iOS runtime浅析Property和Ivar

iOS>runtime

Property

property 是Objective-C的一个语法糖，能帮助你声明成员变量(ivar)(自动声明的变量名前面会加下划线)+自动生成对应属性特性(atomic/nonatomic/copy/strong/weak/assign...)的setter和getter

通常我们在编写iOS程序的时候声明类的成员变量，习惯使用property。

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//
//  GMYTestObject.h
//  ObjectInspector
//
//  Created by miaoyou.gmy on 2017/2/22.
//  Copyright © 2017年 miaoyou.gmy. All rights reserved.
//
@interface GMYTestObject : NSObject
@property (nonatomic, assign) NSUInteger index;
@property (nonatomic, copy) NSString *str;
@property (nonatomic, copy) NSArray *array;
@end

对应自动声明的_index，_str，_array

若想声明private的成员变量要借助Class Extensions在原有的实现文件中添加变量。

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//
//  GMYTestObject.m
//  ObjectInspector
//
//  Created by miaoyou.gmy on 2017/2/22.
//  Copyright © 2017年 miaoyou.gmy. All rights reserved.
//

#import "GMYTestObject.h"

@interface GMYTestObject ()
@property (nonatomic, copy) NSString *testStr;
@property (nonatomic, assign) CGFloat margin;
@property (nonatomic, copy) NSDictionary *dict;
@end

@implementation GMYTestObject
@end

这个技巧可以参阅Class Extensions Extend the Internal Implementation

题外话

property在早些年是不支持声明类变量的。直到2016年Xcode8发布和更新了LLVM，才支持。
WWDC 2016 Session 405 What’s New in LLVM

From the Xcode 8 release notes:

Objective-C now supports class properties, which interoperate with Swift type properties. They are declared as: @property (class) NSString *someStringProperty;. They are never synthesized. (23891898)

额外要注意是，使用property声明类变量是不会自动合成setter 和 getter 的。They are never synthesized.

要使用这个特性的具体实践是：
在 .h头文件中声明

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//
//  GMYTestObject.h
//  ObjectInspector
//
//  Created by miaoyou.gmy on 2017/2/22.
//  Copyright © 2017年 miaoyou.gmy. All rights reserved.
//

#import <Foundation/Foundation.h>
@interface GMYTestObject : NSObject
@property (class, nonatomic, assign) NSUInteger instanceCount;
@end

在.m实现文件中声明setter和getter + 声明static 同类型类变量

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//
//  GMYTestObject.m
//  ObjectInspector
//
//  Created by miaoyou.gmy on 2017/2/22.
//  Copyright © 2017年 miaoyou.gmy. All rights reserved.
//

#import "GMYTestObject.h"
@implementation GMYTestObject
static NSUInteger _instanceCount = 0;
+ (NSUInteger)instanceCount{
    return _instanceCount;
}

+ (void)setInstanceCount:(NSUInteger)instanceCount{
    _instanceCount = instanceCount; //  重复声明一个类变量是为了实现setter,加_是自有成员变量的传统命名规则
}
@end

Ivar

Property是Ivar+synthesized setter + synthesized getter 的语法糖
Ivar指的就是instance variables

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@interface GMYTestObject : NSObject{
@public
    NSUInteger _index;
    NSString *_str;
    NSArray *_array;
}

没有自动合成的setter 和 getter方法。在OOP的封装概念下显得不那么讨喜，渐渐被Property取代。

“原始”的Ivar声明方式也有不少好处：why-would-you-use-an-ivar

runtime

我们再来聊聊如何借助iOS的动态性，获取一个对象的所有成员变量。

在<objc/runtime.h>中

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// Describes the properties declared by a class.

OBJC_EXPORT objc_property_t *class_copyPropertyList(Class cls, unsigned int *outCount)
    OBJC_AVAILABLE(10.5, 2.0, 9.0, 1.0);
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// Describes the instance variables declared by a class.

