Re: RPGle - i wish i could do some 'Reflection'

Most other languages use the equivalent of data structures for objects as well, under the covers at least.

When you instantiate an instance of an object, you are really running code that builds the in-memory structures.

Much the way you can retrieve information about a table or record from the sys* tables in DB2, except it makes a unique copy of the object.

Building reflection into RPG would have some pleasant results, but if you really need it, the capabilities to do it are there. Start with the process you would need to instantiate a new object.

Paul


Typos courtesy of my iPhone and my fat fingers!

On Oct 30, 2013, at 9:28 AM, whatt sson <whattssonn@xxxxxxxxx> wrote:

A better thing to wish for is built-in suppport for maps/dictionaries (e.g.
the "Map" class in Java).

Add/remove/sort keys and values in a map, easily.
Then you would also have "reflection", or simply you can query the keys,
etc.

Btw, a map's value could be another map.

Data structures are - be definition - static structures layed out in memory
without any meta data (like the names of the fields etc).
This is by design, it makes them efficient.

What you really want is support for MAPS.




On Wed, Oct 30, 2013 at 3:21 PM, Charles MARTIN <cmartin@xxxxxxxxxxxxxxx>wrote:

Hello everyone,

I wish i could do some reflection using RPGLe.
By reflection, I mean :
'The process or mechanism of determining the capabilities of an object at
run-time.'

Imagine you have this datastructure :

D DS_Format DS Qualified Based(pDS_Format)
D Type 20I 0 Inz(1)
D Label 50A Inz('myLabel')
D Description 5000A Inz('myDescription')

With a reflection api, I could do this :
Reflection_ListSubfields(DS_Format);
=> return this array : { 'Type', 'Label', 'Description' }
And then, I could do :
Reflection_GetSubfield(DS_Format : 'Label');
=> return 'myLabel'

I wish i could do this too :
Reflection_GetSubfieldType(DS_Format : 'Label');
=> return 'A'
Reflection_GetSubfieldLength(DS_Format : 'Label');
=> return 50
Reflection_GetSubfieldPrecision(DS_Format : 'Type');
=> return 0


With this, I expect I could do something like this (with some little work)
:
SerializeXml(DS_Format); //I build xml with one line of code !
And get :
<DS_Format>
<Type>1</Type>
<Label>myLabel</Label>
<Description>myDescription</Description>
</DS_Format>
And conversely with DeserializeXml(myXml);

Reflection would help me to build really cool apis.
Is there any way ?

Charles
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