Enceladus

Enceladus is a Swift-based framework designed to stream cached and network results with a simple API.

Features

• Local caching using SwiftData.
• Built-in polling. As long as a stream is active for a given query/ model, it is fetched and emitted at the interval specified by each model
• Stream models by unique identifier or as a singleton
• Stream lists of models based on query and sort descriptors. Queries are transformed into SwiftData predicates.
• Fetch models asynchronously using async/await.

Installation

Swift Package Manager

To integrate Enceladus into your Xcode project using Swift Package Manager, add the following to your Package.swift:

dependencies: [
    .package(url: "https://github.com/lekom/Enceladus.git", from: "1.0.0")
]

Usage

Protocol Definition

Enceladus provides the ModelProviding protocol that outlines the methods for fetching models.

import Combine
import Foundation

public protocol ModelProviding {

    func streamModel<T: BaseModel>(_ modelType: T.Type, id: String) -> AnyPublisher<ModelQueryResult<T>, Never>
    func streamModel<T: SingletonModel>(modelType: T.Type) -> AnyPublisher<ModelQueryResult<T>, Never>
    func streamFirstModel<T: ListModel>(_ modelType: T.Type, query: ModelQuery<T>?, sortDescriptors: [SortDescriptor<T>]?) -> AnyPublisher<ModelQueryResult<T>, Never>
    func streamModels<T: ListModel>(_ modelType: T.Type, query: ModelQuery<T>?, limit: Int?, sortDescriptors: [SortDescriptor<T>]?) -> AnyPublisher<ListQueryResult<T>, Never>

    func getModel<T: BaseModel>(_ modelType: T.Type, id: String) async -> Result<T, Error>
    func getModel<T: SingletonModel>(_ modelType: T.Type) async -> Result<T, Error>
    func getFirstModel<T: ListModel>(_ modelType: T.Type, query: ModelQuery<T>?, sortDescriptors: [SortDescriptor<T>]?) async -> Result<T, Error>
    func getList<T: ListModel>(_ modelType: T.Type, query: ModelQuery<T>?, limit: Int?, sortDescriptors: [SortDescriptor<T>]?) async -> Result<[T], Error>

    func configure(headersProvider: (() -> [String: String])?)
}

Accessing the Model Provider

You can access the model provider using the getModelProvider() function. This function returns an instance that conforms to the ModelProviding protocol.

let modelProvider = getModelProvider()

Providing Headers for Network Requests

Call getModelProvider().configure(headersProvider... once at app launch to ensure any required headers are sent with each network request. The provided headersProvider closure is called on each network request and the returned headers are not cached by this lib between network requests.

getModelProvider().configure(headersProvider: { ["authorization": "abc"] })

Unit Testing

For unit testing, you can override the default model provider returned from getModelProvider() by setting a global variable mockedModelProvider. Set it to any mock instance that adopts the ModelProviding protocol. MockModelProvider is provided for convenience in the EnceladusMocks target for use in testing.

var mockedModelProvider: ModelProviding?

func getModelProvider() -> ModelProviding {
    return mockedModelProvider ?? DefaultModelProvider()
}

Example Usage

Streaming a Model by ID

modelProvider.streamModel(MyModel.self, id: "123")
    .sink { result in
        switch result {
        case .loading:
            print("model is being fetched from the network")
        case .loaded(let model)
            print("Model: \(model) found as either a freshly cached item or result of a network request")
        case .error(let error):
            print("Error: \(error) occured while fetching the model")
        }
    }
    .store(in: &cancellables)

Fetching a Model Asynchronously

let result = await modelProvider.getModel(MyModel.self, id: "123")
switch result {
case .success(let model):
    print("Model: \(model)")
case .failure(let error):
    print("Error: \(error)")
}

Contributing

Contributions are welcome! Please open an issue or submit a pull request.