ios Coredata relationship query - ios

Question

I have a question regarding the core data relationship. I have to create a core data for following features of device catalog:
where device contains device name, device SKU number, device price, device brand and color. I have a filter in my application which queries all data based on the respected filter. like if the user clicks brand, it will show a list of brands and then filter apply on a dataset for particular brand only, same for color if the user chooses any color it will show devices with a particular color. also, the user can select multiple filters also like brand + color.
under this situation I created this data model :
here I created 3 different tables where device have many to many relationships with color, as the device can have multiple colors. and colors can have multiple devices.
for the brand, I use many to one relationship. as one device can have only one brand but on the other hand, a brand can contain multiple devices.
forgetting all devices I write this code :
-(void)loadAllDevices{
// Fetching
NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] initWithEntityName:#"Device"];
// Add Sort Descriptor
NSSortDescriptor *sortDescriptor1 = [NSSortDescriptor sortDescriptorWithKey:#"deviceName" ascending:YES];
NSSortDescriptor *sortDescriptor2 = [NSSortDescriptor sortDescriptorWithKey:#"devicePrice" ascending:YES];
[fetchRequest setSortDescriptors:#[sortDescriptor1, sortDescriptor2]];
// Execute Fetch Request
NSError *fetchError = nil;
NSArray *result = [self.managedObjectContext executeFetchRequest:fetchRequest error:&fetchError];
if (!fetchError) {
for (NSManagedObject *managedObject in result) {
NSLog(#"DeviceName = %#, DevicePrice = %#", [managedObject valueForKey:#"deviceName"], [managedObject valueForKey:#"devicePrice"]);
Brand * deviceBrand = [managedObject valueForKey:#"deviceBrand"];
NSLog(#"Device Brand = %#",deviceBrand.brandName);
NSSet *deviceColorSet = [managedObject valueForKey:#"deviceColor"];
for (Color *color in deviceColorSet) {
NSLog(#"Device Color = %#", color.colorName);
}
}
} else {
NSLog(#"Error fetching data.");
NSLog(#"%#, %#", fetchError, fetchError.localizedDescription);
}
}
but now I want to add a filter based on the condition I describe above, how can I write predicates based on this. any help or a direction to this will be appreciated.
**
UPDATE:
As describe in comments if i'm using predicate like this :
NSPredicate *predicate = [NSPredicate predicateWithFormat:#"deviceBrand.brandName CONTAINS[cd] %#", #"Apple"]; [fetchRequest setPredicate:predicate]; and NSPredicate *predicate = [NSPredicate predicateWithFormat:#"deviceColor.colorName CONTAINS[cd] %#", #"Blue"]; [fetchRequest setPredicate:predicate];
separately it given me correct result.
but if i try to combine both its not providing me any result. i try this predicate:
NSPredicate *predicate = [NSPredicate predicateWithFormat:#"deviceBrand.brandName == %# AND ANY deviceColor.colorName == %#", #"Apple", #"Blue"];
any idea whats i'm doing wrong here.
**

Answer 1

Suppose you have two variables, selectedBrand and selectedColor which are the brand and color details you want to match. Then your predicate would look like this:
fetchRequest.predicate = [NSPredicate predicateWithFormat:#“deviceBrand.brandName == %# AND ANY deviceColor.colorName == %#“, selectedBrand, selectedColor];
This assumes you want to want to return results where both brand and color match - if you want results where either matches, change AND to OR.

Answer 2

If the only property of your color and brand models are their name and the only usage of these datas are for filtering and search, modeling your data in such situation has a low performance. So its better you add just brandName instead of brand model and colorName instead of color model, and filter your devices based on them.
Even if you want infos more than name into brand and color, its better to save the brandName and colorName in device model separately, to have an efficient filtering and searching results and then use the brand model only when you want to show more info about a particular brand to user.