最近发现在iOS 13的系统下使用kvc获取一些控件的私有成员出现崩溃，发现是苹果在对应的控件类中重写了kvc相关方法，判断key名来禁止一些成员的获取，心血来潮之下就自己实现了一个kvc。
实现思路
-(id)valueForKey:(NSString *)key方法的实现
系统的方法中针对NSArray和NSSet集合类也做了处理，我这里去掉了这部分逻辑。大致查找过程如下：
假设传入的key名称为name
- 首先查看是否有getName, name, isName, _name方法，如果有直接通过对应的方法获取返回值，如果返回值是标量类型(int,float等)，包装成NSNumber或者NSValue类型；如果没找到方法跳到第2步。
- 判断是否开启accessInstanceVariablesDirectly，如果为YES，进入第3步；否则进入第4步
- 查找是否有_name, _isName, name, isName 成员变量，如果有则通过对象的地址+成员变量的偏移量获取对应的数据，同样将标量类型进行包装；如果没有找到成员变量进入第三步。
- 调用valueForUndefinedKey:来抛出异常。
首先是获取对应方法的IMP指针，然后通过NSMethodSignature获取方法签名，这样就拿到了返回值类型，对于int,float标量类型就包装成NSNumber返回，结构体包装成NSValue返回。如果没有对应的getter方法，则获取对应类的ivarList，拿到typeEncoding和偏移量，通过偏移量获取成员变量的地址，并根据typeEncoding解析数据类型取值，同样非对象类型包装成对应的Obejct返回。
- (void)setValue:(id)value forKey:(NSString *)key方法的实现
同样假设传入的key名称为name
- 首先查看是否有setName: , _setName: 方法，如果有直接通过对应的方法赋值，如果成员变量是标量类型(int,float等)，则将传入的参数value解包成对应类型数据；如果没找到方法跳到第2步。
- 判断是否开启accessInstanceVariablesDirectly，如果为YES，进入第3步；否则进入第4步
- 查找是否有_name, _isName, name, isName成员变量，如果有则通过对象的地址+成员变量的偏移量获取成员变量的地址，同样将参数value解包成对应数据类型；如果没有找到成员变量进入第4步。
- 调用setValue:forUndefinedKey:来抛出异常
首先获取对应的setter方法的IMP指针，然后通过NSMethodSignature获取方法签名，获取setter方法参数的类型，对于参数是结构体类型通过NSGetSizeAndAlignment方法获取类型size，然后构建buffer，将value当成NSValue类型填充buffer数据，然后通过NSInvocation调用setter方法。如果没有对应的setter方法，则获取对应类的ivarList，拿到typeEncoding和偏移量，通过偏移量获取成员变量的地址并转换成对应类型的指针，然后将value解包成对应类型赋值。
另外，系统的kvc中不支持 long double,char *, void *, union, c数组等类型，所以在我的实现中也跟系统保持一致，判断出是该类型直接抛出异常。
代码如下所示，也可以直接去git下载查看
+ (BOOL)jk_accessInstanceVariablesDirectly {
return YES;
}
/** valueForKey查找过程：假设传入的key为@"name"
1、首先查看是否有getName,name,isName,_name方法，如果有直接通过对应的方法获取返回值，如果返回值是标量类型(int,float等)，包装成NSNumber或者NSValue类型；如果没找到方法跳到第2步。
2、判断是否开启jk_accessInstanceVariablesDirectly，如果为YES，进入第3步；否则进入第4步
3、查找是否有_name,_isName,name,isName 成员变量，如果有则通过对象的地址+成员变量的偏移量获取对应的数据，同样将标量类型进行包装；如果没有找到成员变量进入第三步。
4、调用valueForUndefinedKey:来抛出异常。
*/
- (id)jk_valueForKey:(NSString *)key {
if (!key || key.length <= 0) {
[self valueForUndefinedKey:key];
}
NSString *upperFirsetCharKey = [NSString stringWithFormat:@"%@%@",[[key substringWithRange:NSMakeRange(0, 1)] uppercaseString], [key substringWithRange:NSMakeRange(1, key.length - 1)]];
id obj;
#define PerformGetterMethod(m) obj = _toggleGetterMethod(self, m, key);\
if (obj) {\
return obj;\
}
// getMethod = get;
NSString *getMethod = [NSString stringWithFormat:@"get%@",upperFirsetCharKey];
PerformGetterMethod(getMethod);
// getMethod = key
getMethod = key;
PerformGetterMethod(getMethod);
// getMethod = is
getMethod = [NSString stringWithFormat:@"is%@",upperFirsetCharKey];
PerformGetterMethod(getMethod);
// getMethod = _
getMethod = [NSString stringWithFormat:@"_%@",key];
PerformGetterMethod(getMethod);
//仿照系统的KVC中，会判断accessInstanceVariablesDirectly
Class cls = [self class];
if ([cls jk_accessInstanceVariablesDirectly] == NO) {
[self valueForUndefinedKey:key];
}
