I'm trying to use classes and reference them within each other. Unfortunately I can't seem to figure it out how. What I try to do is:
Create a module exporting classes in different files. One of the classes has a method which returns another class.
Import the module in another class and make use of the classes from the module.
What I tried (simplified example):
Item.ps1
class Item {
}
ItemList.ps1
. '.\Item.ps1'
class ItemList {
[Item] function Items () {
// It goes wrong here. Visual studio code mentions type Item cannot be found.
}
}
Utilities.psm1
. '.\Item.ps1'
. '.\ItemList.ps1'
// I'm not sure if this is the right way to export the classes via the module
Foo.ps1
using module '.\Utilities.psm1'
class Foo {
[ItemList] function CreateItemList() {
// It goes wrong here. Visual studio code mentions type ItemList cannot be found.
}
}
I would really appreciate if some could help me figure this out!
Update
It looks like it can't be done. Here the following is mentioned:
In this release, you can't use a type literal (for example, [MyClass]) outside the script/module file in which the class is defined.
I am using Xtext do define a new language. I wish to generate code from this language, however I do not want to use the automatically suggested doGenerate function. Instead, I need to use a java code (not Xtend), that I can call from the build process.
Of course in that java code I want to be able to use the 'resource' that is passed to the original suggested function, so I can access all the information from the DSL's code.
I Believe by default the generator is implementation is an xtend file but there is nothing stopping you from changing this to a java file, you just need to override the binding in your [LanguageName]RuntimeModule class as follows:-
public class ExampleRuntimeModule extends com.example.AbstractExampleRuntimeModule {
#Override
public Class<? extends IGenerator> bindIGenerator() {
return YourOwnGenerator.class;
}
}
Where YourOwnGenerator should implement IGenerator.
I know that in AS3 I can create a Main class and link it to the FLA file. I tried doing the same in AS2 but couldn't. (When I try linking the fla to a class, it says the feature only exists in AS3)
Can I link the FLA to a class in some other way? If this is not possible, how would you suggest I perform actions when the file is loaded (and, in this case, define an ExternalInterface)?
Thank you.
here is the approach i would use. you define a static method in your 'document' class and then pass in the reference to your main timeline at runtime:
class MyClass extends MovieClip
{
public static function main(target:MovieClip):Void
{
target.__proto__ = MyClass.prototype;
target.init();
}
private function init():Void
{
// your construction code....
}
}
Then in your FLA, on the first frame, invoke the class's static 'main' and pass it the main timeline movieclip as the argurment. this is kinda like wrapping the timline with your document class.
MyClass.main(this);
Example based on http://www.bit-101.com/blog/?p=857. i just added it here to fix up the broken code tags on his site.
In a Groovy script is it possible to do a conditional import statement?
if (test){
import this.package.class
} else {
import that.package.class
}
The background to this is wanting to use something on MacOS 10.5 which only has JDK1.5 so one specific class is unavailable, but I have found someone who has written a back-port for it.
There is no way to conditionally import a class, but you can achieve something similar by attempting to load the class and then load another class if that one is not found.
Here's just an example:
def someClass
try {
someClass = "org.apache.webdavlib.WebdavFile" as Class
} catch (Exception ex) {
someClass = "java.io.File" as Class
}
def someInstance = someClass.newInstance("~/project/temp.log")
assert "java.io.File" == someInstance.getClass().getName()
Jochen "blackdrag" Theodorou proposed the following on the groovy user list a while ago:
wsh = this.class.classLoader.loadClass("org.codehaus.groovy.scriptom.ActiveXObject").newInstance("WScript.Shell")
Then you do not need to use the import statement.
Here is the thread on the mailing list
No, conditional imports are not supported... Best I can think of atm would be to use reflection as you would need to in java...
An ast transform could also be used here to tag the class and wrap the code that uses the missing class with the required reflection code
I guess a class loader could do the trick, but will be complicated.
Have you considered to use a shadow class and jsut deploy different jars?
Something like
//jdk 1.5
somethingelse extends this {
}
.
//jdk 1.6
somtheingelse extends that {
}
=> compile both to two different jar files, which you deploy on one system but not the other...
not perfect, but could work
...wait: if your libraries just differ in the package name, then you don't need a shadow class. Can't you move the one or the other in the same package?
