In the context of a Flutter 2.0.5 app whose state I'd like to manage with Riverpod, I thought I can declare a StateNotifierProvider like this:
import 'package:flutter_riverpod/flutter_riverpod.dart';
final counterProvider = StateNotifierProvider<CounterStateNotifier>((ref) => CounterStateNotifier());
class CounterStateNotifier extends StateNotifier<int> {
CounterStateNotifier([int count = 0]) : super(count);
void increment() => state++;
}
But Android Studio (and later the Dart compiler as well) complains about the line where I declare the counterProvider variable:
The type 'StateNotifierProvider' is declared with 2 type parameters, but 1 type arguments were given.
Removing the <CounterStateNotifier> type parameter in StateNotifierProvider<CounterStateNotifier> removes the error. However, attempting to read the provider and call its increment method (setting () => context.read(counterProvider).increment() as the onPressed of an ElevatedButton, then pressing the button) gives the following runtime error:
'increment'
method not found
Receiver: 0
Arguments: []
Why is context.read(counterProvider) returning the int state instead of the notifier? And what is the reason behind the type parameter error mentioned in the first part of my question?
I should mention that I'm running my app on the web (with flutter run -d Chrome).
As of Riverpod 0.14.0, State is the default value exposed by StateNotifierProvider.
The syntax for declaring your StateNotifierProvider is now as follows:
final counterProvider = StateNotifierProvider<CounterStateNotifier, int>((ref) => CounterStateNotifier());
Accessing functions now requires adding .notifier (accessing the StateNotifier itself):
context.read(counterProvider.notifier).increment();
And like you've noticed, you now access the state like so:
final count = context.read(counterProvider);
More on the changes here.
You may also use dynamic to accept any type if value for the StateNotifierProvider
final modelProvider =
StateNotifierProvider.autoDispose<ModelClassName, dynamic>(
(ref) => ModelClassName());
Related
I want to extend the Wso2 CEP product in our needs and try to write a custom condition as indicated in this official wso2 cep link.
I am able to write an extension class that extends "org.wso2.siddhi.core.executor.conditon.AbstractGenericConditionExecutor" and implement its abstract method as indicated below:
#SiddhiExtension(namespace = "myext", function = "startswithA")
public class StringUtils extends
org.wso2.siddhi.core.executor.conditon.AbstractGenericConditionExecutor {
static Log log = LogFactory.getLog(StringUtils.class);
#Override
public boolean execute(AtomicEvent atomicEvent) {
log.error("Entered the execute method");
log.error("Atomic event to string: " + atomicEvent.toString());
return true;
}
}
when i use this extensioned method as:
from allEventsStream[myext:startswithA(name)]
insert into selectedEventsStream *;
In this situation, i want that startswithA method returns true if the name field has 'A' at the begining of it. However when i run this query in CEP the whole event drops into my execute function i.e. there is no sign to show that i send "name" field is sent to startswithA method as argument.
How can i understand which field of the stream is sent to my extended method as argument?
Also i want to write conditions like
from allEventsStream[myext:startswith('A', name)]
insert into selectedEventsStream *;
How can i achive this?
In 'AbstractGenericConditionExecutor' there's another method that gives you the set of expression executors that are included in the parameters when executor instantiates:
public void setExpressionExecutors(List<ExpressionExecutor> expressionExecutors)
You don't necessarily have to override this method and store the list, it is already stored there in the 'AbastractGenericConditionExecutor' as a list named expressionExecutors. You can pass the event to these executors to retrieve the relevant values from the event in order.
For an example, if you include a variable (like 'name') in the query (as a parameter at index 0), you'll get a 'VariableExpressionExecutor' in the list at index 0 that will fetch you the value of the variable from the event. Similarly for a constant like 'A', you'll get a different executor that will give you the value 'A' when called.
To add to Rajeev's answer, if you want to filter all the names that starts with 'A', you can override the execute method of your custom Siddhi extension similar to the following segment.
#Override
public boolean execute(AtomicEvent atomicEvent) {
if(!this.expressionExecutors.isEmpty()) {
String name = (String)this.expressionExecutors.get(0).execute(atomicEvent);
if(name.startsWith("A")) {
return true;
}
}
return false;
}
When writing the query, it would be similar to
from allEventStream[myext:startsWithA(name)]
insert into filteredStream *;
You can extend this behaviour to achieve an extension that supports
from allEventsStream[myext:startswith('A', name)]
type queries as well.
HTH,
Lasantha
I use console.log() a lot, especially in combination with Ember.inspect(). But there's one thing I miss:
How can I find out the type of an object (Class)?
