NSPredicate : CoreData fetchRequest filtered by Array of dictionaries

问题

Is it possible to create an NSPredicate using an array of dictionaries ?

I have a following structure :

[{ name: "foo", city:"Paris"},{name:"bar", city:"London"}]

An I want to filter my NSFetchRequest by these pairs. (supposing the properties have the same names in CoreData)

When passing an array I can use the keyword IN. But I don't get how make this work with an array of dictionaries.

回答1:

I don't think you will be able to use IN, so you need to use a number of ORs. In outline:

1. Iterate through all elements of the array.

2. For each element (dictionary), construct a predicate of the form:

   [NSPredicate predicateWithFormat:@"name == %@ AND city == %@",[dictionary objectForKey:@"name"], [dictionary objectForKey:@"city"]];
   

3. Add each such predicate to a NSMutableArray (array) of predicates

4. Build a compound predicate from the array using:

   [NSCompoundPredicate orPredicateWithSubpredicates:array]
   

If performance is an issue, consider building the individual predicates with substitution variables rather than with format.

来源：https://stackoverflow.com/questions/29836516/nspredicate-coredata-fetchrequest-filtered-by-array-of-dictionaries