By setting environment variables, we can quickly see the configuration of the project

Setting environment Variables

createLGPersonandLGTeacherTwo classes, and implementationloadmethods

Command + R Displays logs

When we implement the load method in the class we create, we will print the class that implements the load method in the process of running the program. Through this method, we can quickly locate the class that implements the load method in the project.

Common environment variables

DYLD_PRINT_STATISTICS: Monitors and prints the application startup time

OBJC_PRINT_LOAD_METHODS: Prints the classes that implement the load method

OBJC_PRINT_IMAGES: log image and library names as they are loaded

OBJC_PRINT_IMAGE_TIMES: measure duration of image loading steps

OBJC_PRINT_LOAD_METHODS: log calls to class and category +load methods

OBJC_PRINT_INITIALIZE_METHODS: log calls to class +initialize methods

OBJC_PRINT_RESOLVED_METHODS: log methods created by +resolveClassMethod: and +resolveInstanceMethod:

OBJC_PRINT_CLASS_SETUP: log progress of class and category setup

OBJC_PRINT_PROTOCOL_SETUP: log progress of protocol setup

OBJC_PRINT_IVAR_SETUP: log processing of non-fragile ivars

OBJC_PRINT_VTABLE_SETUP: log processing of class vtables

OBJC_PRINT_VTABLE_IMAGES: print vtable images showing overridden methods

OBJC_PRINT_CACHE_SETUP: log processing of method caches

OBJC_PRINT_FUTURE_CLASSES: log use of future classes for toll-free bridging

OBJC_PRINT_PREOPTIMIZATION: log preoptimization courtesy of dyld shared cache

OBJC_PRINT_CXX_CTORS: log calls to C++ ctors and dtors for instance variables

OBJC_PRINT_EXCEPTIONS: log exception handling

OBJC_PRINT_EXCEPTION_THROW: log backtrace of every objc_exception_throw()

OBJC_PRINT_ALT_HANDLERS: log processing of exception alt handlers

OBJC_PRINT_REPLACED_METHODS: log methods replaced by category implementations

OBJC_PRINT_DEPRECATION_WARNINGS: warn about calls to deprecated runtime functions

OBJC_PRINT_POOL_HIGHWATER: log high-water marks for autorelease pools

OBJC_PRINT_CUSTOM_CORE: log classes with custom core methods

OBJC_PRINT_CUSTOM_RR: log classes with custom retain/release methods

OBJC_PRINT_CUSTOM_AWZ: log classes with custom allocWithZone methods

OBJC_PRINT_RAW_ISA: log classes that require raw pointer isa fields

OBJC_DEBUG_UNLOAD: warn about poorly-behaving bundles when unloaded

OBJC_DEBUG_FRAGILE_SUPERCLASSES: warn about subclasses that may have been broken by subsequent changes to superclasses

OBJC_DEBUG_NIL_SYNC: warn about @synchronized(nil), which does no synchronization

OBJC_DEBUG_NONFRAGILE_IVARS: capriciously rearrange non-fragile ivars

OBJC_DEBUG_ALT_HANDLERS: record more info about bad alt handler use

OBJC_DEBUG_MISSING_POOLS: warn about autorelease with no pool in place, which may be a leak

OBJC_DEBUG_POOL_ALLOCATION: halt when autorelease pools are popped out of order, and allow heap debuggers to track autorelease pools

OBJC_DEBUG_DUPLICATE_CLASSES: halt when multiple classes with the same name are present

OBJC_DEBUG_DONT_CRASH: halt the process by exiting instead of crashing

OBJC_DISABLE_VTABLES: disable vtable dispatch

OBJC_DISABLE_PREOPTIMIZATION: disable preoptimization courtesy of dyld shared cache

OBJC_DISABLE_TAGGED_POINTERS: disable tagged pointer optimization of NSNumber et al.

OBJC_DISABLE_TAG_OBFUSCATION: disable obfuscation of tagged pointers

OBJC_DISABLE_NONPOINTER_ISA: disable non-pointer isa fields

OBJC_DISABLE_INITIALIZE_FORK_SAFETY: disable safety checks for +initialize after fork