observer-pattern

Typically, in Java, when I've got an object who's providing some sort of notification to other objects, I'll employ the Listener/Observer pattern. Is there a more Scala-like way to do this? Should I be using this pattern in Scala, or is there something else baked into the language I should be taking advantage of? Alex Cruise You can still accumulate a list of callbacks, but you can just make them functions instead of having to come up with yet another single method interface. e.g. case class MyEvent(...) object Foo { var listeners: List[MyEvent => ()] = Nil def listen(listener: MyEvent => ())

I am using Reactive extensions for NET (Rx) with Caliburn.Micro in my WPF app. I'm trying to port my WPF app to use an MVVM architecture and I need to monitor changes in the Text property of a TextBox control. If the last change of the Text property was more than 3 seconds ago I need to call the LoadUser method of a service. Porting the logic from my old solution to the new solution with MVVM architecture. OLD XAML: <TextBox Name="Nick" Grid.Row="0" FontSize="14" Margin="2,2,2,2" HorizontalAlignment="Stretch" TextChanged="Nick_TextChanged" /> In code behind I have this: ... Observable

Suppose you have an ActiveRecord::Observer in one of your Ruby on Rails applications - how do you test this observer with rSpec? Pete You are on the right track, but I have run into a number of frustrating unexpected message errors when using rSpec, observers, and mock objects. When I am spec testing my model, I don't want to have to handle observer behavior in my message expectations. In your example, there isn't a really good way to spec "set_status" on the model without knowledge of what the observer is going to do to it. Therefore, I like to use the "No Peeping Toms" plugin. Given your

I've got the following (simplified): interface IFindFilesObserver { void OnFoundFile(FileInfo fileInfo); void OnFoundDirectory(DirectoryInfo directoryInfo); } class FindFiles { IFindFilesObserver _observer; // ... } ...and I'm conflicted. This is basically what I would have written in C++, but C# has events. Should I change the code to use events, or should I leave it alone? What are the advantages or disadvantages of events over a traditional observer interface? Consider an event to be a callback interface where the interface has only one method. Only hook events you need With events you only

How do we ususaly deal with a vector whose elements are pointers to object? My specific question is the comment at the end of the code supplied below. Thanks. class A { public: virtual int play() = 0 ; }; class B : public A { public: int play() {cout << "play in B " << endl;}; }; class C : public A { public: int play() {cout << "play in C " << endl;}; }; int main() { vector<A *> l; l.push_back(new B()); l.push_back(new C()); for(int i = 0 ; i < l.size();i++) { l[i]->play(); } //Do i have to do this to avoid memory leak? It is akward. Any better way to do this? for(int i = 0 ; i < l.size();i++)

I'm trying to fire an event when an integer value is updated, but it's failing. Here's the code I'm using: Declaring The Custom Listener public class fieldactivity extends AppCompatActivity implements View.OnClickListener { OnModeUpdate modeupdate; //Create custom listener for mode update int mode = 1; Mode Update Code protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.fieldsignals); Button button = (Button) findViewById(R.id.mode_rotate_button); button.setOnClickListener(this); } @Override public void onClick(View v) { switch (v