I have the following property and pseudo-code method:
private DataModelMember _PropertyMember = new DataModelMember();
public DataModelMember PropertyMember
{
get { return _PropertyMember; }
}
void GetWCFData()
{
DataModel d = client.getWCFData();
this._PropertyMember = d.result.anotherclass; //*(DataModelMember is anotherclass)
}
So, "this._PropertyMember = value" does in fact change the private member, it however does not update any of the properties inside (as evident with the databinding). It almost seems like my 'DataModelMember' class needs to inherit some other interface to notify of the class copy?
INotifyPropertyChanged is not magic.
You need to raise the PropertyChanged event yourself whenever the property changes.
Related
A custom object that takes a parameter of (DocumentSnapShot documentsnapShot). also is an inner object from Firebase that retrieves a snapshot and set the values to my custom model also have its argument (DocumentSnapShot documentsnapShot). However, I wish to get the data from Firebase and pass it to my custom argument because mine takes multiple data not only Firebase. And it's not possible to iterate Firestore without an override.
Here's the code:
public UserSettings getUserSettings(DocumentSnapshot documentSnapshot){
Log.d(TAG, "getUserSettings: retrieving user account settings from firestore");
DocumentReference mSettings = mFirebaseFirestore.collection("user_account_settings").document(userID);
mSettings.get().addOnSuccessListener(new OnSuccessListener<DocumentSnapshot>() {
#Override
public void onSuccess(DocumentSnapshot documentSnapshot) {
UserAccountSettings settings = documentSnapshot.toObject(UserAccountSettings.class);
settings.setDisplay_name(documentSnapshot.getString("display_name"));
settings.setUsername(documentSnapshot.getString("username"));
settings.setWebsite(documentSnapshot.getString("website"));
settings.setProfile_photo(documentSnapshot.getString("profile_photo"));
settings.setPosts(documentSnapshot.getLong("posts"));
settings.setFollowers(documentSnapshot.getLong("followers"));
settings.setFollowing(documentSnapshot.getLong("following"));
}
});
}
You cannot return something now that hasn't been loaded yet. Firestore loads data asynchronously, since it may take some time for this. Depending on your connection speed and the state, it may take from a few hundred milliseconds to a few seconds before that data is available. If you want to pass settings object to another method, just call that method inside onSuccess() method and pass that object as an argument. So a quick fix would be this:
#Override
public void onSuccess(DocumentSnapshot documentSnapshot) {
UserAccountSettings settings = documentSnapshot.toObject(UserAccountSettings.class);
yourMethod(settings);
}
One more thing to mention is that you don't need to set the those values to object that already have them. You are already getting the data from the database as an object.
So remember, onSuccess() method has an asynchronous behaviour, which means that is called even before you are getting the data from your database. If you want to use the settings object outside that method, you need to create your own callback. To achieve this, first you need to create an interface like this:
public interface MyCallback {
void onCallback(UserAccountSettings settings);
}
Then you need to create a method that is actually getting the data from the database. This method should look like this:
public void readData(MyCallback myCallback) {
DocumentReference mSettings = mFirebaseFirestore.collection("user_account_settings").document(userID);
mSettings.get().addOnSuccessListener(new OnSuccessListener<DocumentSnapshot>() {
#Override
public void onSuccess(DocumentSnapshot documentSnapshot) {
UserAccountSettings settings = documentSnapshot.toObject(UserAccountSettings.class);
myCallback.onCallback(settings);
}
});
}
In the end just simply call readData() method and pass an instance of the MyCallback interface as an argument wherever you need it like this:
readData(new MyCallback() {
#Override
public void onCallback(UserAccountSettings settings) {
Log.d("TAG", settings.getDisplay_name());
}
});
This is the only way in which you can use that object of UserAccountSettings class outside onSuccess() method. For more informations, you can take also a look at this video.
Use LiveData as return type and observe the changes of it's value to execute desired operation.
private MutableLiveData<UserAccountSettings> userSettingsMutableLiveData = new MutableLiveData<>();
public MutableLiveData<UserAccountSettings> getUserSettings(DocumentSnapshot documentSnapshot){
DocumentReference mSettings = mFirebaseFirestore.collection("user_account_settings").document(userID);
mSettings.get().addOnSuccessListener(new OnSuccessListener<DocumentSnapshot>() {
#Override
public void onSuccess(DocumentSnapshot documentSnapshot) {
UserAccountSettings settings = documentSnapshot.toObject(UserAccountSettings.class);
settings.setDisplay_name(documentSnapshot.getString("display_name"));
settings.setUsername(documentSnapshot.getString("username"));
settings.setWebsite(documentSnapshot.getString("website"));
settings.setProfile_photo(documentSnapshot.getString("profile_photo"));
settings.setPosts(documentSnapshot.getLong("posts"));
settings.setFollowers(documentSnapshot.getLong("followers"));
settings.setFollowing(documentSnapshot.getLong("following"));
userSettingsMutableLiveData.setValue(settings);
}
});
return userSettingsMutableLiveData;
}
Then from your Activity/Fragment observe the LiveData and inside onChanged do your desired operation.
getUserSettings().observe(this, new Observer<UserAccountSettings>() {
#Override
public void onChanged(UserAccountSettings userAccountSettings) {
//here, do whatever you want on `userAccountSettings`
}
});
So i have a class that makes an array list for me and i need to access it in another class through a constructor but i don't know what to put into the constructor because all my methods in that class are just for manipulating that list. im either getting a null pointer exception or a out of bounds exception. ive tried just leaving the constructor empty but that dosent seem to help. thanks in advance. i would show you code but my professor is very strict on academic dishonesty so i cant sorry if that makes it hard.
