Databases
StackOverflow2013
Postsdbo
POFactory pattern
 

Note that there are some explanatory texts on larger screens.

plurals
  1. POFactory pattern
    primarykey
    data
    text
    <p>I've been trying to create a factory (in Java) that prohibits subclassing of the factory product and prevents the concrete factories from being used by anyone except the abstract factory. What do you think of this...</p> <pre><code>class Client { public static void main(String[] args) { Animal animal = Animal.create(Lion.class); animal.doGrowl(); animal = Animal.create(Cow.class); animal.doGrowl(); } } final class Animal { private Growl growl = null; private Animal() { } public void doGrowl() { growl.exec(); } public abstract class Growl { public abstract void exec(); public final void initialize() { if (growl != null) { throw new IllegalStateException("Already initialized."); } growl = this; } } public abstract static class Factory { public Factory(FactoryInitializer initializer) { initializer.validate(); } public abstract void attachGrowl(Animal a); } public static final class FactoryInitializer { private boolean isValid = true; private FactoryInitializer() { } public void validate() { if (isValid) { isValid = false; } else { throw new IllegalStateException("FactoryInitializer is not valid."); } } } public static Animal create(Class&lt;? extends Factory&gt; factoryClass) { try { Constructor constructor = factoryClass.getConstructor(new Class[]{FactoryInitializer.class}); Factory factory = (Factory) constructor .newInstance(new Object[]{new FactoryInitializer()}); Animal animal = new Animal(); factory.attachGrowl(animal); if (animal.growl == null) { throw new IllegalStateException("Animal factory did not initialize Growl."); } return animal; } catch (Exception e) { return null; } } } class Lion extends Animal.Factory { public Lion(Animal.FactoryInitializer initializer) { super(initializer); } public void attachGrowl(Animal a) { a.new Growl() { public void exec() { System.out.println("rarrrrrr"); } }.initialize(); } } class Cow extends Animal.Factory { public Cow(Animal.FactoryInitializer initializer) { super(initializer); } public void attachGrowl(Animal a) { a.new Growl() { public void exec() { System.out.println("mmooooo"); } }.initialize(); } } </code></pre>
    singulars
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. PTQuestion
    1. USTofuBeer
    1. USDW.
    plurals
    1. This table or related slice is empty.
    1. PL
      singulars
      1. LTLinked
    1. This table or related slice is empty.
    1. PO
      singulars
      1. PTAnswer
    2. PO
      singulars
      1. PTAnswer
    3. PO
      singulars
      1. PTAnswer
    1. VO
      singulars
      1. POFactory pattern
      1. This table or related slice is empty.
      1. VTUpMod
    2. VO
      singulars
      1. POFactory pattern
      1. This table or related slice is empty.
      1. VTDownMod
    3. VO
      singulars
      1. POFactory pattern
      1. This table or related slice is empty.
      1. VTDownMod
    1. COCan you give an English description of a real world problem that this would address?
      singulars
      1. POFactory pattern
      1. USTofuBeer
    2. COI asked this a while ago and never really explained why I wanted to know this. Basically I was creating a modular music synethsizer (like Music N) and wanted api users to be able to implement their own unit generators, which are basically objects that synthesize or process signal (float array) and can be connected together. I guess I was just peeved no one saw value for this on its own.
      singulars
      1. POFactory pattern
      1. USDW.
    3. COIf I recall correctly I wanted to prohibit subclassing because I wanted to encourage api users to break things into re-usable, connectable pieces (not one giant subclass of a subclass of a...) and I wanted to force them to implement the abstract method--the one that processes the input signal and outputs result.
      singulars
      1. POFactory pattern
      1. USDW.
 

Querying!

 
Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload