DataStore abstraction

Example/Example/Models/HasId.cs

@@ -0,0 +1,8 @@
+using System;
+namespace Example.Models
+{
+    public interface HasId
+    {
+        string Id { get; set; }
+    }
+}

Example/Example/Models/NavItem.cs

@@ -2,9 +2,9 @@
 
 namespace Example.Models
 {
-    public class Item
+    public class NavItem:HasId
     {
-        public string Id { get; set; }
+		public string Id { get; set; }
         public string Text { get; set; }
         public string Description { get; set; }
     }

Example/Example/Services/BaseDataStore.cs

@@ -0,0 +1,50 @@
+using System;
+using System.Collections.Generic;
+using System.Collections.ObjectModel;
+using System.Linq;
+using System.Threading.Tasks;
+
+namespace Example.Services
+{
+    public partial class BaseDataStore<T> : IDataStore<T> where T : Models.HasId
+    {
+        protected List<T> items;
+
+        public BaseDataStore()
+        {
+        }
+
+        public async Task<bool> AddItemAsync(T item)
+        {
+            items.Add(item);
+            return await Task.FromResult(true);
+        }
+
+        public async Task<bool> DeleteItemAsync(T item)
+        {
+            var _item = items.AsQueryable().Where((T arg) => arg.Id == item.Id).FirstOrDefault();
+            items.Remove(_item);
+
+            return await Task.FromResult(true);
+        }
+
+        public async Task<T> GetItemAsync(string id)
+        {
+            return await Task.FromResult(items.FirstOrDefault(s => s.Id == id));
+        }
+
+        public async Task<IEnumerable<T>> GetItemsAsync(bool forceRefresh = false)
+        {
+            return await Task.FromResult(items);
+        }
+
+        public async Task<bool> UpdateItemAsync(T item)
+        {
+            var _item = items.Where<T>((T arg) => arg.Id == item.Id).FirstOrDefault();
+            items.Remove(_item);
+            items.Add(item);
+
+            return await Task.FromResult(true);
+        }
+    }
+}

Example/Example/Services/NavigationDataStore.cs

@@ -0,0 +1,30 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Threading.Tasks;
+
+using Example.Models;
+
+[assembly: Xamarin.Forms.Dependency(typeof(Example.Services.NavigationDataStore))]
+namespace Example.Services
+{
+    public class NavigationDataStore : BaseDataStore<NavItem>
+    {
+
+        public NavigationDataStore()
+        {
+            items = new List<NavItem>();
+            var mockItems = new List<NavItem>
+            {
+                new NavItem { Id = Guid.NewGuid().ToString(), Text = "First item", Description="This is an item description." },
+                new NavItem { Id = Guid.NewGuid().ToString(), Text = "Second item", Description="This is an item description." },
+                new NavItem { Id = Guid.NewGuid().ToString(), Text = "Third item", Description="This is an item description." },
+                new NavItem { Id = Guid.NewGuid().ToString(), Text = "Fourth item", Description="This is an item description." },
+                new NavItem { Id = Guid.NewGuid().ToString(), Text = "Fifth item", Description="This is an item description." },
+                new NavItem { Id = Guid.NewGuid().ToString(), Text = "Sixth item", Description="This is an item description." },
+            };
+
+            mockItems.ForEach(item => items.Add(item));
+        }
+    }
+}

Example/Example/ViewModels/AboutViewModel.cs

@@ -5,7 +5,7 @@
 
 namespace Example.ViewModels
 {
-    public class AboutViewModel : BaseViewModel
+    public class AboutViewModel : BaseViewModel<Object>
     {
         public AboutViewModel()
         {

