Re: Chained call pattern with inheritance, polymorphism and generics...

 Daniel Pitts <>
Sat, 29 Sep 2007 19:02:23 -0000
On Sep 28, 11:57 pm, Piotr Kobzda <> wrote:

Daniel Pitts wrote:

What's wrong then with pattern presented by Daniel to achieve that?

I can't make any sense of it.

What if I changed it to this:

public class BaseBuilder<T> {
    private String something;
    public T something(String something) {
       this.something = something;
       return getChainTarget();

I guess, it should return getChainLink() here.


    protected abstract T getChainLink();

public class SpecificBuilder extends BaseBuilder<SpecificBuilder> {

    private String other;

    public SpecificBuilder other(String other) {
        this.other = other;

    protected SpecificBuilder getChainLink() {
     return this;

SpecificBuilder b = new

This works since something() returns T, which in SpecificBuilder IS

The problem with my solution is that I can't have:

Of course you can:

class MoreSpecificBuilder extends SpecificBuilder {
    public void doMore() {
    protected MoreSpecificBuilder getChainLink() {
     return this;

      public MoreSpecificBuilder something(String something) {
          return getChainTarget();

      public MoreSpecificBuilder other(String other) {
          return getChainLink();


new MoreSpecificBuilder().something("hello").doMore(); // whoops!

Try it now! :-)


The point is, I shouldn't have to delegate to super just to return the
same reference as a different type.

While that IS currently the case, I wish it werent.

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