QueryKit
QueryKit, a simple type-safe Core Data query language.
Usage
QuerySet<Person>(context, "Person")
.orderedBy(.name, ascending: true)
.filter(\.age >= 18)
QuerySet
A QuerySet represents a collection of objects from your Core Data Store. It may have zero, one or many filters. Filters narrow down the query results based on the given parameters.
Retrieving all objects
let queryset = QuerySet<Person>(context, "Person")
Retrieving specific objects with filters
You may filter a QuerySet using the filter and exclude methods, which accept a predicate which can be constructed using KeyPath extensions.
The filter and exclude methods return new QuerySet's including your filter.
queryset.filter(\.name == "Kyle")
queryset.exclude(\.age > 25)
You may also use standard NSPredicate if you want to construct complicated queries or do not wish to use the type-safe properties.
queryset.filter(NSPredicate(format: "name == '%@'", "Kyle"))
queryset.exclude(NSPredicate(format: "age > 25"))
Chaining filters
The result of refining a QuerySet is itself a QuerySet, so it’s possible to chain refinements together. For example:
queryset.filter(\.name == "Kyle")
.exclude(\.age < 25)
Each time you refine a QuerySet, you get a new QuerySet instance that is in no way bound to the previous QuerySet. Each refinement creates a separate and distinct QuerySet that may be stored, used and reused.
QuerySets are lazy
A QuerySet is lazy, creating a QuerySet doesn’t involve querying Core Data. QueryKit won’t actually execute the query until the QuerySet is evaluated.
Ordering
You may order a QuerySet's results by using the orderBy function which accepts a KeyPath.
queryset.orderBy(\.name, ascending: true)
You may also pass in an NSSortDescriptor if you would rather.
queryset.orderBy(NSSortDescriptor(key: "name", ascending: true))
Slicing
Using slicing, a QuerySet's results may be limited to a specified range. For example, to get the first 5 items in our QuerySet:
queryset[0...5]
NOTE: Remember, QuerySets are lazily evaluated. Slicing doesn’t evaluate the query.
Fetching
Multiple objects
You may convert a QuerySet to an array using the array() function. For example:
for person in try! queryset.array() {
println("Hello \(person.name).")
}
First object
let kyle = try? queryset.first()
Last object
let kyle = try? queryset.last()
Object at index
let katie = try? queryset.object(3)
Count
let numberOfPeople = try? queryset.count()
Deleting
This method immediately deletes the objects in your queryset and returns a count or an error if the operation failed.
let deleted = try? queryset.delete()
Operators
QueryKit provides KeyPath extensions providing operator functions allowing you to create predicates.
// Name is equal to Kyle
\Person.name == "Kyle"
// Name is either equal to Kyle or Katie
\.Person.name << ["Kyle", "Katie"]
// Age is equal to 27
\.Person.age == 27
// Age is more than or equal to 25
\Person.age >= 25
// Age is within the range 22 to 30.
\Person.age << (22...30)
The following types of comparisons are supported using Attribute:
| Comparison | Meaning |
|---|---|
| == | x equals y |
| != | x is not equal to y |
| < | x is less than y |
| <= | x is less than or equal to y |
| > | x is more than y |
| >= | x is more than or equal to y |
| ~= | x is like y |
| ~= | x is like y |
| << | x IN y, where y is an array |
| << | x BETWEEN y, where y is a range |
Predicate extensions
QueryKit provides the !, && and || operators for joining multiple predicates together.
// Persons name is Kyle or Katie
\Person.name == "Kyle" || \Person.name == "Katie"
// Persons age is more than 25 and their name is Kyle
\Person.age >= 25 && \Person.name == "Kyle"
// Persons name is not Kyle
!(\Person.name == "Kyle")
Installation
CocoaPods is the recommended way to add QueryKit to your project, you may also use Carthage.
pod 'QueryKit'
License
QueryKit is released under the BSD license. See LICENSE.
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