我们都知道,属性和成员变量在runtime中就是property和Ivar,研究runtime的话,理解并学会使用它们能让你灵活的操作类中的值.

Property

一个类的属性其实包含了3个我们知道的东西,分别是成员变量,setter和getter,但是我们怎么样能拿到他们呢?

首先先获取类的所有属性:

Class clazz = [self class];

unsigned int outCount = 0;

objc_property_t *propertyList = class_copyPropertyList(clazz, &outCount);

得到其一:

objc_property_t aproperty = propertyList[i];

得到属性名称和值:

NSString *pName = [NSString stringWithUTF8String:property_getName(aproperty)];

id pValue = [self valueForKey:pName];

得到属性的类型和对应的成员变量:

unsigned int attributeOutCount = 0;

objc_property_attribute_t *attributeList = property_copyAttributeList(aproperty, &attributeOutCount);

objc_property_attribute_t attribute = attributeList[i];

NSString *type; NSString *ivarName;

for (int j = 0; j<attributeOutCount; j++) {

objc_property_attribute_t attribute = attributeList[j];

NSString *atName = [NSString stringWithUTF8String:attribute.name];

NSString *atValue = [NSString stringWithUTF8String:attribute.value];

if ([atName isEqualToString:@"T"]) { type = atValue; }

if ([atName isEqualToString:@"V"]) { ivarName = atValue; }

}

简单解释一下,其中objc_property_attribute_t中有name和value,name有"T","C","N","V","&"等等一些不明的值,但通过相对应的value可以知道,"T"其实是type,即属性的类型,"V"则是成员变量名,其他几个我就不得而知了.

获取属性的setter和getter:

NSString *methodName = [NSString stringWithFormat:@"set%@%@:",[pName substringToIndex:1].uppercaseString,[pName substringFromIndex:1]];

SEL setter = sel_registerName(methodName.UTF8String);

SEL getter = sel_registerName(propertyName);

如果你想调用一下:

if ([objc respondsToSelector:setter]) {
            ((void (*)(id, SEL,id))(void *)objc_msgSend)(objc, setter,value);
}

注意:propertyList和attributeList最好free一下.

Ivar

得到所有的:

unsigned int ivarOutCount = 0;

 Ivar *ivarList = class_copyIvarList(clazz, &ivarOutCount);

//每个变量其实都是Ivar类型的结构体

Ivar ivar = ivarList[i];

//变量名称

 NSString *ivarName = [NSString stringWithUTF8String:ivar_getName(ivar)];

//变量的值

id value = [self valueForKey:ivarName];

//变量的类型

 const char *type = ivar_getTypeEncoding(ivar);