Search code examples
ioscore-datanspredicate

CoreData NSPredicate with relationship

I have following CoreData objects Model

enter image description here

Now I am having issue in making a predicate with following conditions.

Fetch all those DBOpportunity WHERE

DBOpportunity.stateCode == 1

AND

DBOpportunity.invoiceDate >= GIVEN_DATE

AND

DBOpportunityLines.crmAccept == 1 OR DBOpportunityLines.crmAccept == 3

I have tried lots of examples and programming guide by the apple but can't able to achieve this.

Solution

  • opportunitylines is a to-many relationship, so there are multiple DBOpportunityLines objects for one DBOpportunity object. Assuming that the last condition

    DBOpportunityLines.crmAccept == 1 OR DBOpportunityLines.crmAccept == 3

    should hold for any of the related objects, you need a SUBQUERY:

    NSDate *givenDate = ...;
NSPredicate *predicate = [NSPredicate predicateWithFormat:@"stateCode == 1 AND invoiceDate >= %@ "
    "AND SUBQUERY(opportunitylines, $x, $x.crmAccept == 1 OR $x.crmAccept == 3).@count > 0",
    givenDate];

    Remark: Unfortunately, the usage of SUBQUERY in predicates is poorly documented. There is one example in the NSExpression class reference. See also Quick Explanation of SUBQUERY in NSPredicate Expression.