Lets say I have the following interface:
interface MathThing {
fun mathFunction(x : Int)
}
Let's say the constraint I want to put onto this function is that x cannot be negative.
How can I make sure that every time this (or any other arbitrary) condition isn't met on a object of type MathThing, a (custom) exception is thrown?
One way is to use a wrapper class for your function parameters. You can make an extension function so it's a little easier to pass values to the function.
data class NonNegative(val value: Int) {
init{ if (value < 0) throw IllegalArgumentException("Input must not be negative.") }
}
fun Int.nonNegative() = NonNegative(this)
interface MathThing {
fun mathFunction(x : NonNegative)
}
Related
So, I have a Value Interface with these array field getter and setter methods, which works
interface Instrument: Marshallable {
...
fun setBidAt(index: Int, entry: OrderBookEntry)
#Array(length = 10)
fun getBidAt(index: Int): OrderBookEntry
}
interface OrderBookEntry: Marshallable{
var level: Int
var quantity: Long
var price: Double
var orders: Long
var side: OrderBookSide
}
However, I want a getter and setter that interact with the whole Array, something like:
interface Instrument: Marshallable {
...
fun setBids(entries: kotlin.Array<OrderBookEntry>)
#Array(length = 20)
fun getBids(): kotlin.Array<OrderBookEntry>
}
but as expected encountered some exceptions:
java.lang.IllegalStateException: bids field type class [Lme.oms.instrument.OrderBookEntry; is not supported: not a primitive, enum, CharSequence or another value interface
Now, does this mean that I can't leverage Chronicle Value Interface and have to create a custom class to achieve this? I have tried to look in both ChronicleValues and ChronicleMap test cases, seems like there is no test for this scenario?
EDIT: I managed to find a workaround by leveraging kotlin's extension function:
fun Instrument.getAsks(): kotlin.Array<OrderBookEntry>{
val array = arrayOf<OrderBookEntry>()
for (i in (0 until OrderBookMaxSize)) {
array[i] = getAskAt(i)
}
return array
}
If you use an interface via the values module, the elements of the array also need to be values so they can be flyweights as well. Without this information, it can't determine how large the elements of the array will be.
I am an ex python dev sometimes struggling with the explicit nature of Go.
I am trying here to refactor some code in order to be able move a method from one structure to be part of an interface.
But the process seems weird to me, I wish to confirm I am not doing something incorrectly.
I have the following interfaces, structure and methods:
type Executing interface {
Execute()
}
type MyExecuter struct {
attribut1 string
}
//The function I wish to move
func (exe1 *MyExecuter) format() string {
return fmt.sprintf ("formated : %s", exe1.attribut1)
}
func (exe1 *MyExecuter) Execute() {
//Executing
fmt.Println(exe.format())
}
func GetExecuter () Executer{
return MyExecuter{attribut1: "test"}
}
So here I have a generic interface Execute, this interface will be accessed by the object returned by the GetExecuter method.
Now, as part of the implementation of one of my Executer, I want to move the Format method as part of an interface.
So I am doing the following:
type Formatting interface {
format() string
}
type Formatter struct {}
func (formatter *Formatter) format(exe1 *MyExecuter) (string) {
return fmt.sprintf ("formated : %s", exe1.attribut1)
}
So I create a new interface, a new empty structure, and update my function to take as attribute my previous structure.
While this seems to work, it seems to me this is a bit convoluted. Specially the part where I need to add a reference to my initial object as attribute of the method. Am I doing something wrong here, or this is the right way?
Your Executer implementation already implements the Formatting interface:
type Executing interface {
Execute()
}
type Formatting interface {
format() string
}
func (exe1 MyExecuter) format() string {
return fmt.sprintf ("formated : %s", exe1.attribut1)
}
func (exe1 MyExecuter) Execute() {
//Executing
fmt.Println(exe.format())
}
v:=MyExecuter{}
// Here, v implements Executing and Formatting interfaces
One thing to note here: Your code shows pointer receivers. That means the methods are defined for *MyExecuter, but not for MyExecuter. So you have to pass pointers to the struct instance for this to work. Or, as I did above, use the value receivers so the methods are defined for both MyExecuter and *MyExecuter.
I'm using Kotlin reflection to check if attributes that have a certain annotation are null.