You are confusing the main question, with a potential solution.
Main Question:
I have a class ArrayListOwnerClass with an enclosed arraylist property or field.
How should another class ArrayListFriendClass access that property.
Potential Solution:
Should I pass the arraylist from ArrayListOwnerClass to ArrayListFriendClass,
in the ArrayListFriendClass constructor ?
It depends on what the second class does with the arraylist.
Instead of passing the list thru the constructor, you may add functions to read or change, as public, the elements of the hidden internal arraylist.
Note: You did not specify a programming language. I'll use C#, altought Java, C++, or similar O.O.P. could be used, instead.
public class ArrayListOwnerClass
{
protected int F_Length;
protected ArrayList F_List;
public ArrayListOwnerClass(int ALength)
{
this.F_Length = ALength;
this.F_List = new ArrayList(ALength);
// ...
} // ArrayListOwnerClass(...)
public int Length()
{
return this.F_Length;
} // int Length(...)
public object getAt(int AIndex)
{
return this.F_List[AIndex];
} // object getAt(...)
public void setAt(int AIndex, object AValue)
{
this.F_List[AIndex] = AValue;
} // void setAt(...)
public void DoOtherStuff()
{
// ...
} // void DoOtherStuff(...)
// ...
} // class ArrayListOwnerClass
public class ArrayListFriendClass
{
public void UseArrayList(ArrayListOwnerClass AListOwner)
{
bool CanContinue =
(AListOwner != null) && (AListOwner.Length() > 0);
if (CanContinue)
{
int AItem = AListOwner.getAt(5);
DoSomethingWith(Item);
} // if (CanContinue)
} // void UseArrayList(...)
public void AlsoDoesOtherStuff()
{
// ...
} // void AlsoDoesOtherStuff(...)
// ...
} // class ArrayListFriendClass
Note, that I could use an indexed property.
I've tried following the steps in Joost Van Schaik's article on tombstoning but was unable to get it to work for me. I'm no doubt doing something wrong. In my ViewModel:
private string _foobar ="init";
public string testStr
{
get
{
return _foobar;
}
set
{
_foobar = value;
}
}
And in my page:
<TextBox x:Name="tBoxTest" Text="{Binding testStr, Mode=TwoWay}" />
While the application is running, changing the value in tBoxTest sets _foobar just fine, but try to serialize it and it’s as if it has forgotten the instance??? Any help would be greatly appreciated.
I was able to get tombstoning to work, along with having an object be visible to all my ViewModels, by doing the following:
In a Model class, I added:
private static Model1 _instance;
public static Model1 Instance
{
get { return _instance; }
set { _instance = value; }
}
public static void CreateNew()
{
if (_instance == null)
{
_instance = new Model1();
_instance.FirstString = "init";
}
}
Then in ApplicationExtensions.cs I added:
public static void SaveToIsolatedStorage(this Application app, Model1 model)
{
var dataFileName = GetIsFile((model.GetType()));
using (var userAppStore =
IsolatedStorageFile.GetUserStoreForApplication())
{
if (userAppStore.FileExists(dataFileName))
{
userAppStore.DeleteFile(dataFileName);
}
using (var iss = userAppStore.CreateFile(dataFileName))
{
SilverlightSerializer.Serialize(model, iss);
}
}
}
And in App.xaml.cs I changed LoadModel() to:
private void LoadModel()
{
try
{
Model1.Instance = this.RetrieveFromIsolatedStorage<Model1>();
}
catch (Exception) { }
if (Model1.Instance == null) Model1.CreateNew();
}
That all made things like this work in my ViewModel files:
public string TestStr
{
get
{
return Model1.Instance.FirstString;
}
set
{
Model1.Instance.FirstString = value;
}
}
And by that, I mean that the Model1 object is getting serialized and tombstoning is working - at least I’m getting what I think I want. I’ve tested it a lot by navigating between apps, phone settings, turning the phone off and on, locking it and calling it while in the app from another phone. Performance when deserializing is great. And I can work with the vars.
That said, Mr. Van Schaik replied to a request for assistance with: "If you are subclassing from an MVVMLight ViewModelBase it does, and then you should call RaisePropertyChanged from your setter like this:
private string _foobar ="init";
public string TestStr
{
get
{
return _foobar;
}
set
{
RaisePropertyChanged("TestStr");
_foobar = value;
}
}
RaisePropertyChanged notifies any listenings views (i.e. the TextBox you bound to it) that a property is changed and that the should update their contents. This is a crucial mechanism."
