I have got three classes:
class A {
//Duration in seconds
private val durationProperty = SimpleLongProperty(300)
var duration by durationProperty
}
class B(list: List<A>) {
private val aClassesProperty = SimpleListProperty(list.observable())
val aClasses by aClassesProperty
}
class C(classB: B, repetitions: Int){
private val bClassProperty = SimpleObjectProperty(classB)
private val repetitionsProperty = SimpleIntProperty(repetitions)
val repetitions by repetitionsProperty
}
Now I would like, to create and bind durationProperty inside class B as sum of class A durationProperty (which will be sensitive to adding new class A instance into list and changing any duration of already present instance) and similarly in class C - durationProperty as duration of classB multiplied by repetitions.
I don't know kotlin, but the answer should be easy to translate.
You need to use an 'extractor' to handle this, using:
FXCollections#observableArrayList(Callback<E, Observable[]> extractor)
Like:
ObservableList<A> list = FXCollections.observableArrayList(item -> new Observable[] {item.durationProperty});
list.addListener((InvalidationListener) observable -> {
//Update you sum here
});
The extractor causes any changes to the given observable array of each item in the list to trigger both the InvalidationListener and ListChangeListener of the list to be fired.
SephB's solution is correct, but finally I used one from there. I found it a little bit more elastic even though there is a lot of boilerplate.
Related
I am new with Axon and maybe I missed something, but need help to understand.
I have a simple food cart aggregate.
Here is example:
#Aggregate
class FoodCard {
#AggregateIdentifier
private lateinit var foodCardId: UUID
private lateinit var selectedProduct: MutableMap<UUID, Int>
constructor()
#CommandHandler
constructor(command: CreateFoodCartCommand) {
AggregateLifecycle.apply(FoodCartCreateEvent(
UUID.randomUUID()
))
}
#CommandHandler
fun handle(command: SelectProductCommand) {
AggregateLifecycle
.apply(ProductSelectedEvent(foodCardId, command.productId, command.quantity))
}
#CommandHandler
fun handle(command: DeleteFoodCartCommand) {
AggregateLifecycle
.apply(FoodCartDeleteEvent(foodCardId))
}
#CommandHandler
fun handle(command: DeselectProductCommand) {
val productId = command.productId
if (!selectedProduct.containsKey(productId)) {
throw ProductDeselectionException("ProductDeselectionException")
}
AggregateLifecycle
.apply(ProductDeselectEvent(foodCardId, productId, command.quantity))
}
#EventSourcingHandler
fun on(event: FoodCartCreateEvent) {
foodCardId = event.foodCardId
selectedProduct = mutableMapOf()
}
#EventSourcingHandler
fun on(event: ProductSelectedEvent) {
selectedProduct.merge(
event.productId,
event.quantity
) {a, b -> a + b}
}
}
As ES I am using Axon Server.
For FoodCard projector I am using JPA repository that connects to DB.
I want to get all foodcards that contain special product (concrete UUID) and change quantity to -1 for all of them.
I understood there are two types of actions -> read and write
So the question how to correctly implement this flow with Axon?
Thanks
from your explanation and code I feel that you will probably need to complete your implementation of DeselectProductCommand introducing an EventSourcingHandler for ProductDeselectEvent. If I understood correctly your "quantity" information is stored into the selectProduct Map. In this case, based on your code, I see that the information of the quantity that should be subtracted to your product is in the command.
You will also need a Query, such as FindAllFoodCardByProductId, that will retrieve the foodCardId aggregate identifier that contains a certain productId: this operation will be performed on your Projection through the jpa repository.
As a reference you can have a look at the ref guide here https://docs.axoniq.io/reference-guide/implementing-domain-logic/query-handling on how to use QueryGateway into your controller and implement a QueryHandler into your Projection.
Corrado.
I am trying to get a class to have a property bound to another class's list property, where the 1st property is derived from a summarizing calculation over the objects in the list. The code below is a simplified version of my production code. (The production code is doing a summary over DateTime objects -- the essential part of the code below is the binding between a list and an object property (here, it is a String for simplicity).)
