Objective-C underlying data structure

Objective-C underlying data structure

Objective-C underlying data structure

Class Data Structure

Class (pointer)

Typedef struct objc_class * class;/* this is the data structure generated by the compiler for each class. This structure defines a class. this structure is generated by the compiler during execution and used to send messages during runtime. therefore, some members change the type. the compiler generates a "char * const" string pointer instead of the following member variable "super_class" */struct objc_class {struct objc_class * class_pointer;/* pointer to the metaclass. */struct objc_class * super_class;/* pointer to the parent class. nsobject is null. */const char * Name;/* class name. */long version;/* unknown. */unsigned long Info;/* bit mask. refer to the mask definition of the following class. */long instance_size;/* number of bytes of the class. includes the definition of classes and all parent classes */# ifdef _ win64 long pad; # endif struct objc_ivar_list * ivars;/* points to the list structure of instance variables defined in the class. null indicates that no instance variable exists. does not include the variables of the parent class. */struct objc_method_list * methods;/* The instance method defined in the Link class. */struct sarray * dtable;/* points to the instance method allocation table. */struct objc_class * subclass_list;/* parent class list */struct objc_class * sibling_class; struct objc_protocol_list * protocols;/* Target prototype list */void * gc_object_type ;};

Method (pointer)

Typedef struct objc_method * method;/* the compiler generates one or more such structures for the class based on the methods defined in the class. the implementation of a class can be dispersed in different parts of a file, and classes can be dispersed in different modules. to solve this problem, use a separate method linked list */struct objc_method {sel method_name;/* this variable is the name of the method. the compiler uses a 'Char * 'here. When a method is registered, the name is replaced by a real sel */const char * method_types during runtime; /* List of parameters used to describe the method. used when the selector is registered at runtime. at that time, the method name will contain a list of parameters of the method. */IMP method_imp;/* address of the method execution. */};

Ivar (pointer)

Typedef struct objc_ivar * Ivar;/* the compiler generates one or more such structures for the Class Based on the instance variables defined in the class */struct objc_ivar {const char * ivar_name; /* variable name defined in the class. */const char * ivar_type;/* describes the variable type. debugging is very useful. */INT ivar_offset;/* base address offset byte of the Instance structure */};

Category (pointer)

Typedef struct objc_category * category;/* the compiler generates such a structure for each category. A class can have multiple classes, including both the instance method and the class Method */struct objc_category {const char * category_name;/* class name. define */const char * class_name;/* class name */struct objc_method_list * instance_methods;/* The instance method defined in the Link class. null indicates no instance method. */struct objc_method_list * class_methods;/* class methods defined in the Link class. null indicates no class method. */struct objc_protocol_list * protocols;/* protocol table */};

Objc_property_t

typedef struct objc_property *objc_property_t;

IMP

id (*IMP)(id, SEL, ...)

Sel

typedef struct objc_selector *SEL;  struct objc_selector{  void *sel_id;  const char *sel_types;};

Objc_method_list

Struct objc_method_list {struct objc_method_list * method_next;/* this variable is used to link another independent method linked list */INT method_count; /* Number of methods defined in the Structure */struct objc_method method_list [1];/* variable length structure */};

Objc_cache

struct objc_cache{    unsigned int mask;    unsigned int occupied;    Method buckets[1];};

Objc_protocol_list

struct objc_protocol_list{  struct objc_protocol_list *next;  size_t count;  struct objc_protocol *list[1];};

Data Structure ID of the Instance

typedef struct objc_object *id;

Objc_object

Struct objc_object {/* class pointer is an object-related class. If it is a class object, this pointer points to the Meta class. Class ISA ;};

Objc_super

Struct objc_super {ID self;/* receiver of the Message */class super_class;/* parent class of the receiver */};

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Objective-C underlying data structure