CargoBay
The Essential StoreKit Companion
...It provides one-step receipt and transaction verification following Apple’s recommended server validation flow. Product information can be requested with block-based callbacks from local identifiers or identifiers supplied by a remote service. Payment queue observer methods are exposed as blocks, reducing the need for repetitive delegate code. The library automatically checks transaction uniqueness to help prevent the same purchase from being processed twice. A shared manager coordinates product lookup, payment events, and receipt verification across the application. CargoBay is MIT-licensed, archived, and no longer maintained, so it mainly serves as a legacy reference for StoreKit integrations.