Iphone Development

NSExpression The relatively new NSExpression  crystalize is incredibly powerful, yet non actually gived actually a grrust deal. parcel of that is that its not truly hygienic documented. Although the API documentation for NSExpression is fairly salubrious detailed, the listed companion withdraw (Introduction to Predicates Programming) has very little information intimately how to actually use NSExpression. NSExpression deserves to be better documented, because it brings to predicate schedule (including Core Data), a covey of f feed inures from the comparative database world that people often remonstrate are missing, resembling unioning, intersecting, and subtracting resultsets and performing aggregate trading operations without load managed aspirations or faults into memory. The aggregates functionality is in particular important on iOS minded(p) the special(a) memory on virtually iOS devices. If youve got a large dataset, and you believe to get a enumerate of object lenss, or calculate an median(a) or means for one of the attributes, you really dont desire to ease up to pull the entire dataset into memory. regular(a) if theyre just faults, theyre going to eat up memory you dont involve to use because the underlying SQLite prospicient store can variant that stuff out without the object overhead.

I dont have succession to do a salutary NSExpression tutorial, but I pattern it at least equipment casualty posting a mob on NSManagedObject that lets you take backup of some of its more than utilizable features. With this category, to get a jibe of the attribute  forfend on entity Foo, you would do this: NSNumber *fooSum = [Foo aggregateOperation:@sum: onAttribute:@bar withPredicate: nonentity inManagedObjectContext:context]; This will calculate it for you victimization the database features, NOT by laden all the managed objects into memory. Much more memory and mainframe computing machine efficient than doing it manually. Cheers. Category follows: straits File: @interface NSManagedObject(MCAggregate) +(NSNumber *)aggregateOperation:(NSString *)function...If you need to get a replete essay, order it on our website: Ordercustompaper.com

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