1 /** 2 Instance variable information. 3 */ 4 @interface YYClassIvarInfo : NSObject 5 @property (nonatomic, assign, readonly) Ivar ivar; ///< ivar opaque struct 6 @property (nonatomic, strong, readonly) NSString *name; ///< Ivar‘s name 7 @property (nonatomic, assign, readonly) ptrdiff_t offset; ///< Ivar‘s offset 8 @property (nonatomic, strong, readonly) NSString *typeEncoding; ///< Ivar‘s type encoding 9 @property (nonatomic, assign, readonly) YYEncodingType type; ///< Ivar‘s type 10 11 /** 12 Creates and returns an ivar info object. 13 14 @param ivar ivar opaque struct 15 @return A new object, or nil if an error occurs. 16 */ 17 - (instancetype)initWithIvar:(Ivar)ivar; 18 @end
上边代码通过创建Ivar(成员变量)的 抽象类， 返回我们需要的关于Ivar 的信息，
通过一个初始化方法创建，接下来我们看看该方法的具体实现
1 - (instancetype)initWithIvar:(Ivar)ivar {
2 // 初始化判空 如果为空 就返回nil
3 if (!ivar) return nil;
4 self = [super init];
5 _ivar = ivar;
6
7 // 获取成员变量的名称
8 const char *name = ivar_getName(ivar);
9 if (name) {
10
11 // 把c的字符串转化成oc的字符串
12 _name = [NSString stringWithUTF8String:name];
13 }
14
15 _offset = ivar_getOffset(ivar);
16
17 // 获取类型编码
18 const char *typeEncoding = ivar_getTypeEncoding(ivar);
19 if (typeEncoding) {
20
21 // 转为oc的字符穿
22 _typeEncoding = [NSString stringWithUTF8String:typeEncoding];
23
24 // 转成枚举值
25 _type = YYEncodingGetType(typeEncoding);
26
27 }
28 return self;
29 }
ivar_getName
ivar_getTypeEncoding
ivar_getOffset 这三个方法都是运行时方法，分别用来获取 名称 ， 类型编码 ， 偏移量 尤其要之处的是
ivar_getOffset方法： 官方文档中的描述是这样的
1 Returns the offset of an instance variable. 2 3 Declaration 4 ptrdiff_t ivar_getOffset( Ivar ivar) 5 Discussion 6 For instance variables of type id or other object types, call object_getIvar and object_setIvar instead of using this offset to access the instance variable data directly.
ivar_getOffset函数，对于类型id或其它对象类型的实例变量，可以调用object_getIvar和object_setIvar来直接访问成员变量，而不使用偏移量。
接下来我们看看Method(方法)的 抽象类
1 /** 2 Method information. 3 */ 4 @interface YYClassMethodInfo : NSObject 5 @property (nonatomic, assign, readonly) Method method; ///< method opaque struct 6 @property (nonatomic, strong, readonly) NSString *name; ///< method name 7 @property (nonatomic, assign, readonly) SEL sel; ///< method‘s selector 8 @property (nonatomic, assign, readonly) IMP imp; ///< method‘s implementation 9 @property (nonatomic, strong, readonly) NSString *typeEncoding; ///< method‘s parameter and return types 10 @property (nonatomic, strong, readonly) NSString *returnTypeEncoding; ///< return value‘s type 11 @property (nullable, nonatomic, strong, readonly) NSArray<NSString *> *argumentTypeEncodings; ///< array of arguments‘ type 12 13 /** 14 Creates and returns a method info object. 15 16 @param method method opaque struct 17 @return A new object, or nil if an error occurs. 18 */ 19 - (instancetype)initWithMethod:(Method)method; 20 @end
这这段代码中 比较陌生的是Method 和 IMP
Method 是一个结构体:
struct objc_method
{
SEL method_name;
char * method_types;
IMP method_imp;
};
1.方法名：方法名为此方法的方法签名，相同函数名和参数的方法名是一样的2.方法类型： 描述方法的参数类型3. 方法真实实现代码块的地址指针，可像C 一样直接调用 1 - (instancetype)initWithMethod:(Method)method {
2 if (!method) return nil;
3 self = [super init];
4 _method = method;
5
6 // Method获取方法的名称
7 _sel = method_getName(method);
8
9 // 方法的实现地址
10 _imp = method_getImplementation(method);
