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.

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.