OBJC_EXPORT Ivar *class_copyIvarList(Class cls, unsigned int *outCount) 
    OBJC_AVAILABLE(10.5, 2.0, 9.0, 1.0);

根据Property 和 Ivar 的关系可知。我们使用class_copyIvarList就能获取到所有对象成员变量，包括使用原始声明方式声明的变量。

我们再看看有什么和Ivar相关的API

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//Returns the name of an instance variable.
OBJC_EXPORT const char *ivar_getName(Ivar v);
    
//Returns the type string of an instance variable. 
OBJC_EXPORT const char *ivar_getTypeEncoding(Ivar v);

//Returns the offset of an instance variable.
OBJC_EXPORT ptrdiff_t ivar_getOffset(Ivar v); 
    
//Reads the value of an instance variable in an object.
OBJC_EXPORT id object_getIvar(id obj, Ivar ivar);

//Sets the value of an instance variable in an object.
OBJC_EXPORT void object_setIvar(id obj, Ivar ivar, id value);

定义GMYTestObject作用测试各个类型的成员变量

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//
//  GMYTestObject.h
//  ObjectInspector
//
//  Created by miaoyou.gmy on 2017/2/22.
//  Copyright © 2017年 miaoyou.gmy. All rights reserved.
//

#import <Foundation/Foundation.h>

typedef enum{
    TestA,
    TestB,
    TestC
}TestEnum;

typedef struct{
    float x,y;
}pointNode;

@interface CustomizeObject : NSObject
@property (nonatomic) NSString *name;
@property (nonatomic) NSUInteger age;
@end

@interface GMYTestObject : NSObject
@property (nonatomic) char aChar;
@property (nonatomic) int anInt;
@property (nonatomic) short aShort;
@property (nonatomic) long aLong;
@property (nonatomic) long long aLongLong;
@property (nonatomic) unsigned char anUnsignedChar;
@property (nonatomic) unsigned int anUnsignedInt;
@property (nonatomic) unsigned short anUnsignedShort;
@property (nonatomic) unsigned long anUnsignedLong;
@property (nonatomic) unsigned long long anUnsignedLongLong;
@property (nonatomic) float aFloat;
@property (nonatomic) double aDouble;
@property (nonatomic) BOOL aBooL;
@property (nonatomic) Boolean aBoolean;
@property (nonatomic) bool abool;
@property (nonatomic) char* aCharStar;
@property (nonatomic) int* aIntStar;
@property (nonatomic) void aVoid;
@property (nonatomic) TestEnum aEnum;
@property (nonatomic) pointNode aNode;
@property (nonatomic) SEL aSEL;
@property (nonatomic) id aId;
@property (nonatomic) Class aClass;
@property (nonatomic) NSArray<NSString *> *array;
@property (nonatomic) NSArray<CustomizeObject *> *customizeArray;
@property (nonatomic) NSDictionary *dictionary;
@property (nonatomic) NSSet *aSet;
@property (nonatomic) NSRange range;
@end

使用ivar_getName和ivar_getTypeEncoding 打印结果：

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c _aChar
C _anUnsignedChar
c _aBooL
C _aBoolean
B _abool
s _aShort
S _anUnsignedShort
i _anInt
I _anUnsignedInt
f _aFloat
i _aEnum
q _aLong
q _aLongLong
Q _anUnsignedLong
Q _anUnsignedLongLong
d _aDouble
* _aCharStar
^i _aIntStar
{?="x"f"y"f} _aNode
: _aSEL
@ _aId
# _aClass
@"NSArray" _array
@"NSArray" _customizeArray
@"NSDictionary" _dictionary
@"NSSet" _aSet
{_NSRange="location"Q"length"Q} _range

@note For possible values, see Objective-C Runtime Programming Guide > Type Encodings.

我们还可以更加直观的查看

使用clang rewrite-objc GMYTestObject.m。因为内容过多，这里只放最重要的内容。我们可以清晰的看到 property声明的成员变量是如何定义在C++文件中的。

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#ifndef _REWRITER_typedef_GMYTestObject
#define _REWRITER_typedef_GMYTestObject
typedef struct objc_object GMYTestObject;
typedef struct {} _objc_exc_GMYTestObject;
#endif