11
12 // SEL 获取方法名
13 const char *name = sel_getName(_sel);
14 if (name) {
15 _name = [NSString stringWithUTF8String:name];
16 }
17
18 // 获取类型
19 const char *typeEncoding = method_getTypeEncoding(method);
20 if (typeEncoding) {
21 _typeEncoding = [NSString stringWithUTF8String:typeEncoding];
22 }
23
24 // 获取返回值类型
25 char *returnType = method_copyReturnType(method);
26 if (returnType) {
27 _returnTypeEncoding = [NSString stringWithUTF8String:returnType];
28
29 // 但凡 通过copy retain alloc 系统方法得到的内存，必须使用relea() 或 free() 进行释放
30 free(returnType);
31 }
32
33 // 获取参数列表
34 unsigned int argumentCount = method_getNumberOfArguments(method);
35 if (argumentCount > 0) {
36
37 NSMutableArray *argumentTypes = [NSMutableArray new];
38
39 for (unsigned int i = 0; i < argumentCount; i++) {
40
41 // 获取参数中的某一个参数
42 char *argumentType = method_copyArgumentType(method, i);
43
44 NSString *type = argumentType ? [NSString stringWithUTF8String:argumentType] : nil;
45 [argumentTypes addObject:type ? type : @""];
46 if (argumentType) free(argumentType);
47 }
48 _argumentTypeEncodings = argumentTypes;
49 }
50 return self;
51 }
上边的代码使用了运行时中 关于Method 的一些方法，再次不做介绍，但值得注意的是
但凡 通过copy retain alloc 系统方法得到的内存，必须使用relea() 或 free() 进行释放
1 /** 2 Property information. 3 */ 4 @interface YYClassPropertyInfo : NSObject 5 @property (nonatomic, assign, readonly) objc_property_t property; ///< property‘s opaque struct 6 @property (nonatomic, strong, readonly) NSString *name; ///< property‘s name 7 @property (nonatomic, assign, readonly) YYEncodingType type; ///< property‘s type 8 @property (nonatomic, strong, readonly) NSString *typeEncoding; ///< property‘s encoding value 9 @property (nonatomic, strong, readonly) NSString *ivarName; ///< property‘s ivar name 10 @property (nullable, nonatomic, assign, readonly) Class cls; ///< may be nil 11 @property (nonatomic, assign, readonly) SEL getter; ///< getter (nonnull) 12 @property (nonatomic, assign, readonly) SEL setter; ///< setter (nonnull) 13 14 /** 15 Creates and returns a property info object. 16 17 @param property property opaque struct 18 @return A new object, or nil if an error occurs. 19 */ 20 - (instancetype)initWithProperty:(objc_property_t)property;
上边的类是对属性的抽象类，让我们通过下边的代码 了解下属性编码的知识
1 objc_property_t property = class_getProperty([YYWeiboStatus class], "user");
2
3 unsigned int num;
4 objc_property_attribute_t *attr = property_copyAttributeList(property, &num);
5 for (unsigned int i = 0; i < num; i++) {
6
7 objc_property_attribute_t att = attr[i];
8 fprintf(stdout, "name = %s , value = %s \n",att.name , att.value);
9 }
10
11 const char *chars = property_getAttributes(property);
12 fprintf(stdout, "%s \n",chars);
打印的输出结果为
1 name = T , value = @"YYWeiboUser" 2 name = & , value = 3 name = N , value = 4 name = V , value = _user 5 T@"YYWeiboUser",&,N,V_user
可以看出，比较重要的是属性的编码都是以T开头 标示属性的类型 以V开头 标示属性的变量名
1 - (instancetype)initWithProperty:(objc_property_t)property {
2 if (!property) return nil;
3 self = [self init];
4
5 _property = property;
6
7 // 1. 获取属性名称
8 const char *name = property_getName(property);
9 if (name) {
10 _name = [NSString stringWithUTF8String:name];
11 }
12
13 // 2.获取每一个属性的编码字符串
14 YYEncodingType type = 0;
15 unsigned int attrCount;