return _getValFromVariable(self, key);
}
/** setValue:ForKey:过程：假设传入的key为@"name"
1、首先查看是否有setName:,_setName:方法，如果有直接通过对应的方法赋值，如果成员变量是标量类型(int,float等)，则将传入的参数value解包成对应类型数据；如果没找到方法跳到第2步。
2、判断是否开启jk_accessInstanceVariablesDirectly，如果为YES，进入第3步；否则进入第4步
3、查找是否有_name,_isName,name,isName成员变量，如果有则通过对象的地址+成员变量的偏移量获取成员变量的地址，同样将参数value解包成对应数据类型；如果没有找到成员变量进入第4步。
4、调用setValue:forUndefinedKey:来抛出异常。
*/
- (void)jk_setValue:(id)value forKey:(NSString *)key {
if (!key || key.length <= 0) {
[self setValue:value forUndefinedKey:key];
}
NSString *upperFirsetCharKey = [NSString stringWithFormat:@"%@%@",[[key substringWithRange:NSMakeRange(0, 1)] uppercaseString], [key substringWithRange:NSMakeRange(1, key.length - 1)]];
//setterMethod = set:
NSString *setterMethod = [NSString stringWithFormat:@"set%@:",upperFirsetCharKey];
if(_toggleSetterMethod(self, setterMethod, key, value)) {
return;
}
//setterMethod = _set:
setterMethod = [NSString stringWithFormat:@"_set%@:",upperFirsetCharKey];
if (_toggleSetterMethod(self, setterMethod, key, value)) {
return;
}
//仿照系统的KVC中，会判断accessInstanceVariablesDirectly
Class cls = [self class];
if ([cls accessInstanceVariablesDirectly] == NO) {
[self setValue:value forUndefinedKey:key];
}
if(_setValForVariable(self, key, value) == NO) {
[self setValue:value forUndefinedKey:key];
}
}
- (id)jk_valueForKeyPath:(NSString *)keyPath {
NSArray *array = [keyPath componentsSeparatedByString:@"."];
if (array.count <= 0) {
[self valueForUndefinedKey:keyPath];
}
id obj = self;
for (int i = 0; i < array.count; i++) {
NSString *key = array[i];
obj = [obj jk_valueForKey:key];
}
return obj;
}
- (void)jk_setValue:(id)value forKeyPath:(NSString *)keyPath {
NSArray *array = [keyPath componentsSeparatedByString:@"."];
if (array.count <= 0) {
[self setValue:value forUndefinedKey:keyPath];
}
id obj = self;
for (int i = 0; i < array.count; i++) {
NSString *key = array[i];
if (i < array.count - 1) {
obj = [obj jk_valueForKey:key];
} else {
[obj jk_setValue:value forKey:key];
}
}
}
#pragma mark - AssociatedObject
- (_TrunkObject *)trunk {
_TrunkObject *obj = objc_getAssociatedObject(self, _cmd);
if (obj == nil) {
obj = [_TrunkObject new];
objc_setAssociatedObject(self, _cmd, obj, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
}
return obj;
}
#pragma mark - pravite method
id _toggleGetterMethod(id self, NSString *methodName, NSString *key) {
SEL selector = NSSelectorFromString(methodName);
if ([self respondsToSelector:selector]) {
NSMethodSignature *sign = [self methodSignatureForSelector:selector];
const char *returnType = sign.methodReturnType;
char type = returnType[0];
IMP imp = [self methodForSelector:selector];
switch (type) {
case 'B': { //BOOL
return @(((BOOL(*)(id,SEL))imp)(self,selector));
break;
};
case 'c': { //char
return @(((char(*)(id,SEL))imp)(self,selector));
break;
};
case 'C': { //unsigned char
return @(((unsigned char(*)(id,SEL))imp)(self,selector));
