Pistachio
Pistachio is a generic model framework. By leveraging lenses and value transformers, it allows you to create type safe adapters for any recursive data structure, be it JSON, YAML or XML.
If you are already familiar with Argo, take a look at Pistachiargo.
Installation
Carthage
Carthage is a simple, decentralized dependency manager for Cocoa.
- Add Pistachio to your Cartfile:
github "felixjendrusch/Pistachio" ~> 0.2
-
Run
carthage updateto fetch and build Pistachio and its dependencies.
Usage
Let's start by defining a very simple model:
struct Origin {
var city: String
init(city: String = "") {
self.city = city
}
}struct Person {
var name: String
var origin: Origin
init(name: String = "", origin: Origin = Origin()) {
self.name = name
self.origin = origin
}
}A lens is basically just a combination of a getter and a setter, providing a view on your model:
struct OriginLenses {
static let city = Lens(get: { $0.city }, set: { (inout origin: Origin, city) in
origin.city = city
})
}struct PersonLenses {
static let name = Lens(get: { $0.name }, set: { (inout person: Person, name) in
person.name = name
})
static let origin = Lens(get: { $0.origin }, set: { (inout person: Person, origin) in
person.origin = origin
})
}It can be used to access and modify your model:
var person = Person(name: "Felix", origin: Origin(city: "Berlin"))
person = set(PersonLenses.name, person, "Robb")
get(PersonLenses.name, person) // == "Robb"And you can compose, lift, etc. them:
let composed = PersonLenses.origin >>> OriginLenses.city
person = set(composed, person, "New York")
get(composed, person) // == "New York"With lenses and value transformers, you can create adapters for your models:
struct Adapters {
static let origin = DictionaryAdapter(specification: [
"city_name": map(OriginLenses.city, StringToAnyObjectValueTransformers)
], dictionaryTansformer: DictionaryToAnyObjectValueTransformers, value: Origin())
static let person = DictionaryAdapter(specification: [
"name": map(PersonLenses.name, StringToAnyObjectValueTransformers),
"origin": map(PersonLenses.origin, origin)
], dictionaryTansformer: DictionaryToAnyObjectValueTransformers, value: Person())
}Use fix to create adapters for recursive models:
let adapter: DictionaryAdapter<Key, Value, TransformedValue, Error> = fix { adapter in
// use `adapter` to reference the currently created adapter
}Adapters handle transforming and reverse transforming your models:
let adapter = Adapters.person
var person = Person(name: "Seb", origin: Origin(city: "Berlin"))
var data = adapter.transform(person)
// == .Success(Box([ "name": "Seb", "origin": [ "city_name": "Berlin" ] ]))
adapter.reverseTransform(data.value!)
// == .Success(Box(person))Both transform and reverseTransform return a Result, which either holds the (reverse) transformed value or an error. This enables you to gracefully handle transformation errors.
Posts
- Working with immutable models in Swift (February 14, 2015)