Nspredicate with Swift and Core Data

NSPredicate with Swift and Core Data

If formUUID is an NSString or a Swift String then you have to use the
%@ placeholder:

let resultPredicate2 = NSPredicate(format: "formUUID = %@", formUUID)

Filter Vs NSPredicate in coredata

From Persistent Store Types and Behaviors in the Core Data Programming Guide (emphasis added):

Fetching differs somewhat according to the type of store. In the XML, binary, and in-memory stores, evaluation of the predicate and sort descriptors is performed in Objective-C with access to all Cocoa functionality, including the comparison methods on NSString.

The SQLite store, on the other hand, compiles the predicate and sort descriptors to SQL and evaluates the result in the database itself. This is done primarily for performance, ...

You can verify that by enabling Core Data debugging. Set

-com.apple.CoreData.SQLDebug 3
-com.apple.CoreData.Logging.stderr 1  

as environment variables and you'll see the SQLite statements as they are executed.

core data how to filter (NSPredicate) including a relationship requirement and given the relationship object?

The predicate would be what you expect.

NSPredicate(format: "name = %@ && school = %@", "Tom", school)

However, you can get to the person without a predicate by using the relationship in the other direction and filter.

let tom = school.persons.filter { $0.name == "Tom" }.first

(You might have to cast your NSSet to Set<Person>).

Can I use an NSPredicate in Swift with a nil argument?

It looks as if it is (with the current Xcode 6 beta 3 release) generally difficult
to pass nil in a variable argument list.

This seems to work:

let predicate = NSPredicate(format: "parentFolder == %@", 0)
print(predicate)
// Output: parentFolder == nil

But the easiest solution would be to simply write the predicate as

NSPredicate(format: "parentFolder == nil")

Swift Core Data Predicate IN Clause

You don't show how you are defining recentEmployeeIds, but assuming its something like

let recentEmployeeIds:[Int] = ...

then you need to init the NSPredicate correctly. There is no label for argumentArray

fetchRequest.predicate = NSPredicate(format: "ANY id IN %@", recentEmployeeIds)

Core Data NSPredicate - Match Dates

First of all the exception occurs because the placeholder %@ is wrong. %@ is for objects, a Double value is represented by %f.

Second of all if you want to fetch all dates which are in a specific day you have to create a date range (0:00–23:59) of that day.

Using Calendar you get 0:00 with startOfDay(for:) and the end of the day by adding a day and the < operator.

For example

let calendar = Calendar.current
let startDate = calendar.startOfDay(for: selectedDate)
let endDate = calendar.date(byAdding: .day, value: 1, to: startDate)!
let predicate = NSPredicate(format: "date >= %@ AND date < %@", argumentArray: [startDate, endDate]))

Swift 5 CoreData predicate using UUID

• The %K format expects a key path string, this can be obtained using the #keyPath directive.
• The %@ format expects an Objective-C object, here we can use the toll-free bridging between UUID and NSUUID.

That gives:

let predicate = NSPredicate(format: "%K == %@",
                            #keyPath(Bike.bleID), bleID as NSUUID)

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