Predicates.swift

Predicates.swift is a Swift package that aims to create predicates that can filter Swift objects in a type-safe manner based on KeyPaths.

The goal is to also provide converters to popular filtering tools like NSPredicate and SQL when possible.

Example Usage

Given the following sample struct and data:

struct Person: Equatable {
    let name: String
    var age: Int
    var isDead: Bool
}

let majd = Person(name: "Majd", age: 24, isDead: false)
let nidal = Person(name: "Nidal", age: 16, isDead: false)
let john = Person(name: "John", age: 70, isDead: false)
let thaer = Person(name: "Thaer", age: 17, isDead: true)

let people = [
    majd,
    nidal,
    john,
    thaer,
]

You can build a predicate for a specific type by simply comparing a particular keyPath to some value:

let adultPredicate = \Person.age > 18

And then you can use that predicate to evaluate a single person:

adultPredicate.evaluate(majd) // true
adultPredicate.evaluate(nidal) // false

Or filter the array:

people.filter(adultPredicate) // [majd, john]

You can also create more complicated predicates using the regular &&, ||, and ! operators:

let eligibleForFreeMedicationPredicate = (\Person.age < 18 || \Person.age > 65) && !\Person.isDead
people.filter(eligibleForFreeMedicationPredicate) // [nidal, john]