I have tried various things. One approach was using addListener on the list in the Summary class below but I was running into weird bugs with the listener callback making updates on the Summary object. After doing a bunch of reading I think that a binding between the summary string and the list is more appropriate but I don't know exactly how to hook up the binding to the property?
package com.example.demo.view
import javafx.beans.Observable
import javafx.beans.binding.StringBinding
import javafx.beans.property.SimpleIntegerProperty
import javafx.beans.property.SimpleListProperty
import javafx.beans.property.SimpleStringProperty
import javafx.collections.FXCollections
import tornadofx.View
import tornadofx.button
import tornadofx.label
import tornadofx.vbox
class Thing(x: Int) {
val xProperty = SimpleIntegerProperty(x)
val yProperty = SimpleStringProperty("xyz")
}
class Collection {
private var things = FXCollections.observableList(mutableListOf<Thing>()) {
arrayOf<Observable>(it.xProperty)
}
val thingsProperty = SimpleListProperty<Thing>(things)
fun addThing(thing: Thing) {
things.add(thing)
}
}
class Summary(var collection: Collection) {
val summaryBinding = object : StringBinding() {
// The real code is more practical but
// this is just a minimal example.
override fun computeValue(): String {
val sum = collection.thingsProperty.value
.map { it.xProperty.value }
.fold(0, { total, next -> total + next })
return "There are $sum things."
}
}
// How to make this property update when collection changes?
val summaryProperty = SimpleStringProperty("There are ? things.")
}
class MainView : View() {
val summary = Summary(Collection())
override val root = vbox {
label(summary.summaryProperty)
button("Add Thing") {
summary.collection.addThing(Thing(5))
}
}
}
Keep in mind that I made this answer based on your minimal example:
class Thing(x: Int) {
val xProperty = SimpleIntegerProperty(x)
var x by xProperty
val yProperty = SimpleStringProperty("xyz")
var y by yProperty
}
class MainView : View() {
val things = FXCollections.observableList(mutableListOf<Thing>()) {
arrayOf<Observable>(it.xProperty)
}
val thingsProperty = SimpleListProperty<Thing>(things)
val totalBinding = integerBinding(listProperty) {
value.map { it.x }.fold(0, { total, next -> total + next })
}
val phraseBinding = stringBinding(totalBinding) { "There are $value things." }
override val root = vbox {
label(phraseBinding)
button("Add Thing") {
action {
list.add(Thing(5))
}
}
}
}
I removed your other classes because I didn't see a reason for them based on the example. If the collection class has more functionality than holding a list property in your real project, then add just add it back in. If not, then there's no reason to give a list its own class. The summary class is really just two bindings (or one if you have no need to separate the total from the phrase). I don't see the need to give them their own class either unless you plan on using them in multiple views.
I think your biggest problem is that you didn't wrap your button's action in action {}. So your code just added a Thing(5) on init and had no action set.
P.S. The var x by xProperty stuff will only work if you import tornadofx.* for that file.
How to transform a List into a new List by excluding a property in T.
For instance if User data class has 10 properties, I need to transform List into a new List without one particular property in User . New List like List
data class User(val name: String, val age: Int)
var userList = mutableListOf<User>()
var nameList= userList.map { it.name }
If a List to be created without property 'age'. Like
var withoutAgeList
In your first example:
var userList = mutableListOf<User>()
var nameList= userList.map { it.name }
The question "What's the type of nameList?" has a simple answer: List<String>. So let me ask you a similar question: What's the type of withoutAgeList? The answer to that question informs the answer to your question.
Perhaps a user without the age property is a separate AgelessUser class, meaning withoutAgeList is of type List<AgelessUser>. In that case, I suggest either a constructor or a factory function that builds AgelessUser from User, and you want one of these:
val withoutAgeList = userList.map { AgelessUser(it) } // constructor
val withoutAgeList = userList.map { agelessUserOf(it) } // factory
Alternatively, maybe the age property in User is nullable and immutable, and you want to represent users without an age as a regular User where age=null. In this case, you could copy the Users and override the age field
// TODO: pass all the other fields too
val withoutAgeList = userList.map { User(it.name, null) }
Assuming Users is a data class, we can avoid explicitly naming all fields by making use of copy():
val withoutAgeList = userList.map { it.copy(age = null) }
Maybe the age property is nullable and mutable — and you actually want to change the users in place instead of copying them. This is somewhat risky and I don't advocate doing it this way unless you really know what you're doing though.
