PROPOSAL: Auto-assignment Parameters (original) (raw)

Stephen Colebourne scolebourne at joda.org
Wed Mar 25 16:07:21 PDT 2009

Mark Mahieu wrote:

class Proposal { private final String name; private final String author; private boolean suitableForCoin; private Integer score; public Proposal(String this.name, String this.author, boolean this.suitableForCoin, int this.score) { if (name.equals(“Auto-assignment Parameters”)) { suitableForCoin = true; // final so compile-time error } } }

Very cool. I like it.

DESIGN ALTERNATIVES:

The following variations have been explored and are worth mentioning: * Allow auto-assignment parameters on all non-abstract methods. This may be especially useful on the extremely common 'setter' methods in 'value object' classes.

I think its right to leave this out for now, pending more investigation into a bigger properties solution.

* Remove the requirement for (or even disallow) the type to be specified on auto-assignment parameters. Experimentation with this idea suggests that it may work quite well for constructors, further emphasising the difference in intent and semantics from those of normal parameters. However, it may not work so well in combination with auto-assignment parameters on all non-abstract methods, and requires a change to the order in which javac compiles classes (can still pass jtreg tests).

The inference can be added later. It doesn't feel quite right.

* Allow an alternative name to be specified. This adds additional complexity to support a fractional percentage of cases, which could continue to use the existing coding pattern.

Not worth it.

Stephen

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