16 objc_property_attribute_t *attrs = property_copyAttributeList(property, &attrCount);
17
18 // 3. 编译每一个属性的 objc_property_attribute_t
19 for (unsigned int i = 0; i < attrCount; i++) {
20
21 // 3.1 根据objc_property_attribute_t 中的name 做一些事
22 switch (attrs[i].name[0]) {
23
24 // T 代码属性的类型编码
25 case ‘T‘: { // Type encoding
26 if (attrs[i].value) {
27 _typeEncoding = [NSString stringWithUTF8String:attrs[i].value];
28 type = YYEncodingGetType(attrs[i].value);
29
30 // 计算属性的实体类型 比如:@"User"
31 if ((type & YYEncodingTypeMask) == YYEncodingTypeObject) {
32
33 size_t len = strlen(attrs[i].value); // len = 7
34 if (len > 3) {
35 char name[len - 2]; // 新建一个长度 = len - 2 的name字符数组 长度为5
36 name[len - 3] = ‘\0‘; // 设置最后一个字符为\0
37 memcpy(name, attrs[i].value + 2, len - 3); // copy USer 到name 中，
38
39 // 获取name 的真实实体类型
40 _cls = objc_getClass(name);
41 }
42 }
43 }
44 } break;
45 case ‘V‘: { // Instance variable
46 if (attrs[i].value) {
47 _ivarName = [NSString stringWithUTF8String:attrs[i].value];
48 }
49 } break;
50 case ‘R‘: {
51 type |= YYEncodingTypePropertyReadonly;
52 } break;
53 case ‘C‘: {
54 type |= YYEncodingTypePropertyCopy;
55 } break;
56 case ‘&‘: {
57 type |= YYEncodingTypePropertyRetain;
58 } break;
59 case ‘N‘: {
60 type |= YYEncodingTypePropertyNonatomic;
61 } break;
62 case ‘D‘: {
63 type |= YYEncodingTypePropertyDynamic;
64 } break;
65 case ‘W‘: {
66 type |= YYEncodingTypePropertyWeak;
67 } break;
68 case ‘G‘: { // getter 方法
69 type |= YYEncodingTypePropertyCustomGetter;
70 if (attrs[i].value) {
71 _getter = NSSelectorFromString([NSString stringWithUTF8String:attrs[i].value]);
72 }
73 } break;
74 case ‘S‘: { // setter 方法
75 type |= YYEncodingTypePropertyCustomSetter;
76 if (attrs[i].value) {
77 _setter = NSSelectorFromString([NSString stringWithUTF8String:attrs[i].value]);
78 }
79 } // break; commented for code coverage in next line
80 default: break;
81 }
82 }
83 if (attrs) {
84 free(attrs);
85 attrs = NULL;
86 }
87
88 _type = type;
89
90 // 获取setter 和 getter 方法
91 if (_name.length) {
92 if (!_getter) {
93 _getter = NSSelectorFromString(_name);
94 }
95 if (!_setter) {
96 _setter = NSSelectorFromString([NSString stringWithFormat:@"set%@%@:", [_name substringToIndex:1].uppercaseString, [_name substringFromIndex:1]]);
97 }
98 }
99 return self;
100 }
最后让我来看看打印结果
1 objc_property_t property = class_getProperty([YYWeiboStatus class], "user"); 2 3 YYClassPropertyInfo *propertyInfo = [[YYClassPropertyInfo alloc] initWithProperty:property]; 4 5 NSLog(@"%@",propertyInfo.typeEncoding);
1 2016-05-23 16:00:12.134 ModelBenchmark[12626:245778] @"YYWeiboUser"
1 typedef struct example {
2 int* aPint;
3 double aDouble;
4 char *aString;
5 int anInt;
6 BOOL isMan;
7 struct example *next;
8 } Example;
1 @property (nonatomic, assign) Example example;
1 2016-05-23 16:04:59.493 ModelBenchmark[12684:250528] {example=^id*iB^{example}}
1 objc_property_t property = class_getProperty([YYWeiboStatus class], "statusID"); 2 3 YYClassPropertyInfo *propertyInfo = [[YYClassPropertyInfo alloc] initWithProperty:property]; 4 5 NSLog(@"%@",propertyInfo.typeEncoding);
1 2016-05-23 16:06:39.747 ModelBenchmark[12696:252148] Q
到此 关于 Ivar Method Property 的抽象类已经介绍完毕，在后面的使用中 直接使用这些抽象类来进行编码的
时间： 2024-10-11 03:26:59