observer-pattern – Page 3

MediatorLiveData or switchMap transformation with multiple parameters

May 1, 2023 by Tarik

Source : https://plus.google.com/+MichielPijnackerHordijk/posts/QGXF9gRomVi To have multiple triggers for switchMap(), you need to use a custom MediatorLiveData to observe the combination of the LiveData objects – class CustomLiveData extends MediatorLiveData<Pair<String, Integer>> { public CustomLiveData(LiveData<String> code, LiveData<Integer> nbDays) { addSource(code, new Observer<String>() { public void onChanged(@Nullable String first) { setValue(Pair.create(first, nbDays.getValue())); } }); addSource(nbDays, new Observer<Integer>() { … Read more

Python Observer Pattern: Examples, Tips? [closed]

April 18, 2023 by Tarik

However it does lack flexibility. Well… actually, this looks like a good design to me if an asynchronous API is what you want. It usually is. Maybe all you need is to switch from stderr to Python’s logging module, which has a sort of publish/subscribe model of its own, what with Logger.addHandler() and so on. … Read more

How to combine two live data one after the other?

April 14, 2023 by Tarik

You can use my helper method: val profile = MutableLiveData<ProfileData>() val user = MutableLiveData<CurrentUser>() val title = profile.combineWith(user) { profile, user -> “${profile.job} ${user.name}” } fun <T, K, R> LiveData<T>.combineWith( liveData: LiveData<K>, block: (T?, K?) -> R ): LiveData<R> { val result = MediatorLiveData<R>() result.addSource(this) { result.value = block(this.value, liveData.value) } result.addSource(liveData) { result.value = … Read more

Text change notification for an NSTextField

April 11, 2023 by Tarik

If you just want to detect when the value of a text field has changed, you can use the controlTextDidChange: delegate method that NSTextField inherits from NSControl. Just connect the delegate outlet of the NSTextField in the nib file to your controller class, and implement something like this: – (void)controlTextDidChange:(NSNotification *)notification { NSTextField *textField = … Read more

How does AngularJS know when variables change? How does AngularJS dirty checking work?

March 30, 2023 by Tarik

From this link: Angular defines a concept of a so called digest cycle. This cycle can be considered as a loop, during which Angular checks if there are any changes to all the variables watched by all the $scopes. So if you have $scope.myVar defined in your controller and this variable was marked for being … Read more

Rails 3: How to identify after_commit action in observers? (create/update/destroy)

March 5, 2023 by Tarik

I think transaction_include_action? is what you are after. It gives a reliable indication of the specific transaction in process (verified in 3.0.8). Formally, it determines if a transaction included an action for :create, :update, or :destroy. Used in filtering callbacks. class Item < ActiveRecord::Base after_commit lambda { Rails.logger.info “transaction_include_action?(:create): #{transaction_include_action?(:create)}” Rails.logger.info “transaction_include_action?(:destroy): #{transaction_include_action?(:destroy)}” Rails.logger.info “transaction_include_action?(:update): … Read more

C#: events or an observer interface? Pros/cons?

February 19, 2023 by Tarik

Consider an event to be a callback interface where the interface has only one method. Only hook events you need With events, you only need to implement handlers for events you’re interested in handling. In the observer interface pattern, you’d have to implement all methods in the entire interface including implementing method bodies for notification … Read more

Pros and Cons of Listeners as WeakReferences

February 17, 2023 by Tarik

First of all, using WeakReference in listeners lists will give your object different semantic, then using hard references. In hard-reference case addListener(…) means “notify supplied object about specific event(s) until I stop it explicitly with removeListener(..)”, in weak-reference case it means “notify supplied object about specific event(s) until this object will not be used by … Read more

What is difference between observer pattern and reactive programming?

February 16, 2023 by Tarik

Reactive programming is the general paradigm behind easily propagating changes in a data stream through the execution of a program. It’s not a specific pattern or entity per-se, it’s an idea, or style of programming (such as object oriented progamming, functional programming, etc.) Loosely speaking, it’s the concept that when x changes or updates in … Read more

Difference between Observer Pattern and Event-Driven Approach

February 3, 2023 by Tarik

The Observer Pattern is a very special instance. Event-Driven can mean anything. In most Observer Pattern implementations the Observer is an object watching the observee. When the observee is changed, a method of the observer is called. Strictly speaking this is not an “Event”. That means: various different actions on the observee, usually lead to … Read more