CoreData exception/crash using NSInMemoryStoreType and NSExpressionDescription

Number:rdar://12021880 Date Originated:8/2/2012
Status:Open Resolved:
Product:iPhone SDK Product Version:5.1
Classification:Bug Reproducible:Always

I have a simple CoreData-backed iOS project, with a test suite using an NSInMemoryStoreType data store.  When I perform a fetch request which uses an NSExpressionDescription (to calculate an average for a field) I get a crash with -[__NSCFNumber count]: unrecognized selector sent to instance.  When I switch the store type to NSSQLiteStoreType the fetch succeeds as expected.

Steps to Reproduce:

given an otherwise working NSFetchRequest, configure with the following code:

        [fetchRequest setResultType:NSDictionaryResultType];

        NSExpression *keyPathExpression = [NSExpression expressionForKeyPath:@"duration"];
        NSExpression *avgExpression = [NSExpression expressionForFunction:@"average:" arguments:[NSArray arrayWithObject:keyPathExpression]];

        NSExpressionDescription *expressionDescription = [[NSExpressionDescription alloc] init];
        [expressionDescription setName:@"averageDuration"];
        [expressionDescription setExpression:avgExpression];
        [expressionDescription setExpressionResultType:NSDoubleAttributeType];

        [fetchRequest setPropertiesToFetch:[NSArray arrayWithObject:expressionDescription]];

NSArray *resultSet = [context executeFetchRequest:fetchRequest error:&error];

Expected Results:

Executing the fetch request should succeed and return a dictionary in the resultSet array, with an NSNumber for the averageDuration key

Actual Results:

An exception/crash with -[__NSCFNumber count]: unrecognized selector sent to instance. Switching to an NSSQLiteStoreType results in the request succeeding as expected.


2 years later - not fixed

Posted my as: rdar://16644607

By jkirsakmens at April 17, 2014, 9:05 a.m. (reply...)

Had the same issue - thanks for pointing out that is it linked to the use of NSInMemoryStoreType.

I posted a duplicate bug report (rdar://12795203).

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