TABResourceLoader

This library is designed to fetch resources in a consistent and modular way. The user can define resources by conforming to protocols that define where and how to get them. These resources can then be retrieved using a generic service type with or without an operation provided by the library. By following this approach it's easy to have testable and modular networking stack.

Installation

Swift Package Manager

You can add TABResourceLoader as a remote Swift Package dependency in Xcode 11 or newer.

Cocoapods

To use the latest version of TABResourceLoader just add this to your Podfile and run pod update or pod install in Terminal:

pod 'TABResourceLoader'

Example use cases

Working with a web service

• Retrieving a Decodable object
• Retrieving a JSON object
• Retrieving an image
• Responding to network activity
• [Using failure model example](Documentation/Using failure models.md)

High level architecture

This library defines/uses 4 concepts: model, resource, service and operation:

1. Model: Strongly typed object in your codebase, may or may not be mapped 121 to the server model
2. Resource: Defines through protocol conformance where and how to fetch a Model. For example a resource could define the URL of where a JSON file is and how to parse into strongly types model.
3. Service: A type that knows how to retrieve a specific kind of Resource
4. Operation: Provides a concurrency model when using a Service. Useful when implementing custom business logic such as throttling of fetches.

Resource protocols

Root protocols

• ResourceType: Defines a generic Model
• NetworkResourceType: Defines how an endpoint can be accessed. By specifying the following properties:
  • URL (Required)
  • HTTP method (Optional, default GET)
  • HTTP header fields (Optional)
  • Body of request (JSON encoded) (Optional)
  • URL query strings (Optional)

Conforming to ResourceType

• DataResourceType: Defines a resource that can create a generic Model from (NS)Data

Conforming to DataResourceType

• JSONDecodableResourceType: Defines the transformation from a JSON response into an object that conforms to Decodable
• JSONDictionaryResourceType: Defines the transformation from a JSON object, i.e. [String: Any] to a generic Model
• JSONArrayResourceType : Defines the transformation from a JSON array, i.e. [Any] to a generic Model
• ImageResourceType: Defines the transformation from (NS)Data to a UIImage
• PropertyListDecodableResourceType:

Protocols that inherit from multiple protocols

• NetworkJSONDictionaryResourceType: Combines JSONDictionaryResourceType and NetworkResourceType to allow for retrieving a generic Model from a JSON dictionary from a web service.
• NetworkJSONArrayResourceType: Combines JSONArrayResourceType and NetworkResourceType to allow for retrieving a generic Model from a JSON array from a web service.
• NetworkJSONDecodableResourceType: Combines JSONDecodableResourceType and NetworkResourceType to allow for retrieving a generic Model from a JSON response from a web service.

Note: The above all include ["Content-Type": "application/json"] as default header fields.

• NetworkPropertyListDecodableResourceType: Combines PropertyListDecodableResourceType and NetworkResourceType to allow for retrieving a generic Model from a Property List format XML response from a web service. It includes the ["Content-Type": "application/x-plist"] as default header fields.

Concrete types

• NetworkImageResource: Conforms to ImageResourceType and can be initialized with a URL

Services

• NetworkDataResourceService: Used to retrieve a resource that conforms to NetworkResourceType and DataResourceType
  • fetch function returns a Cancellable object which can be used to cancel the network request
  • When the network request finishes a completion handler is called with a NetworkResponse<Model> enum
• GenericNetworkDataResourceService: Inherits NetworkDataResourceService and conforms toResourceServiceType. The purpose of this service is to be use with ResourceOperation

ResourceOperation

• Uses a service that conforms to ResourceServiceType to retrieve a resource that conforms to ResourceType
• Subclass of (NS)Operation used to retrieve a resource with specific service
• Uses a completion handler when the operation is finished to pass it's Result

Contributing

Guidelines for contributing can be found here.

Author

Luciano Marisi @lucianomarisi

The original idea for this pattern is explained on Protocol oriented loading of resources from a network service in Swift

License

TABResourceLoader is available under the MIT license. See the LICENSE file for more info.