/**
Instance variable information.
*/
@interface YYClassIvarInfo : NSObject
@property (nonatomic, assign, readonly) Ivar ivar; ///< ivar opaque struct
@property (nonatomic, strong, readonly) NSString *name; ///< Ivar's name
@property (nonatomic, assign, readonly) ptrdiff_t offset; ///< Ivar's offset
@property (nonatomic, strong, readonly) NSString *typeEncoding; ///< Ivar's type encoding
@property (nonatomic, assign, readonly) YYEncodingType type; ///< Ivar's type /**
Creates and returns an ivar info object. @param ivar ivar opaque struct
@return A new object, or nil if an error occurs.
*/
- (instancetype)initWithIvar:(Ivar)ivar;
@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
- (instancetype)initWithIvar:(Ivar)ivar {
// 初始化判空 如果为空 就返回nil
if (!ivar) return nil;
self = [super init];
_ivar = ivar;
// 获取成员变量的名称
const char *name = ivar_getName(ivar);
if (name) {
// 把c的字符串转化成oc的字符串
_name = [NSString stringWithUTF8String:name];
}
_offset = ivar_getOffset(ivar);
// 获取类型编码
const char *typeEncoding = ivar_getTypeEncoding(ivar);
if (typeEncoding) {
// 转为oc的字符穿
_typeEncoding = [NSString stringWithUTF8String:typeEncoding];
// 转成枚举值
_type = YYEncodingGetType(typeEncoding);
}
return self;
}
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
Returns the offset of an instance variable. Declaration
ptrdiff_t ivar_getOffset( Ivar ivar)
Discussion
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
/**
Method information.
*/
@interface YYClassMethodInfo : NSObject
@property (nonatomic, assign, readonly) Method method; ///< method opaque struct
@property (nonatomic, strong, readonly) NSString *name; ///< method name
@property (nonatomic, assign, readonly) SEL sel; ///< method's selector
@property (nonatomic, assign, readonly) IMP imp; ///< method's implementation
@property (nonatomic, strong, readonly) NSString *typeEncoding; ///< method's parameter and return types
@property (nonatomic, strong, readonly) NSString *returnTypeEncoding; ///< return value's type
@property (nullable, nonatomic, strong, readonly) NSArray<NSString *> *argumentTypeEncodings; ///< array of arguments' type /**
Creates and returns a method info object. @param method method opaque struct
@return A new object, or nil if an error occurs.
*/
- (instancetype)initWithMethod:(Method)method;
@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_method1.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
{
SEL method_name;
char * method_types;
IMP method_imp;
};
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
- (instancetype)initWithMethod:(Method)method {
if (!method) return nil;
self = [super init];
_method = method;
// Method获取方法的名称
_sel = method_getName(method);
// 方法的实现地址
_imp = method_getImplementation(method);
// SEL 获取方法名
const char *name = sel_getName(_sel);
if (name) {
_name = [NSString stringWithUTF8String:name];
}
// 获取类型
const char *typeEncoding = method_getTypeEncoding(method);
if (typeEncoding) {
_typeEncoding = [NSString stringWithUTF8String:typeEncoding];
}
// 获取返回值类型
char *returnType = method_copyReturnType(method);
if (returnType) {
_returnTypeEncoding = [NSString stringWithUTF8String:returnType];
// 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
free(returnType);
}
// 获取参数列表
unsigned int argumentCount = method_getNumberOfArguments(method);
if (argumentCount > ) {
NSMutableArray *argumentTypes = [NSMutableArray new];
for (unsigned int i = ; i < argumentCount; i++) {
// 获取参数中的某一个参数
char *argumentType = method_copyArgumentType(method, i);
NSString *type = argumentType ? [NSString stringWithUTF8String:argumentType] : nil;
[argumentTypes addObject:type ? type : @""];
if (argumentType) free(argumentType);
}
_argumentTypeEncodings = argumentTypes;
}
return self;
}
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
/**
Property information.
*/
@interface YYClassPropertyInfo : NSObject
@property (nonatomic, assign, readonly) objc_property_t property; ///< property's opaque struct
@property (nonatomic, strong, readonly) NSString *name; ///< property's name
@property (nonatomic, assign, readonly) YYEncodingType type; ///< property's type
@property (nonatomic, strong, readonly) NSString *typeEncoding; ///< property's encoding value
@property (nonatomic, strong, readonly) NSString *ivarName; ///< property's ivar name
@property (nullable, nonatomic, assign, readonly) Class cls; ///< may be nil
@property (nonatomic, assign, readonly) SEL getter; ///< getter (nonnull)
@property (nonatomic, assign, readonly) SEL setter; ///< setter (nonnull) /**
Creates and returns a property info object. @param property property opaque struct
@return A new object, or nil if an error occurs.