extern "C" unsigned long OBJC_IVAR_$_GMYTestObject$_aId;
extern "C" unsigned long OBJC_IVAR_$_GMYTestObject$_aBoolean;
extern "C" unsigned long OBJC_IVAR_$_GMYTestObject$_dictionary;
extern "C" unsigned long OBJC_IVAR_$_GMYTestObject$_aEnum;
extern "C" unsigned long OBJC_IVAR_$_GMYTestObject$_anUnsignedChar;
extern "C" unsigned long OBJC_IVAR_$_GMYTestObject$_anInt;
extern "C" unsigned long OBJC_IVAR_$_GMYTestObject$_aFloat;
extern "C" unsigned long OBJC_IVAR_$_GMYTestObject$_abool;
extern "C" unsigned long OBJC_IVAR_$_GMYTestObject$_aSEL;
extern "C" unsigned long OBJC_IVAR_$_GMYTestObject$_aNode;
extern "C" unsigned long OBJC_IVAR_$_GMYTestObject$_customizeArray;
extern "C" unsigned long OBJC_IVAR_$_GMYTestObject$_aLongLong;
extern "C" unsigned long OBJC_IVAR_$_GMYTestObject$_aChar;
extern "C" unsigned long OBJC_IVAR_$_GMYTestObject$_aCharStar;
extern "C" unsigned long OBJC_IVAR_$_GMYTestObject$_aDouble;
extern "C" unsigned long OBJC_IVAR_$_GMYTestObject$_anUnsignedShort;
extern "C" unsigned long OBJC_IVAR_$_GMYTestObject$_range;
extern "C" unsigned long OBJC_IVAR_$_GMYTestObject$_aLong;
extern "C" unsigned long OBJC_IVAR_$_GMYTestObject$_anUnsignedLong;
extern "C" unsigned long OBJC_IVAR_$_GMYTestObject$_array;
extern "C" unsigned long OBJC_IVAR_$_GMYTestObject$_aIntStar;
extern "C" unsigned long OBJC_IVAR_$_GMYTestObject$_aBooL;
extern "C" unsigned long OBJC_IVAR_$_GMYTestObject$_anUnsignedInt;
extern "C" unsigned long OBJC_IVAR_$_GMYTestObject$_aSet;
extern "C" unsigned long OBJC_IVAR_$_GMYTestObject$_aShort;
extern "C" unsigned long OBJC_IVAR_$_GMYTestObject$_anUnsignedLongLong;
extern "C" unsigned long OBJC_IVAR_$_GMYTestObject$_aClass;
struct GMYTestObject_IMPL {
	struct NSObject_IMPL NSObject_IVARS;
	char _aChar;
	unsigned char _anUnsignedChar;
	BOOL _aBooL;
	Boolean _aBoolean;
	bool _abool;
	short _aShort;
	unsigned short _anUnsignedShort;
	int _anInt;
	unsigned int _anUnsignedInt;
	float _aFloat;
	TestEnum _aEnum;
	long _aLong;
	long long _aLongLong;
	unsigned long _anUnsignedLong;
	unsigned long long _anUnsignedLongLong;
	double _aDouble;
	char *_aCharStar;
	int *_aIntStar;
	pointNode _aNode;
	SEL _aSEL;
	id _aId;
	Class _aClass;
	NSArray<NSString *> *_array;
	NSArray<CustomizeObject *> *_customizeArray;
	NSDictionary *_dictionary;
	NSSet *_aSet;
	NSRange _range;
};

// @property (nonatomic) char aChar;
// @property (nonatomic) int anInt;
// @property (nonatomic) short aShort;
// @property (nonatomic) long aLong;
// @property (nonatomic) long long aLongLong;
// @property (nonatomic) unsigned char anUnsignedChar;
// @property (nonatomic) unsigned int anUnsignedInt;
// @property (nonatomic) unsigned short anUnsignedShort;
// @property (nonatomic) unsigned long anUnsignedLong;
// @property (nonatomic) unsigned long long anUnsignedLongLong;
// @property (nonatomic) float aFloat;
// @property (nonatomic) double aDouble;
// @property (nonatomic) BOOL aBooL;
// @property (nonatomic) Boolean aBoolean;
// @property (nonatomic) bool abool;
// @property (nonatomic) char* aCharStar;
// @property (nonatomic) int* aIntStar;
// @property (nonatomic) void aVoid;
// @property (nonatomic) TestEnum aEnum;
// @property (nonatomic) pointNode aNode;
// @property (nonatomic) SEL aSEL;
// @property (nonatomic) id aId;
// @property (nonatomic) Class aClass;
// @property (nonatomic) NSArray<NSString *> *array;
// @property (nonatomic) NSArray<CustomizeObject *> *customizeArray;
// @property (nonatomic) NSDictionary *dictionary;
// @property (nonatomic) NSSet *aSet;
// @property (nonatomic) NSRange range;
/* @end */