Given the following example:
data class DataClass(
#SomeRandomAnnotation
val otherAnnotated: String?,
val inner: InnerClass
)
data class AnotherDataClass(
#SomeRandomAnnotation
val annotatedProperty: String?,
val dataClass: DataClass
) {
fun checkCreditAnalysisConstrain() {
print(checkConstrain(this))
}
}
And the function that checks it:
fun checkConstrain(parentClass: Any): List<String> {
val filter = parentClass::class.memberProperties.filter {
if (memberIsDataClass(it)) checkConstrain(getMemberPropertyInstance(parentClass, it))
hasAnnotation(it) && propertyIsNull(it, parentClass)
}
return filter.map { formatResult(parentClass, it) }
}
The idea is that the function is going to iterate through the attributes of my classes checking if they have the annotation and checking if the value is null.
If the property is a data class, the code evaluates the properties of the childs, recursively.
After that, I map the results, transforming the KProperty's into a simple String that is human readable, containing the class name and the attribute name.
The problem is that the above code does not work as expected. The properties returned are only the properties from the first-level class.
If, instead of doing a filter, I just run a forEach and print the result, I get the expected attributes. So I'm pretty sure it's related to the recurring inside a filter.
Do you see any way of doing this in a more functional way? I'm just concerned I won't need a "temp" list and add values to the list and reset it afterwards.
Your function recursively calls itself, but does nothing with the returned list of that recursive call. That's why you only get results for the top-level class.
Also, in my opinion, you shouldn't rely on side effects happening from your filter call. It probably works, but the function's documentation does not provide a guarantee that it will be called exactly once per item in the collection. So there should be a separate for-loop to do the recursive calls, and the result should be added onto existing results.
fun checkConstrain(parent: Any): List<String> {
val memberProperties = parent::class.memberProperties
var result = memberProperties
.filter { hasAnnotation(it) && propertyIsNull(it, parent) }
.map { formatResult(parent, it) }
memberProperties.filter { memberIsDataClass(it) }
.mapNotNull { getMemberPropertyInstance(parent, it) }
.forEach { result += checkConstrain(it) }
return result
}
You didn't provide code for several of the functions you used. This is what I used for them:
val KProperty<*>.returnTypeClass get() = this.returnType.classifier as? KClass<*>
fun <T> memberIsDataClass(member: KProperty<T>) = member.returnTypeClass?.isData == true
fun <T> getMemberPropertyInstance(parent: Any, property: KProperty<T>) = property.getter.call(parent)
fun <T> hasAnnotation(property: KProperty<T>) = property.annotations.firstOrNull { it.annotationClass == SomeRandomAnnotation::class } != null
fun <T> propertyIsNull(property: KProperty<T>, parent: Any) = getMemberPropertyInstance(parent, property) == null
fun formatResult(parent: Any, property: KProperty<*>) = "$parent's property(${property.name}) is annotated with SomeRandomAnnotation and is null."
How can I test an extension function with Mockito? It doesn't seem to work nicely.
This is my extension function
fun <T> CrudRepository<T, String>.findOneById(id: String): T? {
val o = findById(id)
return if (o.isPresent) o.get() else null
}
And this is what I'm trying to test
#Test
fun getIslandById() {
//given
BDDMockito.given(islandRepository.findOneById("islandId1"))
.willReturn(IslandEntity(tileList, "1", "islandId1")) //findOneById is my extension function
//when
val island = islandService.getIslandById("islandId1")
//then
Assertions.assertThat(island?.id).isEqualTo("islandId1")
}
But the preceeding test throws the following error
org.mockito.exceptions.misusing.WrongTypeOfReturnValue:
IslandEntity cannot be returned by findById()
findById() should return Optional
Any ideas?
Instance extension functions can be mocked like this with a little help of mockito-kotlin:
data class Bar(thing: Int)
class Foo {
fun Bar.bla(anotherThing: Int): Int { ... }
}
val bar = Bar(thing = 1)
val foo = mock<Foo>()
with(foo) {
whenever(any<Bar>().bla(any()).doReturn(3)
}
verify(foo).apply {
bar.bla(anotherThing = 2)
}
As I said in a comment above, in the bytecode extension functions are nothing more than static functions which accept receiver as a first argument. Therefore you can't mock an extension function with a Mockito since it is not able to mock static functions.
What you can do, in case that findById(id) is implemented by Repository and not another extension function, is next:
Mock return value of findById(id) instead.
