RE: pvData change suggestion

[<jam...@di...>]

Hi Matej

Just got to this, looks fine for a quick fix. Eliminates the two names given to structureArrays.

James


> -----Original Message-----
> From: Matej Sekoranja [mailto:mat...@co...]
> Sent: 24 January 2012 23:38
> To: epi...@li...
> Subject: pvData change suggestion
> 
> Hi,
> 
> on the train I have some time to think... here is what I've come up with.
> Changes are minor.
> 
> If we simply add a method createStructure(Field[]) that creates so called
> "anonymous structure", we can get something that produces the "result" we
> want:
> 
> 
> Scalar xField = fieldCreate.createScalar("x", ScalarType.pvDouble); Scalar
> yField = fieldCreate.createScalar("y", ScalarType.pvDouble); // this is a new
> method, it creates an anonymous structure Structure pointStructure =
> fieldCreate.createStructure(new Field[] { xField, yField } );
> 
> // note that pointStructure has no name, so we do not have a problem with 2
> names...
> StructureArray points = fieldCreate.createStructureArray("points",
> pointStructure);
> 
> 
> Scalar valueField = fieldCreate.createScalar("value", ScalarType.pvInt);
> 
> // in order to add name to a structure you must wrap it with the
> StructureMember class Structure topStructure = fieldCreate.createStructure(
>     new Field[] {
>         valueField,
>         points,
>         new StructureMember("point1", pointStructure),
>         new StructureMember("point2", pointStructure)
>     });
> 
> 
> ---
> 
> Now, how to "tweak" current code that is still works.
> Currently Field interface declares getFieldName(). Structure extends Field.
> Note that javaIOC XML parser uses getFieldName() for different reasons that as
> a member name.
> 
> Implementation of a new method createStructure(Fields[] fields) becomes:
> 
> public Structure createStructure(Field[] field) {
>     return new BaseStructure(null,field); }
> 
> We declare StructureMember as:
> 
> final class StructureMember implements Structure {
>     private final Structure structure;
>     private final String memberName;
> 
>     public StructureMember(String memberName, Structure structure)
>     {
>         this.memberName = memberName;
>         this.structure = structure;
>     }
> 
>     // we implement getFieldName() to return memberName instead of null
>     // getFieldName() should be called getMemberName(), but its called
> getFieldName() due to legacy code
>     public String getFieldName()
>     {
>         return memberName;
>     }
> 
>     public Type getType()
>     {
>         return Type.pvStructure;
>     }
> 
>     // for rest of Structure implementation we simply delegate a call to
> structure instance.
> }
> 
> pvAccess code is changed: Structure/StructureArray serialization, caching,
> etc...
> 
> 
> We deprecate method fieldCreate.createStructure(String fieldName, Field[]
> fields) - should not be used, since it does not allow sharing of introspection
> instances. However when sent over the wire, sharing will happen.
> 
> getFieldName() is used as "member name". Since scalars, arrays and
> structureArrays are never standalone current methods are OK.
> The only "problem" are structure. For this we use StructureMember.
> Note that we can use getFieldName() for top structure or not.
> 
> Matej
> 
> ps I wrote this pretty fast... so I hope it is understandable.
> 
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