GWT.create() is the reflection equivalent in GWT,
But it take only class literals, not fully qualified String for the Class name.
How do i dynamically create classes with Strings using GWT.create()?
Its not possible according to many GWT forum posts but how is it being done in frameworks like Rocket-GWT (http://code.google.com/p/rocket-gwt/wiki/Ioc) and Gwittir (http://code.google.com/p/gwittir/wiki/Introspection)
It is possible, albeit tricky. Here are the gory details:
If you only think as GWT as a straight Java to JS, it would not work. However, if you consider Generators - Special classes with your GWT compiler Compiles and Executes during compilation, it is possible. Thus, you can generate java source while even compiling.
I had this need today - Our system deals with Dynamic resources off a Service, ending into a String and a need for a class. Here is the solutuion I've came up with - btw, it works under hosted, IE and Firefox.
Create a GWT Module declaring:
A source path
A Generator (which should be kept OUTSIDE the package of the GWT Module source path)
An interface replacement (it will inject the Generated class instead of the interface)
Inside that package, create a Marker interface (i call that Constructable). The Generator will lookup for that Marker
Create a base abstract class to hold that factory. I do this in order to ease on the generated source code
Declare that module inheriting on your Application.gwt.xml
Some notes:
Key to understanding is around the concept of generators;
In order to ease, the Abstract base class came in handy.
Also, understand that there is name mandling into the generated .js source and even the generated Java source
Remember the Generator outputs java files
GWT.create needs some reference to the .class file. Your generator output might do that, as long as it is referenced somehow from your application (check Application.gwt.xml inherits your module, which also replaces an interface with the generator your Application.gwt.xml declares)
Wrap the GWT.create call inside a factory method/singleton, and also under GWT.isClient()
It is a very good idea to also wrap your code-class-loading-calls around a GWT.runAsync, as it might need to trigger a module load. This is VERY important.
I hope to post the source code soon. Cross your fingers. :)
Brian,
The problem is GWT.create doen't know how to pick up the right implementation for your abstract class
I had the similar problem with the new GWT MVP coding style
( see GWT MVP documentation )
When I called:
ClientFactory clientFactory = GWT.create(ClientFactory.class);
I was getting the same error:
Deferred binding result type 'com.test.mywebapp.client.ClientFactory' should not be abstract
All I had to do was to go add the following lines to my MyWebapp.gwt.xml file:
<!-- Use ClientFactoryImpl by default -->
<replace-with class="com.test.mywebapp.client.ClientFactoryImpl">
<when-type-is class="com.test.mywebapp.client.ClientFactory"/>
</replace-with>
Then it works like a charm
I ran into this today and figured out a solution. The questioner is essentially wanting to write a method such as:
public <T extends MyInterface> T create(Class<T> clz) {
return (T)GWT.create(clz);
}
Here MyInterface is simply a marker interface to define the range of classes I want to be able to dynamically generate. If you try to code the above, you will get an error. The trick is to define an "instantiator" such as:
public interface Instantiator {
public <T extends MyInterface> T create(Class<T> clz);
}
Now define a GWT deferred binding generator that returns an instance of the above. In the generator, query the TypeOracle to get all types of MyInterface and generate implementations for them just as you would for any other type:
e.g:
public class InstantiatorGenerator extends Generator {
public String generate(...) {
TypeOracle typeOracle = context.getTypeOracle();
JClassType myTYpe= typeOracle.findType(MyInterface.class.getName());
JClassType[] types = typeOracle.getTypes();
List<JClassType> myInterfaceTypes = Collections.createArrayList();
// Collect all my interface types.
for (JClassType type : types) {
if (type.isInterface() != null && type.isAssignableTo(myType)
&& type.equals(myType) == false) {
myInterfaceTypes.add(type);
}
for (JClassType nestedType : type.getNestedTypes()) {
if (nestedType.isInterface() != null && nestedType.isAssignableTo(myType)
&& nestedType.equals(myTYpe) == false) {
myInterfaceTypes.add(nestedType);
}
}
}
for (JClassType jClassType : myInterfaceTypes) {
MyInterfaceGenerator generator = new MyInterfaceGenerator();
generator.generate(logger, context, jClassType.getQualifiedSourceName());
}
}
// Other instantiator generation code for if () else if () .. constructs as
// explained below.