Take a look at the sample code below:
#Test
fun getIslandById() {
//given
BDDMockito.given(islandRepository.findById("islandId1"))
.willReturn(Optional.of(IslandEntity(tileList, "1", "islandId1"))) //mock findById function
//when
val island = islandService.getIslandById("islandId1")
//then
Assertions.assertThat(island?.id).isEqualTo("islandId1")
}
This way you are indirectly mocking your extension by providing it a mocked value that you want it to operate on.
Note: Error that you posted above says that your findById(id) should return an optional. So, wrap your return value of findById(id) function with an optional by calling Optional.of(result).
Considering the given code:
val repository =
context.getBean(
Introspector.decapitalize(t.getClass.getSimpleName).replace("C", "E").concat("Repository"))
and that my repositories have a String as Serializable.
I'm trying to do the following:
repository.asInstanceOf[ElasticsearchRepository[_, String]].save(getObject(t))
This one works fine:
repository.asInstanceOf[ElasticsearchRepository[_, String]].findAll()
But I don't know how to put that above to work.
Assuming the method getObject(t) is retuning the correct object to be persisted and since it's a Spring Data Repository, there are 2 save method. One that accept a single entity and another for a list of entities and it says overloaded method value save.
What I have tried so far:
I saw in another thread to force the method with a type, something like this:
repository.asInstanceOf[ElasticsearchRepository[_, String]].save(getObject(t) : TYPE)
This is ok if I knew the type and also my method getObject should return that same type.
Here is my getObject method which I return the object itself without any specific type:
#throws[IOException]
def getObject[T](t : T) = {
objectMapper.readValue(objectMapper.writeValueAsString(t), getClazz(t))
}
So I was trying to get the type like this:
val m = Manifest.classType(getClazz(t))
type TYPE = m.type
Looks good if I force my object to this type using getObject(t) : TYPE but I don't know how to use this same type in my getObject method to be returned.
Anyway, I don't even know if this is the best approach to do this, invoking a generic repository and save a generic object.
Just to understand what I'm trying to do, I'm using a aspect to intercept a Cassandra entity to be persisted, then get it and turn into a ElasticSearch entity to save a json(thats why the getObject(t)) and replicate into ElasticSearch.
Here is the full aspect class:
#Component
#Aspect
class ElasticAop {
#Autowired val context : ApplicationContext = null
val objectMapper : ObjectMapper = new ObjectMapper()
#Pointcut("execution(* com.test.service.cassandra.*.post(..)) && args(t)")
def getPointcutPost[T](t : T) : Unit = {}
#throws[Throwable]
#Before("getPointcutPost(t)")
def elasticSaveAspect[T](joinPoint: JoinPoint, t: T) = {
val m = Manifest.classType(getClazz(t))
type TYPE = m.type
val repository =
context.getBean(
Introspector.decapitalize(t.getClass.getSimpleName).replace("C", "E").concat("Repository"))
repository.asInstanceOf[ElasticsearchRepository[_, String]].findAll()
repository.asInstanceOf[ElasticsearchRepository[_, String]].save(getObject(t))
}
#throws[ClassNotFoundException]
def getClazz[T](t : T) = {
val className = t.getClass.getName.replace("cassandra", "elastic").replace("C", "E")
Class.forName(className)
}
#throws[IOException]
def getObject[T](t : T) = {
objectMapper.readValue(objectMapper.writeValueAsString(t), getClazz(t))
}
}
EDITED
Even setting up a type return in my getObject to Address and then setting the save method as follow save(getObject(t) : Address) give me the same overloaded error.
EDITED
I just figured out it's a limitation and a possible work around is to create a factory or something like this.
Then I created a service with a saveOrUpdate method:
trait ElasticGenericService[T <: ElasticGenericKey, R <: ElasticsearchRepository[T, String]] {
var r : R = _
def saveOrUpdate(t: T) = r.save(t)
}
and now I'm getting a cast exception:
java.lang.ClassCastException: Address cannot be cast to scala.runtime.Nothing$
What i can see here:
getObject[T](t : T) returns existential type _1 and actually kills all type checks, as you choosing the class in runtime
ElasticsearchRepository[_, String].save require existential type _2 to be passed to the save method, so _1 doesn't fit
Possible solution:
repository.asInstanceOf[ElasticsearchRepository[Any, String]].save(getObject(t).asInstanceOf[Any]) //getClass will work with runtime class instead of Any, so should be fine
Another solution (saving existential type):
def getObject[T](t : T) = {
objectMapper.readValue(objectMapper.writeValueAsString(t), getClazz(t)).asInstanceOf[T]
} //assuming T is an existential - it will return same existential as you passed