Editor

UserViewModel.java

/*
 * Copyright (C) 2017 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.example.android.observability.ui;

import android.arch.lifecycle.ViewModel;

import com.example.android.observability.UserDataSource;
import com.example.android.observability.persistence.User;

import io.reactivex.Completable;
import io.reactivex.Flowable;
import io.reactivex.functions.Action;
import io.reactivex.functions.Function;
import io.reactivex.internal.operators.completable.CompletableFromAction;

/**
 * View Model for the {@link UserActivity}
 */
public class UserViewModel extends ViewModel {

private final UserDataSource mDataSource;

private User mUser;

public UserViewModel(UserDataSource dataSource) {
        mDataSource = dataSource;
    }

/**
     * Get the user name of the user.
     *
     * @return a {@link Flowable} that will emit every time the user name has been updated.
     */
    public Flowable<String> getUserName() {
        return mDataSource.getUser()
                // for every emission of the user, get the user name
                .map(user -> {
                    mUser = user;
                    return user.getUserName();
                });

}

/**
     * Update the user name.
     *
     * @param userName the new user name
     * @return a {@link Completable} that completes when the user name is updated
     */
    public Completable updateUserName(final String userName) {
        return new CompletableFromAction(() -> {
            // if there's no use, create a new user.
            // if we already have a user, then, since the user object is immutable,
            // create a new user, with the id of the previous user and the updated user name.
            mUser = mUser == null
                    ? new User(userName)
                    : new User(mUser.getId(), userName);

mDataSource.insertOrUpdateUser(mUser);
        });
    }
}