a JSON object and unexpectedly it received a JSON Array from the response.

How to Fix it?

You can fix it easily by changing the return type of Observable<Todo> getTodos(); to Observable<List<Todo>> getTodos();

Hope this helps!!

Happy Coding :)