I'm trying to use code for a school assignment, and I copied the professors outline like we were supposed to but one of the lines is causing an error in my ide saying missing arguments for method apply in object List; the line of code is
private var d = List[(String,Any)]
and I really don't understand what is wrong with it?
You need parens after the type to actually create the empty list:
private var d = List[(String,Any)]()
or alternatively:
private var d = List.empty[(String,Any)]
Related
Hi this is my first time making a question so hopefully i have done this right :)
In my code Im trying to make a Arraylist that is within a class that only holds floats so I made this: (some information is taken away to make it easier to read)
class object {
private ArrayList yc=new ArrayList<Float>();
private ArrayList xc=new ArrayList<Float>();
object(float xer,float yer,float rer){
xc.add(10.0);
x=xer;
y=yer;
r=rer;
}
void update(){
print(xc.get(0))
x=xc.get(0);
}
}
everything else except x=xc.get(0) works outside of the class this assignment works but inside the class it doesn't
hope this makes sense thanks.
It seems like when you initialised the variable xc you specified the type of the ArrayList to Float. However, when declaring xc, you did not specify the type.
When you try to assign variable x with xc.get(0), you are basically assigning any Object to variable x that was declared as a Float.
To solve this issue you can declare your variable xc specifying the type of the ArrayList: private ArrayList<Float> xc = new ArrayList<Float>();
Also, processing offers the helper class FloatList as well if this suits your program.
This should solve your issue, depending on the rest of your code.
I get an error when I put the type and size of an array of classes
I have tried:
fun main(args :Array<String>) {
class modul() {
var nommodul: String? = null
var coeff: Int? = null
var note: Int? = null
}
var releve
class notes() {
var releve: array<modul>(10){""} here the erreur
}
}
First of all, your code has several errors. This might be an MCVE and/or copy-paste issue, but I need to address these before I get started on the arrays.
var releve before the notes class isn't allowed. You don't assign it, you don't declare a type, and the compiler will complain if you copy-paste the code from your question.
Second, the array var itself: Array is upper-case, and initialization is separate. This would be more valid (note that this still does not work - the solution for that comes later in this answer):
var releve: Array<modul> = Array(10) {...}
// or
var releve = Array<modul>(10) {...}
And the last thing before I start on the array itself: please read the language conventions, especially the naming ones. Your classes should all start with an upper-case letter.
Kotlin arrays are quite different from Java arrays in many ways, but the most notable one being that direct array initialization also requires an initializer.
The brackets are expected to create a new instance, which you don't. You create a String, which isn't, in your case, a modul.
There are several ways to fix this depending on how you want to do this.
If you have instances you want to add to the array, you can use arrayOf:
arrayOf(modulInstance, modulInstance2, ...)
If you want to create them directly, you can use your approach:
var releve = Array(10) { modul() }
A note about both of these: because of the initialization, you get automatic type inference and don't need to explicitly declare <modul>
If you want Java-style arrays, you need an array of nulls.
There's two ways to do this:
var releve = arrayOfNulls<modul>(10)
// or
var releve = Array<modul?>(10) { null }
I highly recommend the first one, because it's cleaner. I'm not sure if there's a difference performance-wise though.
Note that this does infer a nullable type to the array, but it lets you work with arrays in a similar way to Java. Initialization from this point is just like Java: releve[i] = modul(). This approach is mostly useful if you have arguments you want to add to each of the classes and you need to do so manually. Using the manual initializers also provides you with an index (see the documentation) which you can use while initializing.
Note that if you're using a for loop to initialize, you can use Array(10) { YourClass() } as well, and use the supplied index if you need any index-sensitive information, such as function arguments. There's of course nothing wrong with using a for loop, but it can be cleaner.
Further reading
Array
Lambdas
here some example of kotlin array initialization:
array of Library Method
val strings = arrayOf("January", "February", "March")
Primitive Arrays
val numbers: IntArray = intArrayOf(10, 20, 30, 40, 50)
Late Initialization with Indices
val array = arrayOfNulls<Number>(5)
for (i in array.indices) {
array[i] = i * i
}
See Kotlin - Basic Types for details
My code looks like:
case class SRecord(trialId: String, private var _max:Int) {
def max=_max
def max_=(value:Int):Unit=_max=value
}
Then later on I apply a function onto it:
def groupSummaryRecords(it:Iterator[Option[SRecord]], optionSummary:Option[SRecord]):Option[SRecord] = {
var max=0;
var sRecord1 : Option[SRecord] = None
var i=0
while(it.hasNext) {
var sRecord:Option[SRecord] = it.next();
if(i==0) {
sRecord1 = sRecord;
}
..
}
sRecord1.max=max; // getting 'reassignment to val' compilation error
..
}
Why am i getting this compilation error, and how to fix it ?
If I instead change sRecord and sRecord1 instances to be of type SRecord instead of Option[SRecord] as well as the method signature, it all works fine however.
But in some cases I may have a null SRecord hence the use of None/Some. I am new to Scala, using Option/Some all over feels like a real pain if you ask me, i am just thinking of removing all this Option nonsense and testing for 'null' in good ol' Java, at least my code would work ??!
With the line sRecord1.max=max you are trying to call the max method on an Option[SRecord], not an SRecord. You want to access the contained SRecord (if any) and call the method on that, which can be done using foreach:
sRecord1.foreach(_.max=max)
which is desugared to:
sRecord1.foreach( srec => srec.max=max )
(the actual name "srec" is made up, the compiler will assign some internal name, but you get the idea). If sRecord1 is None, this won't do anything, but if it is Some(srec), the method execution will be passed in to operate on the contained instance.
I'm trying to use Drools with Scala and i would like to know if it is possible to call a chain of events and create var/val when the function has a return.
Here is what i'm trying but i'm stuck:
import com.models.*
import com.service.*
rule "First Fule"
when
person:Person(name == 'aa')
then
//Here should return a string
//and i should set this string
//something like:
//var x = new Person(ServiceLongDong.sayHello(), person.age, person.name)
//or var y = ServiceLongDong.sayHello();
ServiceLongDong.sayHello();
ServiceLongDong.finish(x);
end
Is possible to create varl/vals and pass it to another function?
Thank in advance.
Rules aren't functions (or methods) and don't "return" values or objects. The right hand side is just Java code. You can call static methods, but stick to correct Java syntax:
Person p = new Person(ServiceLongDong.sayHello(),
person.age, person.name);
ServiceLongDong.sayHello();
ServiceLongDong.finish(x);
This can't be correct Java if ServiceLongDong is a class:
... = ServiceLongDong().sayHello();
Can someone explain the difference in Javascript between:
var x = something
and
var x : something
I have no idea on where/how to search about it.
I saw the code above at the bottom of page 4 of this document: http://download.unity3d.com/support/Tutorials/2%20-%20Scripting%20Tutorial.pdf
Thanks in advance!
The first one assigns something to a variable x and the other causes a syntax error.
You're probably mixing up assigning a property in an object literal and normal assignment.
var x = something;//assigning a variable
var y = {
x:something//assigning a object property
};
Edit
var target : Transform;
seems to be UnityScript not JavaScript, it looks like it is not assigning a value but rather setting the variable type. see here
UnityScript is not JavaScript
Unity Script vs Javascript
If you're defining vars in an object, you'd use colons.
var obj = {x:my_var};