*/
- (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
objc_property_t property = class_getProperty([YYWeiboStatus class], "user");
unsigned int num;
objc_property_attribute_t *attr = property_copyAttributeList(property, &num);
for (unsigned int i = ; i < num; i++) {
objc_property_attribute_t att = attr[i];
fprintf(stdout, "name = %s , value = %s \n",att.name , att.value);
}
const char *chars = property_getAttributes(property);
fprintf(stdout, "%s \n",chars);
打印的输出结果为
name = T , value = @"YYWeiboUser"
name = & , value =
name = N , value =
name = V , value = _user
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
- (instancetype)initWithProperty:(objc_property_t)property {
if (!property) return nil;
self = [self init];
_property = property;
// 1. 获取属性名称
const char *name = property_getName(property);
if (name) {
_name = [NSString stringWithUTF8String:name];
}
// 2.获取每一个属性的编码字符串
YYEncodingType type = ;
unsigned int attrCount;
objc_property_attribute_t *attrs = property_copyAttributeList(property, &attrCount);
// 3. 编译每一个属性的 objc_property_attribute_t
for (unsigned int i = ; i < attrCount; i++) {
// 3.1 根据objc_property_attribute_t 中的name 做一些事
switch (attrs[i].name[]) {
// T 代码属性的类型编码
case 'T': { // Type encoding
if (attrs[i].value) {
_typeEncoding = [NSString stringWithUTF8String:attrs[i].value];
type = YYEncodingGetType(attrs[i].value);
// 计算属性的实体类型 比如:@"User"
if ((type & YYEncodingTypeMask) == YYEncodingTypeObject) {
size_t len = strlen(attrs[i].value); // len = 7
if (len > ) {
char name[len - ]; // 新建一个长度 = len - 2 的name字符数组 长度为5
name[len - ] = '\0'; // 设置最后一个字符为\0
memcpy(name, attrs[i].value + , len - ); // copy USer 到name 中，
// 获取name 的真实实体类型
_cls = objc_getClass(name);
}
}
}
} break;
case 'V': { // Instance variable
if (attrs[i].value) {
_ivarName = [NSString stringWithUTF8String:attrs[i].value];
}
} break;
case 'R': {
type |= YYEncodingTypePropertyReadonly;
} break;
case 'C': {
type |= YYEncodingTypePropertyCopy;
} break;
case '&': {
type |= YYEncodingTypePropertyRetain;
} break;
case 'N': {
type |= YYEncodingTypePropertyNonatomic;
} break;
case 'D': {
type |= YYEncodingTypePropertyDynamic;
} break;
case 'W': {
type |= YYEncodingTypePropertyWeak;
} break;
case 'G': { // getter 方法
type |= YYEncodingTypePropertyCustomGetter;
if (attrs[i].value) {
_getter = NSSelectorFromString([NSString stringWithUTF8String:attrs[i].value]);
}
} break;
case 'S': { // setter 方法
type |= YYEncodingTypePropertyCustomSetter;
if (attrs[i].value) {
_setter = NSSelectorFromString([NSString stringWithUTF8String:attrs[i].value]);
}
} // break; commented for code coverage in next line
default: break;
}
}
if (attrs) {
free(attrs);
attrs = NULL;
}
_type = type;
// 获取setter 和 getter 方法
if (_name.length) {
if (!_getter) {
_getter = NSSelectorFromString(_name);
}
if (!_setter) {
_setter = NSSelectorFromString([NSString stringWithFormat:@"set%@%@:", [_name substringToIndex:].uppercaseString, [_name substringFromIndex:]]);
}
}
return self;
}
最后让我来看看打印结果
objc_property_t property = class_getProperty([YYWeiboStatus class], "user");
YYClassPropertyInfo *propertyInfo = [[YYClassPropertyInfo alloc] initWithProperty:property];
NSLog(@"%@",propertyInfo.typeEncoding);
-- ::12.134 ModelBenchmark[:] @"YYWeiboUser"
typedef struct example {
int* aPint;
double aDouble;
char *aString;
int anInt;
BOOL isMan;
struct example *next;
} Example;
@property (nonatomic, assign) Example example;
-- ::59.493 ModelBenchmark[:] {example=^id*iB^{example}}
objc_property_t property = class_getProperty([YYWeiboStatus class], "statusID");
YYClassPropertyInfo *propertyInfo = [[YYClassPropertyInfo alloc] initWithProperty:property];
NSLog(@"%@",propertyInfo.typeEncoding);
-- ::39.747 ModelBenchmark[:] 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