I have an Employee entity which inherits from a Human entity. I cannot access or set the inherited attribute (property) name on my Employee instance in code using dot syntax, however using setValue(forKey) works.
I have included 2 screen shots:
The Human entity is abstract, however even if I don't put abstract it still does not let me access the inherited attributes via dot syntax. I also tried changing the Codegen to Class Definition and still doesn't work. Am I doing something wrong or is this the standard way of accessing inherited attributes. Any solution to this problem is helpful.
Related
I have problems to check if a persistent property in grails has an specific annotation for fields that belong to superclass ... ane then get it's name and value.
I am getting the persistence properties as:
GrailsDomainClassProperty[] persistentProperties = new DefaultGrailsDomainClass(entityClass).getPersistentProperties();
That works great ... but later i found that getDeclaredFields only retrieves the actual class fields (not superclass) and things starts to look not very Groovy.
Is there a prefered Groovy way to do this?
No, you should use this code for all super classes. The same will be for children classes.
I need to do some custom data binding and I tried to use the #BindUsing annotation on a class (http://grails.org/doc/latest/api/org/grails/databinding/BindUsing.html), however, it's being ignored. I am under the assumption that since the annotation is used on the class that would mean that every time a data binding happens and that class is involved, the BindingHelper class would be used, but it's never actually called. Is there something that I'm missing or doing wrong?
Here's the class definition where UserBinding is a class that implements the BindingHelper interface:
#BindUsing(UserBinding)
class User extends SomeOtherClass
{
...
Also am I correct in understanding that basically creating a ValueConverter and using #BindUsing on a class accomplish the same thing?
BindUsing on a class is not used often and there seems to be a bug reported around that already. [From the link] The problem could be that there are multiple request parameters with the same name it might be using the helper only for the first one.
Using a property level #BindUsing annotation should be simpler to implement and is less likely to fail (even when there are multiple entries in the params map with the same name).
Google is useless for these sorts of searches, because you get hundreds of millions of results absolutely none of which relate to the specific question.
The question is simply this:
Is it possible to have a Class Reference Property in Delphi?
If so, how?
Here's what I've tried...
type
TMyObject = class
// ...
end;
TMyObjectClass = class of TMyObject
TMyObjectA = class(TMyObject)
// specifics here
end;
TMyObjectB =class(TMyObject)
// specifics here
end;
TMyComponent = class(TComponent)
private
FObjectType: TMyObjectClass;
published
property ObjectType: TMyObjectClass read FObjectType write FObjectType;
end;
The above code compiles fine, however the Object Inspector does not show the ObjectType property at all.
My objective here (if you haven't already guessed) is to make it so that I can select a class descendant from a specific base class, to make the same component behave in a different way.
I want to do it this way so that the component doesn't need to know about the sub-classes directly (it needs to be fully modular).
Let me just make this bit clear: I cannot use an Enum to choose between the sub-class types as the component cannot directly link to the sub-class types (It's simply not possible in this particular case)
Anyway... thanks in advance!
You can find all classes that descend from a particular base class: Delphi: At runtime find classes that descend from a given base class? and make this a special property with list of values using TPropertyEditor.
If you were going to do this then you would need to provide a property editor. The IDE does not come with property editors for class type properties. You would also need to handle .dfm persistence. You would write the class type out to the .dfm file as a string and when the .dfm file is read, you would need to fixup the reference. New style RTTI could do that.
However, I don't think any of this is actually viable for the following reason. Your design time code runs in a package inside the IDE and does not have access to the class types in the active project in the IDE. Those class types only exist when that project runs. So the ObjectType property in the code in your question cannot be assigned to anything meaningful in the design time package. Well, you could use it for classes defined in the VCL and any other packages installed in your IDE but I rather imagine you'd want to use it on classes defined in the active project.
I think all this means that you should instead use a simple string property and fixup the class type references only at runtime.
Lets say I have 2 class types TEmployee (with properties A,B) and TDept (with properties C,D). Then I make a class descended from TList like so :
TMyCcontainer<T>=class(TList<T>)
So I can create instances of TMyCcontainer and fill with TEmployee or TDept. In my TMyCcontainer class is there anyway to access properties A,B of TEmployee, or properties C,D of TDept?
Of course the type is generic so it would appear not. And this is the problem I always have with generics - maybe I am mis-using them. I recently learnt abaout constraints, and thought I had found out what I had been missing....
So I created 2 interfaces say IEmployee and IDept, made my 2 orig class es to be interfaceobjects, and put in my contraint on my Tlist ie
TMyCcontainer<T:IEmployee,IDept>=class(TList<T>)
Of course I was quickly disappointed as this is saying you must implement BOTH of these interfaces in any type I put in my generic TList (TMyContainer), whereas I just want ONE in any particular instance, then ther other in another instance. I would have to implement both IEmployee and IDept in my TDept class which is not what I want obv.
Is there any good way to access members of a Type within a generic container? Or should I not be using generics to do this type of thing. Ty
All generic constraints you put on a class have to be fulfilled by the generic type. Looks like what you're really looking for is two different generic types: TMyContainer<TDept> and TMyContainer<TEmployee>. Then you'll have access to all the properties of those types, individually.
I am trying to make a taglib to represent an object (to read and display at the UI). When creating an object (save method in the controller), I see the domain class and association are created by the auto assignment of parameter
def Book = new Book(params)
It also maps complex types (for eg: joda time). I wonder about the naming convention necessary to facilitate this mapping. Out of curiosity, can someone also point where in the grails source code I could see how grails handles this mapping. I'm still learning Spring and probably this would be a good exercise.
Thanks,
Babu.
AFAIK the naming conventions are rather straightforward. If there's a field params.foo and the object you are binding to has a field foo, it will bind the value, assuming the type conversion works properly. If there's a params.bar.id set with an Long value and your object has a complex property of type Bar, it will lookup this instance and inject it.
If you need more control over the binding process, you might want to use bindData.
If you are interested into the details of the binding process, have a look at Java's PropertyEditor as this is what is being used in the background. I wrote a blog post on how to create and register PropertyEditors a while ago, maybe it helps you getting started with that stuff.