// @implementation GMYTestObject
// @dynamic aVoid;

static instancetype _I_GMYTestObject_init(GMYTestObject * self, SEL _cmd) {
    self = ((GMYTestObject *(*)(__rw_objc_super *, SEL))(void *)objc_msgSendSuper)((__rw_objc_super){(id)self, (id)class_getSuperclass(objc_getClass("GMYTestObject"))}, sel_registerName("init"));
    if(self){

    }
    return self;
}




static char _I_GMYTestObject_aChar(GMYTestObject * self, SEL _cmd) { return (*(char *)((char *)self + OBJC_IVAR_$_GMYTestObject$_aChar)); }
static void _I_GMYTestObject_setAChar_(GMYTestObject * self, SEL _cmd, char aChar) { (*(char *)((char *)self + OBJC_IVAR_$_GMYTestObject$_aChar)) = aChar; }

static int _I_GMYTestObject_anInt(GMYTestObject * self, SEL _cmd) { return (*(int *)((char *)self + OBJC_IVAR_$_GMYTestObject$_anInt)); }
static void _I_GMYTestObject_setAnInt_(GMYTestObject * self, SEL _cmd, int anInt) { (*(int *)((char *)self + OBJC_IVAR_$_GMYTestObject$_anInt)) = anInt; }

static short _I_GMYTestObject_aShort(GMYTestObject * self, SEL _cmd) { return (*(short *)((char *)self + OBJC_IVAR_$_GMYTestObject$_aShort)); }
static void _I_GMYTestObject_setAShort_(GMYTestObject * self, SEL _cmd, short aShort) { (*(short *)((char *)self + OBJC_IVAR_$_GMYTestObject$_aShort)) = aShort; }

static long _I_GMYTestObject_aLong(GMYTestObject * self, SEL _cmd) { return (*(long *)((char *)self + OBJC_IVAR_$_GMYTestObject$_aLong)); }
static void _I_GMYTestObject_setALong_(GMYTestObject * self, SEL _cmd, long aLong) { (*(long *)((char *)self + OBJC_IVAR_$_GMYTestObject$_aLong)) = aLong; }

static long long _I_GMYTestObject_aLongLong(GMYTestObject * self, SEL _cmd) { return (*(long long *)((char *)self + OBJC_IVAR_$_GMYTestObject$_aLongLong)); }
static void _I_GMYTestObject_setALongLong_(GMYTestObject * self, SEL _cmd, long long aLongLong) { (*(long long *)((char *)self + OBJC_IVAR_$_GMYTestObject$_aLongLong)) = aLongLong; }

static unsigned char _I_GMYTestObject_anUnsignedChar(GMYTestObject * self, SEL _cmd) { return (*(unsigned char *)((char *)self + OBJC_IVAR_$_GMYTestObject$_anUnsignedChar)); }
static void _I_GMYTestObject_setAnUnsignedChar_(GMYTestObject * self, SEL _cmd, unsigned char anUnsignedChar) { (*(unsigned char *)((char *)self + OBJC_IVAR_$_GMYTestObject$_anUnsignedChar)) = anUnsignedChar; }

static unsigned int _I_GMYTestObject_anUnsignedInt(GMYTestObject * self, SEL _cmd) { return (*(unsigned int *)((char *)self + OBJC_IVAR_$_GMYTestObject$_anUnsignedInt)); }
static void _I_GMYTestObject_setAnUnsignedInt_(GMYTestObject * self, SEL _cmd, unsigned int anUnsignedInt) { (*(unsigned int *)((char *)self + OBJC_IVAR_$_GMYTestObject$_anUnsignedInt)) = anUnsignedInt; }

static unsigned short _I_GMYTestObject_anUnsignedShort(GMYTestObject * self, SEL _cmd) { return (*(unsigned short *)((char *)self + OBJC_IVAR_$_GMYTestObject$_anUnsignedShort)); }
static void _I_GMYTestObject_setAnUnsignedShort_(GMYTestObject * self, SEL _cmd, unsigned short anUnsignedShort) { (*(unsigned short *)((char *)self + OBJC_IVAR_$_GMYTestObject$_anUnsignedShort)) = anUnsignedShort; }

