I'm new in Scala (I come from Java) and I would like to know how is the correct way to generate documentation for the class variables.
For example, if I have the following code:
class MyClass (bar:bar) {
val foo = bar
def function {
...
...
}
}
what's the correct way to create the documentation for the variable foo ? Do I just add the comment right before the declaration? Isn't it a bit confusing?
Thanks!
You can use Javadoc in Scala. But Scala also introduces its own documentation generator called Scaladoc. This is what is used to generate the standard language documentation.
In general, Scaladoc follows similar conventions to Javadoc but introduces new features. You can read more about Scaladoc comments style here.
There is no difference between java and scala comments. You can choose any documentation strategy you used in java.
Related
I'm trying to find documentation of the Map.toList method in Scala but looking at documentation this is a trait : http://www.scala-lang.org/api/current/index.html#scala.collection.immutable.Map . So how can I find the documentation for scala Map? WHen I instatiate a Map am I just instantiating the trait ?
Trait scala.collection.immutable.Map is a contract. It's valid for all implementations, so its documentation is a documentation for any immutable scala Map.
In current implementation method Map.apply (Map(a -> b, c -> d, ...)) creates HashMap for more than 4 elements.
There are also classes Map1 - Map4 for 1-4 elements. Also there is a singleton EmptyMap.
But this behavior could be changed in next scala versions in case there will be better implementation for general purpose.
It is defined in Predef. Also its source might be useful.
Traits cannot be instantiated. They are abstract by definition. If they're actually fully implemented, they can (appear to) be instantiated by creating an anonymous type at the point of instantiation:
val x = new FullyImplementedTraitName { }
As to your main question, the documentation for scala.collection.Map should tell you everything you need to know. When you have the full frameset for the ScalaDocs displayed the filter text field at the upper left allows you to narrow down the class and package list by entering a the name (or portion thereof) you're looking for.
I'm at a loss on this one...
Looking at a Set in Scala collections, I see that there is a method called subsetOf. But when I try to find where it is in the actual .scala source code (I've looked in Set.scala, GenSet.scala, SetLike.scala etc...) I can't find it!!!
Which trait actually defines that method? Or am I missing something?
If you click on function in scaladoc, you may see where is it defined:
The scala API specifies:
Definition Classes: GenSetLike
When you're looking at the API page, click the method entry to expand it. You'll see more information, including the "Definition Classes".
If you look at the source for GenSetLike.scala, you'll see it:
def subsetOf(that: GenSet[A]): Boolean = this forall that
I'm trying to get a list of tokens (I'm most interested in keywords) and their positions for a given scala source file.
I think there is a lexer utility inside scala compiler, but I can't find it. Can you point me into the right direction?
A simple lexer for a Scala-like language is provided in a standard library.
A small utility program which tokenizes Scala source using the same lexer as compiler does lives here
Scalariform has an accurate Scala lexer you can use:
import scalariform.lexer._
val tokens = ScalaLexer.rawTokenise("class A", forgiveErrors = true)
val keywords = tokens.find(_.tokenType.isKeyword)
val comments = tokens.find(_.tokenType.isComment)
Parser Combinators might help in what you are trying to achieve here, especially if you later on are not only interessted in keyword parsing.
Consider something like this:
object Singleton
val cls: Class[Singleton] = ???
What do I have to write instead of ????
I tried classOf[Singleton], classOf[Singleton.type], Singleton.type, but nothing worked.
(I know of course about getClass, the runtime version of classOf, but that's not what I'm asking.)
Here a solution, but it's not pretty ...
object Singleton
val cls : Class[Singleton] = Singleton.getClass.asInstanceOf[Class[Singleton]]
Edit: completed the solution after reading another question/answer: Scala equivalent of Java java.lang.Class<T> Object
Note1: type erasure would prevent this from being particularly useful, e.g. in pattern matching. See referenced question/answer, above, for a good explanation
Note2: the scala -explaintypes flag is quite handy in understanding type errors.
HTH
You are not alone with this problem. The answer is: There is currently no way to avoid a Singleton.getClass. See this comment for more information why classOf[Singleton] does not work
Yes, I know it's considered lazy by the non-Pythonistas. The reason I ask is that documentation is still woefully lacking in many Scala libraries (e.g. Scala-dbc, but that's not all I'm looking at), and if I could see the attributes of an object/class at runtime, I could at least figure out what's available. Thanks.
Scala does not have a reflection API. The only way to access this information is to use the Java reflection API. This has the disadvantage that the structure may change as the way Scala is represented in Java classes and interfaces may change in the future.
scala> classOf[AnyRef].getMethods
res0: Array[java.lang.reflect.Method] = Array(public final void ...
Some specific type information that is present in the byte code can be accessed with the ScalaSigParser.
import tools.scalap.scalax.rules.scalasig._
import scala.runtime._
val scalaSig = ScalaSigParser.parse(classOf[RichDouble])
That's one of my main uses for REPL. Type the object's name, dot, and then TAB and it will show all available methods.
It isn't perfect. For one thing, it shows protected methods, which won't be available unless you are extending the class. For another thing, it doesn't show methods available through implicit conversion.
And, of course, the IDEs are all capable of doing that.
You might want something like the following which would give you what you need. In this case, it operates on a String, obviously.
val testStr = "Panda"
testStr.getClass.getMethods.foreach(println)
Does that work?
You may want to use this little helper to beef up the REPL