For example: Getting something like <Sandbox.ApplicationController:ember288> when inspecting Ember.get("controller")?
If you just want the model name (for example app/models/comment.js has the model name comment), you can use thing.constructor.modelName.
For example:
var aComment = this.get('store').createRecord('comment');
aComment.get('constructor.modelName') // => 'comment'
I understand you are looking for a string for debugging purposes, but I originally came to this question wanting to know specifically how to get the type of the object, not a string describing the object.
Using the built in Javascript property constructor will yield the class used to construct the instance. For example you could do:
person = App.Person.create();
person.constructor // returns App.Person
person.constructor.toString() // return "App.Person"
If you get Class, you can usually call toString() (or as a shortcut concat an empty string + '') to get something like <Sandbox.ApplicationController:ember288>
Another useful feature (in chrome) is the dir command.
dir(App.User)
This will give you the full object information, rather than just the name.
Be aware that some of these answers suggested here only work in development. Once your code is in production most of those methods / class names will get minified.
import Model from '#ember-data/model';
export default class Animal extends Model {
// ...
}
So in development:
const model = this.store.createRecord('animal');
model.constructor.name // returns Animal
in production:
const model = this.store.createRecord('animal');
model.constructor.name // returns 'i' (or any other single letter).
To avoid this, use constructor.toString()
const model = this.store.createRecord('animal');
model.constructor.toString() // returns 'model:animal'
I'd like to load 2 different input models (a .bpel and a .wsdl) in my main template of Acceleo.
I loaded the ecore metamodels for both bpel and wsdl and I'd like to be able to use something like this:
[comment encoding = UTF-8 /]
[module generate('http:///org/eclipse/bpel/model/bpel.ecore','http://www.eclipse.org/wsdl/2003/WSDL')/]
[import org::eclipse::acceleo::module::sample::files::processJavaFile /]
[template public generate(aProcess : Process, aDefinition : Definition)]
[comment #main /]
Process Name : [aProcess.name/]
Def Location : [aDefinition.location/]
[/template]
but when I run the acceleo template I get this error:
An internal error occurred during: "Launching Generate".
Could not find public template generate in module generate.
I think I have to modify the java launcher (generate.java) because right now it can't take 2 models as arguments. Do you know how?
Thanks!
** EDIT from Kellindil suggestions:
Just to know if I understood it right, before I get to modify stuff:
I'm trying to modify the Generate() constructor.
I changed it in:
//MODIFIED CODE
public Generate(URI modelURI, URI modelURI2, File targetFolder,
List<? extends Object> arguments) {
initialize(modelURI, targetFolder, arguments);
}
In the generic case, I can see it calls the AbstractAcceleoGenerator.initialize(URI, File, List>?>), shall I call it twice, once per each model? like:
initialize(modelURI, targetFolder, arguments);
initialize(modelURI2, targetFolder, arguments);
Then, to mimic in my Generate() constructor the code that is in the super-implementation:
//NON MODIFIED ACCELEO CODE
Map<String, String> AbstractAcceleoLauncher.generate(Monitor monitor) {
File target = getTargetFolder();
if (!target.exists() && !target.mkdirs()) {
throw new IOException("target directory " + target + " couldn't be created."); //$NON-NLS-1$ //$NON-NLS-2$
}
AcceleoService service = createAcceleoService();
String[] templateNames = getTemplateNames();
Map<String, String> result = new HashMap<String, String>();
for (int i = 0; i < templateNames.length; i++) {
result.putAll(service.doGenerate(getModule(), templateNames[i], getModel(), getArguments(),
target, monitor));
}
postGenerate(getModule().eResource().getResourceSet());
originalResources.clear();
return result;
}
what shall I do? Shall I try to mimic what this method is doing in my Generate() constructor after the initialize() calls?
What you wish to do is indeed possible with Acceleo, but it is not the "default" case that the generated launcher expects.
You'll have to mark the "generate" method of the generated java class as "#generated NOT" (or remove the "#generated" annotation from its javadoc altogether). In this method, what you need to do is mimic the behavior of the super-implementation (in AbstractAcceleoLauncher) does, loading two models instead of one and passing them on to AcceleoService#doGenerate.
In other words, you will need to look at the API Acceleo provides to generate code, and use it in the way that fits your need. Our generated java launcher and the AcceleoService class are there to provide an example that fits the general use case. Changing the behavior can be done by following these samples.
You should'nt need to modify the Generate.java class. By default, it should allow you to perform the code generation.
You need to create a launch config and provide the right arguments (process and definition) in this launch config, that's all.