static unsigned long _I_GMYTestObject_anUnsignedLong(GMYTestObject * self, SEL _cmd) { return (*(unsigned long *)((char *)self + OBJC_IVAR_$_GMYTestObject$_anUnsignedLong)); }
static void _I_GMYTestObject_setAnUnsignedLong_(GMYTestObject * self, SEL _cmd, unsigned long anUnsignedLong) { (*(unsigned long *)((char *)self + OBJC_IVAR_$_GMYTestObject$_anUnsignedLong)) = anUnsignedLong; }

static unsigned long long _I_GMYTestObject_anUnsignedLongLong(GMYTestObject * self, SEL _cmd) { return (*(unsigned long long *)((char *)self + OBJC_IVAR_$_GMYTestObject$_anUnsignedLongLong)); }
static void _I_GMYTestObject_setAnUnsignedLongLong_(GMYTestObject * self, SEL _cmd, unsigned long long anUnsignedLongLong) { (*(unsigned long long *)((char *)self + OBJC_IVAR_$_GMYTestObject$_anUnsignedLongLong)) = anUnsignedLongLong; }

static float _I_GMYTestObject_aFloat(GMYTestObject * self, SEL _cmd) { return (*(float *)((char *)self + OBJC_IVAR_$_GMYTestObject$_aFloat)); }
static void _I_GMYTestObject_setAFloat_(GMYTestObject * self, SEL _cmd, float aFloat) { (*(float *)((char *)self + OBJC_IVAR_$_GMYTestObject$_aFloat)) = aFloat; }

static double _I_GMYTestObject_aDouble(GMYTestObject * self, SEL _cmd) { return (*(double *)((char *)self + OBJC_IVAR_$_GMYTestObject$_aDouble)); }
static void _I_GMYTestObject_setADouble_(GMYTestObject * self, SEL _cmd, double aDouble) { (*(double *)((char *)self + OBJC_IVAR_$_GMYTestObject$_aDouble)) = aDouble; }

static BOOL _I_GMYTestObject_aBooL(GMYTestObject * self, SEL _cmd) { return (*(BOOL *)((char *)self + OBJC_IVAR_$_GMYTestObject$_aBooL)); }
static void _I_GMYTestObject_setABooL_(GMYTestObject * self, SEL _cmd, BOOL aBooL) { (*(BOOL *)((char *)self + OBJC_IVAR_$_GMYTestObject$_aBooL)) = aBooL; }

static Boolean _I_GMYTestObject_aBoolean(GMYTestObject * self, SEL _cmd) { return (*(Boolean *)((char *)self + OBJC_IVAR_$_GMYTestObject$_aBoolean)); }
static void _I_GMYTestObject_setABoolean_(GMYTestObject * self, SEL _cmd, Boolean aBoolean) { (*(Boolean *)((char *)self + OBJC_IVAR_$_GMYTestObject$_aBoolean)) = aBoolean; }

static bool _I_GMYTestObject_abool(GMYTestObject * self, SEL _cmd) { return (*(bool *)((char *)self + OBJC_IVAR_$_GMYTestObject$_abool)); }
static void _I_GMYTestObject_setAbool_(GMYTestObject * self, SEL _cmd, bool abool) { (*(bool *)((char *)self + OBJC_IVAR_$_GMYTestObject$_abool)) = abool; }

static char * _I_GMYTestObject_aCharStar(GMYTestObject * self, SEL _cmd) { return (*(char **)((char *)self + OBJC_IVAR_$_GMYTestObject$_aCharStar)); }
static void _I_GMYTestObject_setACharStar_(GMYTestObject * self, SEL _cmd, char *aCharStar) { (*(char **)((char *)self + OBJC_IVAR_$_GMYTestObject$_aCharStar)) = aCharStar; }

static int * _I_GMYTestObject_aIntStar(GMYTestObject * self, SEL _cmd) { return (*(int **)((char *)self + OBJC_IVAR_$_GMYTestObject$_aIntStar)); }
static void _I_GMYTestObject_setAIntStar_(GMYTestObject * self, SEL _cmd, int *aIntStar) { (*(int **)((char *)self + OBJC_IVAR_$_GMYTestObject$_aIntStar)) = aIntStar; }

static TestEnum _I_GMYTestObject_aEnum(GMYTestObject * self, SEL _cmd) { return (*(TestEnum *)((char *)self + OBJC_IVAR_$_GMYTestObject$_aEnum)); }
static void _I_GMYTestObject_setAEnum_(GMYTestObject * self, SEL _cmd, TestEnum aEnum) { (*(TestEnum *)((char *)self + OBJC_IVAR_$_GMYTestObject$_aEnum)) = aEnum; }

