debugging-instruments

Diagnose crashes, memory leaks, retain cycles, main thread hangs, and performance bottlenecks in iOS apps using LLDB, Memory Graph Debugger, and Instruments. Covers breakpoint workflows, memory graph analysis, hang detection, build failure triage, and Instruments profiling for CPU, memory, energy, and network. Use v over po when you only need a local variable value — it does not execute code and cannot trigger side effects. After modifying a view property in the debugger, call CATransaction.flush() to see the change immediately without resuming execution. Watchpoints are hardware-backed (limited to ~4 on ARM). Use them to find unexpected mutations — the debugger stops at the exact line that changes the value. Set breakpoints on methods without knowing the file. Useful for framework or system code: In Xcode, use the Breakpoint Navigator (+) to add symbolic breakpoints for common diagnostics like -[UIApplication main] or swift_willThrow .