Class-Definition Data Structures
Class
An opaque type that represents an Objective-C class.
Method
An opaque type that represents a method in a class definition.
Ivar
An opaque type that represents an instance variable.
Category
An opaque type that represents a category.
objc_property_t
An opaque type that represents an Objective-C declared property.
IMP
A pointer to the start of a method implementation.
SEL
Defines an opaque type that represents a method selector.
objc_cache
Performance optimization for method calls. Contains pointers to recently used methods.