[Pharo-dev] Having comments for pragma?

Jan Vrany jan.vrany at fit.cvut.cz
Sat Jun 25 05:52:12 EDT 2016


> 
> In Java you *cannot* annotate any language element. You can annotate 
> class, methods, instance variables, method arguments and temporaries 
> and packages.

> Then when I take an annotation, for example an hibernate annotation:
> @Entity
> @Table(name = "EMPLOYEE")
> In the case of Hibernate, these annotation are for a class and they 
> are used at *runtime* to bind the class instances with database 
> entries (elements of this class are stored in the table EMPLOYEE).
> 
> Now I've never seen anyone doing that, but as you can access the 
> annotation at runtime, and you can extract from the annotation its 
> name and its parameters (for example you could extract "Table" and 
> "name -> EMPLOYEE". Then, using the Java reflective features, you can 
> do something like:
> 
> method = obj.getClass().getMethod(methodName, param1.class, 
> param2.class, ..);
> method.invoke(obj, arg1, arg2,...);
> And this way you execute a method named "Table", "name" or "EMPLOYEE" 
> with the parameter you want, as you could execute a method from any 
> string matching a method name. We have the same primitive in Pharo on 
> CompiledMethod.
> 
> 
> I would not say that pragmas are more powerful in Java. Can you give 
> an example of something you can do with the Java annotation that you 
> can't do with Pharo pragmas ?

Out of a curiosity,  how can I annotate class, instance variable, 
method argument or temporary, or package.
How can I annotate the pragma definition itself? How can I retrieve 
annotations of a pragma definition?

I mean, I understand that you can *achieve* same effect, but you *can* 
achieve it as well with no pragma support at all.

Jan

> In Slang we use pragma to annotate argument and temporary variables 
> and it works just fine. When you describe in Pharo classes and 
> instance variables using Magritte you can do the same thing as just 
> annotating them.
> 
> 
> 
>> Stef
>> 
> 
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