Item filter

[sbcgua]

Follows #71 (comment) @larshp

perhaps something like adding this method to the custom mapping interface

methods to_json_skip_value
  importing 
    io_type type ref to cl_abap_typedescr
    is_node type ty_node,
  returning 
    value(rv_skip) type abap_bool.

if it returns rv_skip = abap_true, then skip the value, else as normal

1. This seems to be not about skipping but about filtering, the implementation may decide to skip filled values too
2. Thus it doesn't match mapper semantics, it is a separate filter interface
3. Also because of performance considerations. Mapper without filter will call extra method each time and vice versa

interface zif_ajson_filter " zif_ajson_node_filter ?

  methods filter
   importing 
     io_type type ref to cl_abap_typedescr
     is_node type ty_node,
   returning 
     value(rv_KEEP) type abap_bool.

[larshp]

true,

is_node has value as a string, perhaps also pass a reference to the abap value?

[sbcgua]

NB, thoughts: typical usages to maybe implement within the package:

• filter all empty nodes
• filter out specific paths
  • maybe, makes sense to coordinate with #63 (in the long run ...)
• maybe implement filter chains (multiple filters)

[sbcgua]

push( X )
push( Y )
push( Z )

where Y is filtered, should result in [X, null, Z], isn't it ?

[sbcgua]

... just an occasional finding ... seems that unexpectedly ls-x = 123. append ls to tab is faster than append initial value to tab assigning <rec>. <rec>-x = 123. And ... 30% faster. WTF ?

UPD: Ok... a bit better with clear. But still, how come ?

[sbcgua]

@larshp have a look at #76

• Really draft at this moment
• children count fails
• merging ajson has a potential misuse
• and value is not transferred to the filter (e.g. to hide whole structure or table)
• a lot of code duplication...

By the way do you need io_type in the filter ? I guess not if value itself is passed ? It is no very clear what to pass therein some cases (see lo_null_type)

[larshp]

io_type: perhaps the value part of is_node is enough, but I'd like to be able to do "if value is initial then skip field", the to be able to determine if the value is initial, it requires the type of the node? but again, perhaps the json type(part of is_node) is enough

[sbcgua]

OK, so it is kind of ready though needs more testing and unit testing ...

    li_json_filtered = zcl_ajson=>create_from(
      ii_source_json = li_json_source
      ii_filter = zcl_ajson_filter_lib=>create_empty_filter( ) ).

also implemented "in the box" filtering by path and "and-filtering" to combine filters. See UTs of ZCL_AJSON_FILTER_LIB - https://github.com/sbcgua/ajson/pull/76/files#diff-4eed2314d42108a56f62bcc604d05b97749a05068d82d3d63800495d84fd0a16

The interface zif_ajson_filter allows creating custom filters. Note iv_visit param - objects and arrays trigger filter 2 times - on open and on close. On open children = original value, on close children = filtered value (so after filtering child nodes). Array indexes are re-numbered (so filtering 2nd item of [1,2,3] will give [1,2] )

@larshp

[sbcgua]

Also I'm a bit tentative about instantiation. create_from has filter as optional param. So also intended for copy. And copy would probably assume copying of attrs like mapper and keep_order ... and it does not because the source is the interface not the class ... so ... it might be misleading, maybe it should be just create_filtered with mandatory filyer param. Or, maybe it should be a method of ajson interface ... which makes sense ... but then interfaces will be cross dependent ...
@larshp

[sbcgua]

v1.1.1-beta published. Please mind that it has a beta status. I'm still doubtful about create_from semantics above. BTW would appreciate your opinion @larshp ( create_from vs create_filtered vs zif_ajson->filter )

[sbcgua]

Can be closed ? Seems to be implemented by now