So I will work with what I was originally trying but with the addition of RaisePropertyChanged to see what that does.
UPDATE
Although I implemented RaisedPropertyChanged (using the code snippet mvvminpc) in my MainViewModel.cs file, that still had no effect (as good as it may be for other things) on serializing anything created within the ViewModel. I'm probably still doing something wrong, but it may also be because view models inherit from a protected class (answer from Laurent Bugnion). I (very reluctantly) tried changing that class from protected to public and recompiling, but it didn't help in my case and I hate to fork a referenced library like that. Anyway, I'm just forging ahead for now with creating the Model1 instance in App.xaml.cs. Seems to work. While I was at it, I modified one of Van Schaik's methods to accept any type of object:
public static void SaveToIsolatedStorage<T>(this Application app, T obj)
where T : class
{
var dataFileName = GetIsFile(typeof(T));
using (var userAppStore =
IsolatedStorageFile.GetUserStoreForApplication())
{
if (userAppStore.FileExists(dataFileName))
{
userAppStore.DeleteFile(dataFileName);
}
using (var iss = userAppStore.CreateFile(dataFileName))
{
SilverlightSerializer.Serialize(obj, iss);
}
}
}
From the code you've posted there isn't an instant answer.
My advice to debug this is:
if you've copied the code exactly from that article then add something (a messagebox?) to the empty catch handler - `catch (Exception){ }
use the debugger to put breakpoints in the LoadModel and SaveToIsolatedStorage methods
use these breakpoints to step through the Load and Save code - is the code correctly loading and saving?
To be honest, with problems like this, doing a little investigation yourself is much better than asking questions on here (IMO!)
How does undo work? Does it copy all the managed objects every time any of the values change? Or does it only copy the actual changes together with an information which objects were affected? Is that heavy or lightweight?
The 'undo' mechanism for pretty much any language that supports Object-Oriented constructs uses the Memento Design Pattern to make it happen.
Here's a rough implementation to get you thinking. This handles your stack of undoable operations. (It doesn't handle redo, but that's easy to support by replacing the stack with a list and keeping track of the current item.)
public class Undoable {
public static void Do(Action do, Action undo) {
do();
sUndoStack.Push(new Undoable(do, undo));
}
public static void Undo() {
sUndoStack.Pop().mUndoCallback();
}
private Undoable(Action doCallback, undoCallback) {
mDoCallback = doCallback;
mUndoCallback = undoCallback;
}
private Action mDoCallback, mUndoCallback;
// note: using a global stack here is lame, but works for demo purposes
private static readonly Stack<Undoable> sUndoStack = new Stack<Undoable>();
}
To use this, let's say the user can change a value in some object like this:
public class Foo {
public string Bar {
get { return mBar; }
set {
if (mBar != value) {
mBar = value;
}
}
}
private string mBar;
}
To make that operation undoable, we just change the setter to:
set {
if (mBar != value) {
string oldValue = mBar;
Undoable.Do(() => mBar = value,
() => mBar = oldValue);
}
}
Now, if you call Undoable.Undo() from anywhere in the application, your instance of Foo will restore the previous value of Bar. If Foo also raises an event when Bar changes (not shown here), the UI will also properly refresh on undo too.
I have a method that should only be called when a property of a specific object is set to false. This is its initial value. After the first call, the property is set to true, ensuring that the call is only ever made once.
However, when I mock the class that performs this change, the mock object does not change the property of the underlying object.
Is there a way to force a change of a property on an object is response to an Expectation being met?
Something along the lines of...
Expect.Call(mockedObject.TestMethod(underlyingObject)).NowDoThis(delegate() { underlyingObject.Processed = true; });
Yes,
instead of your NowDoThis() call try Do()
Finally home so I can try out some code.
The trick is to cast the anonymous delegate to type Action that derrives from System.Delegate (type MethodInvoker should also work but that type is only available in System.Windows.Forms)
Here's the code. I'm more comfortable with the rhino mocks AAA syntax. Let me know if I have to convert it to Expect.Call syntax. I'm also using xunit.net, [Fact] just means [Test]
public interface Thingie
{
bool Flag { get; set; }
void DoSomething();
}
[Fact]
public void Test()
{
var thingie = MockRepository.GenerateStub<Thingie>();
thingie.Stub(x => x.DoSomething()).Do((Action) delegate { thingie.Flag = true; });
Assert.False(thingie.Flag);
thingie.DoSomething();
Assert.True(thingie.Flag);
}
Assuming mockedObject is, in fact, a mock object, you can simply set a return value for your property after the test method has been called:
bool isProcessed = false;
Expect.Call(mockedObject.TestMethod(underlyingObject))
.Do(new Action(() => isProcessed = true));
SetupResult.For(mockedObject.Processed).Return(isProcessed);