NSPredicate comparing transformed CLPlacemark with another CLPlacemark

问题

I'm saving CLPlacemark in Core data using NSValueTransformer. (so it's saved as NSData)

However I've come to a point where I need to filter the saved objects based on another CLPlacemark object.

I've tried this, it doesn't work:

NSExpression *exprPath = [NSExpression expressionForKeyPath:@"placemark"];
NSExpression *exprKeyword = [NSExpression expressionForConstantValue:[NSKeyedArchiver archivedDataWithRootObject:placemark]];
NSPredicate *predicate = [NSComparisonPredicate predicateWithLeftExpression:exprPath rightExpression:exprKeyword modifier:NSDirectPredicateModifier type:NSEqualToPredicateOperatorType options:0];

So any other suggestions?

回答1:

Core Data supports == and != searches against binary data (and transformable attributes). Do not use NSKeyedArchiver for your placemark. Just use it as is in predicate like this:

[NSPredicate predicateWithFormat:@"placemark = %@", placemark]

来源：https://stackoverflow.com/questions/15204498/nspredicate-comparing-transformed-clplacemark-with-another-clplacemark