userList.forEach { it.age = null }
// They're actually the same list!
val withoutAgeList = userList
In such a simple case you can map a list of Users into a list of strings:
val names: List<String> = userList.map(User::name)
Or you can declare a DTO and map into the latter:
class UserWithoutAge(val name: String)
val usersWithoutAge: List<UserWithoutAge> = userList.map { UserWithoutAge(it.name) }
P.S. you don't have to write an explicit type
You can use the Object Oriented approach:
data class User(val name: String, val age: Int)
data class UserNoAge(var name: String) {
constructor(user: User) : this(user.name)
}
var userList = listOf(User("John", 25), User("Jane", 30))
var userNoAge: List<UserNoAge> = mutableListOf<UserNoAge>()
userNoAge = userList.map{ UserNoAge(it) }
println(userNoAge) // [UserNoAge(name=John), UserNoAge(name=Jane)]
I have two table rows at an HTML file. When the first row gets clicked, it changes its styling via classes.add("active_style"). If the second row gets clicked, I would like to clear the first row styling.
I know that I can just write...
querySelector("#first_row_div").classes.clear();
... in order to clear the first row class (and then resetting its style), but in a bigger code I think that observable would be the best fit.
I don't know if observable works for this. But, if it does, how can I do that?
EDIT/UPDATE: I think that the right question is "is there any way to run a function when a variable gets changed?".
Thanks for the help!
You can make a getter/setter for a field and run your function in the setter.
class MyClass {
String _cssClass;
String get cssClass => _cssClass;
set cssClass(String newClass) {
_cssClass = newClass;
updateDom();
}
void updateDom() {
// do important work here
}
}
You can use a model class that extends Observable.
Here you have to call dirtyCheck() to make Observable check for changes and notify listeners.
Dart also offers the ChangeNotifier mixin. Here you don't need to call any method for dirty-checking. When changes are made listeners are invoked.
A simple example I wrote a while ago while examining the functionality
import 'package:observe/observe.dart';
class Notifiable extends Object with ChangeNotifier {
String _input = '';
#reflectable
get input => _input;
#reflectable
set input(val) {
_input = notifyPropertyChange(#input, _input, val + " new");
}
Notifiable() {
this.changes.listen((List<ChangeRecord> record) => record.forEach(print));
}
}
class MyObservable extends Observable {
#observable
String counter = '';
MyObservable() {
this.changes.listen((List<ChangeRecord> record) => record.forEach(print));
}
}
void main() {
var x = new MyObservable();
x.counter = "hallo";
Observable.dirtyCheck();
Notifiable notifiable = new Notifiable();
notifiable.input = 'xxx';
notifiable.input = 'yyy';
}
I have a bunch of variables in a class. There are situations when I want to set then to null/ "temp" etc as per a well defined logic. The challenge is to list out the variables at multiple places- tedious and error-prone.
classname.speed=NaN
classname.speedtype="not_set"
classname.distance=NaN
classname.distancetype="not_set"
Ideally, would prefer a way to refer to these variables programatically and set something like
"for all class variables- if variable ends in type, set as "not_set"; for other variables set as NaN
How can I achieve this? Any pointers will help
The simplest approach would be just write function to clear them all.
If you want something more automatic, it will requre efforts - look at introspection api. Basically, you call describeType on your class and it returns XML description. All variables will be listed there, along with other info. Then you can parse returned XML and set all variables to needed value, accessing them dynamically with square bracket syntax:
var myClass:MyClass = new MyClass();
myClass["varName"] = "new value";
It can be achieved through Inheritance i.e. implementing interface or extending class
which contains common fields
public class MyClass
{
public a:String = null;
public b:String = null;
public function MyClass()
{
}
}
which contains common var and Child Class could be
public class MyClassChild extends MyClass
{
public var c:String = null;
public function MyClassChild()
{
super();
this.a ="";
this.b ="";
}
}
and you can cast or use for each loop to set values
var temp:MyClassChild = new MyClassChild ();
MyClass(temp).a = "Hello World";
Hopes that helps