Agent skill · software engineering · thebushidocollective
Objective-C Blocks and GCD
Use when blocks (closures) and Grand Central Dispatch in Objective-C for concurrent programming including block syntax, capture semantics, dispatch queues, dispatch groups, and patterns for thread-safe asynchronous code.
Why this skill is useful
Provides specific patterns and syntax for using blocks and GCD in Objective-C that the AI wouldn't reliably generate on its own.
What it needs
About 8k tokens when loaded. Last updated 2026-07-19. 187 stars on the source repository.
What this skill does
Objective-C Blocks and GCD Introduction Blocks are Objective-C's closure implementation, providing anonymous functions that capture surrounding context. Grand Central Dispatch (GCD) is Apple's low-level API for managing concurrent operations using dispatch queues rather than threads directly. Blocks enable functional programming patterns, callbacks, and clean asynchronous API design. GCD simplifies concurrency by abstracting thread management into queues that automatically distribute work across available CPU cores. Together, they form the foundation for modern Objective-C concurrent programming. This skill covers block syntax and semantics, capture behavior, GCD queues and dispatch functions, synchronization primitives, and patterns for safe concurrent code. Block Syntax and Usage Blocks are first-class objects that encapsulate code and can capture variables from their defining scope. Blocks must be copied when stored in properties or collections to move them from stack to heap storage. Block Capture Semantics Blocks capture variables from their defining scope, with different behaviors for different storage types and qualifiers. Use weak to avoid retain cycles when capturing self, and block to allow mutation of captured variables. Dispatch Queues GCD uses dispatch queues to manage concurrent execution, with serial queues executing tasks sequentially and concurrent queues executing them in parallel. Use main queue for UI updates, global queues for background work, and custom queues for synchronization and ordered execution. Dispatch Groups Dispatch groups coordinate multiple async operations, notifying when all tasks complete. Dispatch groups are essential for coordinating multiple async operations and ensuring all complete before proceeding. Dispatch Barriers and Synchronization Barriers provide synchronized access to shared resources in concurrent queues. …
How to use it
Reference it in AdaL, Claude Code, Cursor or any coding agent — nothing to install:
@skills thebushidocollective/objc-blocks-gcd