Also blogged here:
http://blog.headius.com/2009/03/more-compiling-ruby-to-java-types.html
Charles Oliver Nutter wrote:
I have committed another round of work on compiler2, and it now supports
signatures. Here's an example:
require 'rbconfig'
require 'java'
require 'tool/signature'
class MyRubyClass
def helloWorld
puts "Hello from Ruby"
end
def goodbyeWorld(a)
puts a
end
%w[boolean byte short char int long float double].each do |type|
java_type = Java.send type
eval "def #{type}Method(a); a; end"
signature "#{type}Method", [java_type] => java_type
end
def nevermore(*a)
a[0]
end
signature :helloWorld, [] => Java::void
signature :goodbyeWorld, [java.lang.String] => Java::void
end
The signature logic here is totally up for discussion; ultimately all
the compiler looks for is that the target class object (MyRubyClass in
this case) responds to a "signature" method, which it uses to look up
signatures. The signatures are simply a hash mapping a parameter list
(as an array) to a return type.
The above example defines several methods. First there's the obvious
helloWorld, goodbyeWorld and nevermore. helloWorld takes no parameters
and returns void. goodbyeWorld takes a java String and returns void.
nevermore does not have a signature definition, so it's all IRubyObject
on the way in and out.
More interesting are the *Method methods. The class definition iterates
over all Java primitive types, creating a method for each that accepts
and returns that type. And because compiler2 inspects *runtime* types,
it sees all these methods. Here's the command line again to compile this:
jruby -I ../bitescript/lib/ tool/compiler2.rb MyObject MyRubyClass myruby
And the resulting Java class file:
Compiled from "MyObject.java.rb"
public class MyObject extends org.jruby.RubyObject{
static {};
public MyObject();
public double doubleMethod(double);
public int intMethod(int);
public void helloWorld();
public char charMethod(char);
public long longMethod(long);
public byte byteMethod(byte);
public short shortMethod(short);
public boolean booleanMethod(boolean);
public org.jruby.runtime.builtin.IRubyObject
nevermore(org.jruby.runtime.builtin.IRubyObject[]);
public float floatMethod(float);
public void goodbyeWorld(java.lang.String);
}
In the non-signature case, nevermore, you see that it just accepts
IRubyObject[] and returns IRubyObject, so IRubyObject arguments will
just pass in and out without any coercion. In all the other cases, we
perform Java integration-style coercion on the way in and out.
There's more to come, but what we have right now is already checked into
trunk. Please, play with it!
- Charlie
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