static pointNode _I_GMYTestObject_aNode(GMYTestObject * self, SEL _cmd) { return (*(pointNode *)((char *)self + OBJC_IVAR_$_GMYTestObject$_aNode)); }
static void _I_GMYTestObject_setANode_(GMYTestObject * self, SEL _cmd, pointNode aNode) { (*(pointNode *)((char *)self + OBJC_IVAR_$_GMYTestObject$_aNode)) = aNode; }

static SEL _I_GMYTestObject_aSEL(GMYTestObject * self, SEL _cmd) { return (*(SEL *)((char *)self + OBJC_IVAR_$_GMYTestObject$_aSEL)); }
static void _I_GMYTestObject_setASEL_(GMYTestObject * self, SEL _cmd, SEL aSEL) { (*(SEL *)((char *)self + OBJC_IVAR_$_GMYTestObject$_aSEL)) = aSEL; }

static id _I_GMYTestObject_aId(GMYTestObject * self, SEL _cmd) { return (*(id *)((char *)self + OBJC_IVAR_$_GMYTestObject$_aId)); }
static void _I_GMYTestObject_setAId_(GMYTestObject * self, SEL _cmd, id aId) { (*(id *)((char *)self + OBJC_IVAR_$_GMYTestObject$_aId)) = aId; }

static Class _I_GMYTestObject_aClass(GMYTestObject * self, SEL _cmd) { return (*(Class *)((char *)self + OBJC_IVAR_$_GMYTestObject$_aClass)); }
static void _I_GMYTestObject_setAClass_(GMYTestObject * self, SEL _cmd, Class aClass) { (*(Class *)((char *)self + OBJC_IVAR_$_GMYTestObject$_aClass)) = aClass; }

static NSArray<NSString *> * _I_GMYTestObject_array(GMYTestObject * self, SEL _cmd) { return (*(NSArray<NSString *> **)((char *)self + OBJC_IVAR_$_GMYTestObject$_array)); }
static void _I_GMYTestObject_setArray_(GMYTestObject * self, SEL _cmd, NSArray<NSString *> *array) { (*(NSArray<NSString *> **)((char *)self + OBJC_IVAR_$_GMYTestObject$_array)) = array; }

static NSArray<CustomizeObject *> * _I_GMYTestObject_customizeArray(GMYTestObject * self, SEL _cmd) { return (*(NSArray<CustomizeObject *> **)((char *)self + OBJC_IVAR_$_GMYTestObject$_customizeArray)); }
static void _I_GMYTestObject_setCustomizeArray_(GMYTestObject * self, SEL _cmd, NSArray<CustomizeObject *> *customizeArray) { (*(NSArray<CustomizeObject *> **)((char *)self + OBJC_IVAR_$_GMYTestObject$_customizeArray)) = customizeArray; }

static NSDictionary * _I_GMYTestObject_dictionary(GMYTestObject * self, SEL _cmd) { return (*(NSDictionary **)((char *)self + OBJC_IVAR_$_GMYTestObject$_dictionary)); }
static void _I_GMYTestObject_setDictionary_(GMYTestObject * self, SEL _cmd, NSDictionary *dictionary) { (*(NSDictionary **)((char *)self + OBJC_IVAR_$_GMYTestObject$_dictionary)) = dictionary; }

static NSSet * _I_GMYTestObject_aSet(GMYTestObject * self, SEL _cmd) { return (*(NSSet **)((char *)self + OBJC_IVAR_$_GMYTestObject$_aSet)); }
static void _I_GMYTestObject_setASet_(GMYTestObject * self, SEL _cmd, NSSet *aSet) { (*(NSSet **)((char *)self + OBJC_IVAR_$_GMYTestObject$_aSet)) = aSet; }

static NSRange _I_GMYTestObject_range(GMYTestObject * self, SEL _cmd) { return (*(NSRange *)((char *)self + OBJC_IVAR_$_GMYTestObject$_range)); }
static void _I_GMYTestObject_setRange_(GMYTestObject * self, SEL _cmd, NSRange range) { (*(NSRange *)((char *)self + OBJC_IVAR_$_GMYTestObject$_range)) = range; }
// @end

我们都可以看到property 自动生成的getter和setter的实现和声明成员变量的命名符号，是不是很受冲击 - -+