the advantage to subclassing is that you're working better with the type
system whereas static pulls you out of the object world and should be used
with great caution. for example, subclassing enables more subclassing and
therefore more reusability. static factory methods cannot be specialized. i
also feel it's more intuitive to users for something like this. if you want
to see all the textfields on your project and you subclass textfield, you
can bring up textfield and hit F4 in eclipse and see the class hierarchy.
static factory methods are a bit more hidden to quick inspection. i like
static factory methods for things like units (Distance.meters(...) versus
Distance.feet(...)) or if you want to vary the subclass returned.
one improvement i'd make:
public class EmailField extends TextField
and write an EmailConverter. another reason subclassing is best.
Christian Helmbold-2 wrote:
>
>
> I think the difference between sub classing and static factory methods is
> a matter of taste in this case.
>
> If I have many fields, I'd need many classes for them. So I'd group them
> in a sub package. In the case of factory methods I'd group the methods to
> create fields in a class instead of a package.
>
> Subclass:
>
> 1 class UserEmailField extends TextField {
> 2 public UserEmailField(String id, IModel model) {
> 3 super(id, model);
> 4 setRequired(true);
> 5 add(EmailAddressValidator.getInstance())
> 6 add(UniqueValidator.unique(SystemUser.class, "email"));
> 7 }
> 8 }
>
> Factory method:
>
> 1 public static TextField emailTextField(String id){
> 2 return (TextField) new TextField(id)
> 3 .setRequired(true)
> 4 .add(EmailAddressValidator.getInstance())
> 5 .add(UniqueValidator.unique(SystemUser.class,
> "email"));
> 6 }
>
> Your answer shows me, that there is no dramatically simpler way to do
> this. If you ignore the two lines for factory class declaration factory
> methods are even a bit shorter. Or is there an advantage of sub classing
> that I have missed?
>
> Regards,
> Christian
>
>
>
> ----- Ursprüngliche Mail ----
>> Von: Igor Vaynberg <[email protected]>
>> An: [email protected]
>> Gesendet: Freitag, den 8. Mai 2009, 09:08:34 Uhr
>> Betreff: Re: How to avoid code duplication on forms?
>>
>> much simpler
>>
>> class UserEmailField extends TextField {
>> public UserEmailField(String id, IModel model) {
>> super(id, model);
>> add(EmailAddressValidator.getInstance())
>> add(UniqueValidator.unique(SystemUser.class, "email"));
>> }
>> }
>
>
>
>
>
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