objective c - RestKit: Composing Relationships with the Nil Key Path -

i have 2 classes

• author attributes id, papers (paper relationship), ...
• paper attributes id, mainauthor (author relationship), authors (author relationship) ...

and want map json it

"authors": [     {         "id": 123,         "papers": [             {                 "id": 1,                 "main_author_id": 123,                 ...             },             ...         ]     },     ... ] 

the problem json not structured

"authors": [     {         "id": 123,         "papers": [             {                 "id": 1,                 "main_author": {                     "id": 123                 }                 ...             },             ...         ]     },     ... ] 

so map things (note *main_author* part of both json examples). tried using mapping value without key path explained here:

[authormapping addattributemappingtokeyofrepresentationfromattribute:@"main_author_id"]; [authormapping addattributemappingsfromdictionary:@{@"(main_author_id)": @"id"}]; 

but i'm getting error telling me keypath id exists , may not add second mapping keypath. totally understand error, have no idea how map *main_author_id* id. changing data source may best solution, unfortunately not possible.

any suggestion highly welcome! thanks!

this foreign key mapping for. allows temporarily store 'identity' value you're provided , restkit find appropriate object , complete relationship.