PRE-PROPOSAL: Named method parameters with defaults. (original) (raw)

Reinier Zwitserloot reinier at zwitserloot.com
Sun Mar 22 16:48:46 PDT 2009

  1. [problems with determining correct method signature] Not a (new)
    problem - that's a problem of overloading in general. Names help, if
    anything. Also one of the reasons for my suggestion to only allow
    'named' on one method in a stack of overloads. Also: that's why the
    'named' keyword is required and why there is no default 'everything is
    named' option. Old code uses no names -> no defaults either -> no
    issues with existing code that has much overloading with ample
    opportunity for ambiguous invocations if defaults are introduced.

  2. [What happens if defaults change?] Changing default value is fine
    of course - they are stored in fields in the same class as the method.

  3. [Builder pattern still needed because of order] But you CAN change
    the order.

--Reinier Zwitserloot

On Mar 23, 2009, at 00:36, Marek Kozieł wrote:

1. Problems: - in notation suggested by you, compilator and people may find problem with determining valid method signature (when we have few methods with same names) Same as now time: void a(Boo boo); void a(String booName); call: .a((String) null); now imagine that Boo is generic ...

- when some one would change default value (how already compiled code should react?), that why i think that values should be stored on special static fields. 2. Some solution could bring keeping parameter blank for default value: foo(,"bar"); // first is default; foo("bar",); // second is default; 3. Genesis If you think that this can replace builders, then in my opinion you are wrong. When class need so many parameters, so it become problem to list them in proper order, then obtaining those data is also problem, so even if we will have named parameters 'generally' problem will do not decrease. I found it while I created some library: It become common for peoples that while it was hard for them to collect all data at once they produces their own builders, so at end, to many parameters mean that in each dependent project someone will create it's own builder, and it's no mater, if they will be able to call parameters by names, or not. -- Pozdrowionka. / Regards. Lasu aka Marek Kozieł http://lasu2string.blogspot.com/

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