}
The MyIntefaceGenerator class is just like any other deferred binding generator. Except you call it directly within the above generator instead of via GWT.create. Once the generation of all known sub-types of MyInterface is done (when generating sub-types of MyInterface in the generator, make sure to make the classname have a unique pattern, such as MyInterface.class.getName() + "_MySpecialImpl"), simply create the Instantiator by again iterating through all known subtypes of MyInterface and creating a bunch of
if (clz.getName().equals(MySpecialDerivativeOfMyInterface)) { return (T) new MySpecialDerivativeOfMyInterface_MySpecialImpl();}
style of code. Lastly throw an exception so you can return a value in all cases.
Now where you'd call GWT.create(clz); instead do the following:
private static final Instantiator instantiator = GWT.create(Instantiator.class);
...
return instantiator.create(clz);
Also note that in your GWT module xml, you'll only define a generator for Instantiator, not for MyInterface generators:
<generate-with class="package.rebind.InstantiatorGenerator">
<when-type-assignable class="package.impl.Instantiator" />
</generate-with>
Bingo!
What exactly is the question - i am guessing you wish to pass parameters in addition to the class literal to a generator.
As you probably already know the class literal passed to GWT.create() is mostly a selector so that GWT can pick and execute a generator which in the end spits out a class. The easist way to pass a parameter to the generator is to use annotations in an interface and pass the interface.class to GWT.create(). Note of course the interface/class must extend the class literal passed into GWT.create().
class Selector{
}
#Annotation("string parameter...")
class WithParameter extends Selector{}
Selector instance = GWT.create( WithParameter.class )
Everything is possible..although may be difficult or even useless. As Jan has mentioned you should use a generator to do that. Basically you can create your interface the generator code which takes that interface and compile at creation time and gives you back the instance. An example could be:
//A marker interface
public interface Instantiable {
}
//What you will put in GWT.create
public interface ReflectionService {
public Instantiable newInstance(String className);
}
//gwt.xml, basically when GWT.create finds reflectionservice, use reflection generator
<generate-with class="...ReflectionGenerator" >
<when-type-assignable class="...ReflectionService" />
</generate-with>
//In not a client package
public class ReflectionGenerator extends Generator{
...
}
//A class you may instantiate
public class foo implements Instantiable{
}
//And in this way
ReflectionService service = GWT.create(ReflectionService.class);
service.newInstance("foo");
All you need to know is how to do the generator. I may tell you that at the end what you do in the generator is to create Java code in this fashion:
if ("clase1".equals(className)) return new clase1();
else if ("clase2".equals(className)) return new clase2();
...
At the final I thought, common I can do that by hand in a kind of InstanceFactory...
Best Regards
I was able to do what I think you're trying to do which is load a class and bind it to an event dynamically; I used a Generator to dynamically link the class to the event. I don't recommend it but here's an example if it helps:
http://francisshanahan.com/index.php/2010/a-simple-gwt-generator-example/
Not having looked through the code of rocket/gwittir (which you ought to do if you want to find out how they did it, it is opensource after all), i can only guess that they employ deferred binding in such a way that during compile time, they work out all calls to reflection, and statically generate all the code required to implement those call. So during run-time, you cant do different ones.
What you're trying to do is not possible in GWT.
While GWT does a good job of emulating Java at compile time the runtime is of course completely different. Most reflection is unsupported and it is not possible to generate or dynamically load classes at runtime.
I had a brief look into code for Gwittir and I think they are doing their "reflection stuff" at compile time. Here: http://code.google.com/p/gwittir/source/browse/trunk/gwittir-core/src/main/java/com/totsp/gwittir/rebind/beans/IntrospectorGenerator.java
You might be able to avoid the whole issue by doing it on the server side. Say with a service
witch takes String and returns some sort of a serializable super type.
On the server side you can do
return (MySerializableType)Class.forName("className").newInstance();
Depending on your circumstances it might not be a big performance bottleneck.