Example/Example/ViewModels/BaseViewModel.cs

@@ -10,9 +10,9 @@
 
 namespace Example.ViewModels
 {
-    public class BaseViewModel : INotifyPropertyChanged
+    public class BaseViewModel<It> : INotifyPropertyChanged
     {
-        public IDataStore<Item> DataStore => DependencyService.Get<IDataStore<Item>>() ?? new MockDataStore();
+        public IDataStore<It> DataStore => DependencyService.Get<IDataStore<It>>();
 
         bool isBusy = false;
         public bool IsBusy

Example/Example/ViewModels/NavItemDetailVM.cs

@@ -4,10 +4,10 @@
 
 namespace Example.ViewModels
 {
-    public class ItemDetailViewModel : BaseViewModel
+    public class NavItemDetailVM : BaseViewModel<NavItem>
     {
-        public Item Item { get; set; }
-        public ItemDetailViewModel(Item item = null)
+        public NavItem Item { get; set; }
+        public NavItemDetailVM(NavItem item = null)
         {
             Title = item?.Text;
             Item = item;

Example/Example/ViewModels/NavItemVM.cs

@@ -10,20 +10,20 @@
 
 namespace Example.ViewModels
 {
-    public class ItemsViewModel : BaseViewModel
+    public class NavItemVM : BaseViewModel<NavItem>
     {
-        public ObservableCollection<Item> Items { get; set; }
+        public ObservableCollection<NavItem> Items { get; set; }
         public Command LoadItemsCommand { get; set; }
 
-        public ItemsViewModel()
+        public NavItemVM()
         {
             Title = "Browse";
-            Items = new ObservableCollection<Item>();
+            Items = new ObservableCollection<NavItem>();
             LoadItemsCommand = new Command(async () => await ExecuteLoadItemsCommand());
 
-            MessagingCenter.Subscribe<NewItemPage, Item>(this, "AddItem", async (obj, item) =>
+            MessagingCenter.Subscribe<NewItemPage, NavItem>(this, "AddItem", async (obj, item) =>
             {
-                var _item = item as Item;
+                var _item = item as NavItem;
                 Items.Add(_item);
                 await DataStore.AddItemAsync(_item);
             });

Example/Example/Views/ItemDetailPage.xaml.cs

@@ -11,9 +11,9 @@ namespace Example.Views
 	[XamlCompilation(XamlCompilationOptions.Compile)]
 	public partial class ItemDetailPage : ContentPage
 	{
-        ItemDetailViewModel viewModel;
+        NavItemDetailVM viewModel;
 
-        public ItemDetailPage(ItemDetailViewModel viewModel)
+        public ItemDetailPage(NavItemDetailVM viewModel)
         {
             InitializeComponent();
 
@@ -24,13 +24,13 @@ public ItemDetailPage()
         {
             InitializeComponent();
 
-            var item = new Item
+            var item = new NavItem
             {
                 Text = "Item 1",
                 Description = "This is an item description."
             };
 
-            viewModel = new ItemDetailViewModel(item);
+            viewModel = new NavItemDetailVM(item);
             BindingContext = viewModel;
         }
     }

Example/Example/Views/ItemsPage.xaml.cs

@@ -16,22 +16,22 @@ namespace Example.Views
 	[XamlCompilation(XamlCompilationOptions.Compile)]
 	public partial class ItemsPage : ContentPage
 	{
-        ItemsViewModel viewModel;
+        NavItemVM viewModel;
 
         public ItemsPage()
         {
             InitializeComponent();
 
-            BindingContext = viewModel = new ItemsViewModel();
+            BindingContext = viewModel = new NavItemVM();
         }
 
         async void OnItemSelected(object sender, SelectedItemChangedEventArgs args)
         {
-            var item = args.SelectedItem as Item;
+            var item = args.SelectedItem as NavItem;
             if (item == null)
                 return;
 
-            await Navigation.PushAsync(new ItemDetailPage(new ItemDetailViewModel(item)));
+            await Navigation.PushAsync(new ItemDetailPage(new NavItemDetailVM(item)));
 
             // Manually deselect item.
             ItemsListView.SelectedItem = null;

Example/Example/Views/NewItemPage.xaml.cs

@@ -11,13 +11,13 @@ namespace Example.Views
     [XamlCompilation(XamlCompilationOptions.Compile)]
     public partial class NewItemPage : ContentPage
     {
-        public Item Item { get; set; }
+        public NavItem Item { get; set; }
 
         public NewItemPage()
         {
             InitializeComponent();
 
-            Item = new Item
+            Item = new NavItem
             {
                 Text = "Item name",
                 Description = "This is an item description."