I don't understand the 'client.xmi' URI that is the 1st argument of your module. It looks like it is your model file, if so remove it from the arguments, which must only contain your metamodels URIs.
I'm pretty new to scala and basically I want to have a couple of functions coupled to a string in a hashmap.
However I get an error at subscribers.get(e.key)(e.EventArgs); stating Option[EventArgs => Unit] does not take parameters...
Example code:
object Monitor {
val subscribers = HashMap.empty[String, (EventArgs) => Unit ]
def trigger(e : Event){
subscribers.get(e.key)(e.EventArgs);
}
def subscribe(key: String, e: (EventArgs) => Unit) {
subscribers += key -> e;
}
}
The get method of a Map gives you an Option of the value, not the value. Thus, if the key if found in the map, you get Some(value), if not, you get None. So you need to first "unroll" that option to make sure there is actually a value of a function which you can invoke (call apply on):
def trigger(e: Event): Unit =
subscribers.get(e.key).foreach(_.apply(e.EventArgs))
or
def trigger(e: Event): Unit =
subscribers.get(e.key) match {
case Some(value) => value(e.EventArgs)
case None =>
}
There are many posts around explaining Scala's Option type. For example this one or this one.
Also note Luigi's remark about using an immutable map (the default Map) with a var instead.
Since the get method returns Option, you can use 'map' on that:
subscribers.get(e.key).map(f => f(e.EventArgs))
or even shorter:
subscribers.get(e.key) map (_(e.EventArgs))
get only takes one argument. So subscribers.get(e.key) returns an Option, and you're trying to feed (e.EventArgs) to that Option's apply method (which doesn't exist).
Also, try making the subscribers a var (or choosing a mutable collection type). At the moment you have an immutable collection and an immutable variable, so your map cannot change. A more idiomatic way to declare it would be
var subscribers = Map[String, EventArgs => Unit]()
HashMap.get() in Scala works in a bit different way, than in Java. Instead of returning value itself, get() returns Option. Option is a special type, that can have 2 values - Some(x) and None. In first case it tells "there's some value with such a key in a map". In second case it tells "nope, there's nothing (none) for this key in a map". This is done to force programmers check whether map actually has an object or not and avoid NullPointerException, which appears so frequently in Java code.
So you need something like this:
def trigger(e: Event) {
val value = subscribers.get(e.key)
value match {
case None => throw new Exception("Oops, no such subscriber...")
case Some(f) => f(e.EventArgs)
}
}
You can find more info about Option type and pattern matching in Scala here.
How do I test which view was rendered from a controller action if what I get is a T4MVC_ActionResult? Under normal circumstances I should be able to directly use TestHelper's methods, like in the examples:
pooController.Details().AssertViewRendered().ForView("Details")
...but, since through T4MVC I get a T4MVC_ActionResult instead of a ViewResult, the part AssertViewRendered<>().ForView("Details") fails. What alternative do I have if I want to test which view was invoked?
UPDATE:
Here's the test code:
[TestMethod]
public void Theme_Controller_Details_Action_Returns_Details_View()
{
var builder = new TestControllerBuilder();
var mockThemeRepository = new Mock<IThemeRepository>();
var themeController = builder.CreateController<Evalgrid.Website.Controllers.ThemeController>(mockThemeRepository.Object);
builder.InitializeController(themeController);
var result = themeController.Details();
result.AssertViewRendered().ForView("Details");
}
I used the debugger setting a breakpoint after the result line, and its variable type is T4MVC_ActionResult, while themeController is Evalgrid.Website.controllers.ThemeController. Note that I have used the fully qualified name of the controller.
I get this:
Expected result to be of type
ViewResult. It is actually of type
T4MVC_ActionResult.
I don't know what's going on.
Actually, T4MVC should not make a difference here. If you directly instantiate your controller and call an action method, you'll get the same thing back whether you use T4MVC or not. i.e. you won't get a T4MVC_ActionResult.
It's only when you write MVC.Foo.Details() that you'll get a T4MVC_ActionResult. That's because MVC.Foo returns an instance of a derived class which does special thing, and not directly your controller class.
Does that make sense?
Update: I'm confused, as looking at the sources for TestControllerBuilder.CreateController, it has:
public T CreateController<T>(params object[] constructorArgs) where T : Controller
{
var controller = (Controller)Activator.CreateInstance(typeof(T), constructorArgs);
InitializeController(controller);
return controller as T;
}
So it's directly instantiating the type that you pass in, which should just call your normal action.
One question about your code: does your Details action method take any parameters? If so, that would explain the problem, as you're calling it with no params, which would be a T4MVC method added in the partial class.