break;
};
case 's': { //short
return @(((short(*)(id,SEL))imp)(self,selector));
break;
};
case 'S': { //unsigned short
return @(((unsigned short(*)(id,SEL))imp)(self,selector));
break;
};
case 'i': { //int
return @(((int(*)(id,SEL))imp)(self,selector));
break;
};
case 'I': { //unsigned int
return @(((unsigned int(*)(id,SEL))imp)(self,selector));
break;
};
case 'l': { //long
return @(((long(*)(id,SEL))imp)(self,selector));
break;
};
case 'L': { //unsigned long
return @(((unsigned long(*)(id,SEL))imp)(self,selector));
break;
};
case 'q': { //long long
return @(((long long(*)(id,SEL))imp)(self,selector));
break;
};
case 'Q': { //unsigned long long
return @(((unsigned long long(*)(id,SEL))imp)(self,selector));
break;
};
case 'f': { //float
return @(((float(*)(id,SEL))imp)(self,selector));
break;
};
case 'd': { //double
return @(((double(*)(id,SEL))imp)(self,selector));
break;
};
case 'D': { //long double
//系统的kvc中不支持long double类型
[self valueForUndefinedKey:key];
break;
}
case '@': { //id
return ((id(*)(id,SEL))imp)(self,selector);
break;
};
case '#': { //Class
return ((Class(*)(id,SEL))imp)(self,selector);
break;
};
case '*': { // char *
//系统的kvc不支持char*
[self valueForUndefinedKey:key];
break;
}
case '^':{ //pointer
//系统的kvc不支持pointer
[self valueForUndefinedKey:key];
break;
}
case '{': { //结构体
NSUInteger size = 0;
NSGetSizeAndAlignment(returnType, &size, nil);
Byte buffer[size];
//系统KVC内部也是用NSInvocation调用get方法取值
NSInvocation *invocation = [NSInvocation invocationWithMethodSignature:sign];
invocation.target = self;
invocation.selector = selector;
[invocation invoke];
[invocation getReturnValue:buffer];
return [NSValue valueWithBytes:buffer objCType:returnType];
break;
};
case '(': { //联合体
//系统的kvc不支持联合体
[self valueForUndefinedKey:key];
break;
};
case '[': {// c数组
//系统的kvc中不支持c数组
[self valueForUndefinedKey:key];
break;
}
default: { // unknown
[self valueForUndefinedKey:key];
break;
};
}
}
return nil;
}
id _getValFromVariable(NSObject *self, NSString *key) {
//首字母大写
NSString *upperFirsetCharKey = [NSString stringWithFormat:@"%@%@",[[key substringWithRange:NSMakeRange(0, 1)] uppercaseString], [key substringWithRange:NSMakeRange(1, key.length - 1)]];
unsigned int count = self.trunk.count;
Ivar *ivarList = self.trunk.ivarList;
if(ivarList == nil) {
ivarList = class_copyIvarList([self class], &count);
self.trunk.ivarList = ivarList;
self.trunk.count = count;
}
NSString *_key = [NSString stringWithFormat:@"_%@", key];
NSString *isKey = [NSString stringWithFormat:@"is%@", upperFirsetCharKey];
NSString *_isKey = [NSString stringWithFormat:@"_%@", isKey];
Ivar foundedIvar = nil;
for (int i = 0; i < count; i++) {
Ivar ivar = ivarList[i];
NSString *ivarName = @(ivar_getName(ivar));
if ([ivarName isEqualToString:_key] || [ivarName isEqualToString:_isKey] || [ivarName isEqualToString:key] || [ivarName isEqualToString:isKey]) {
foundedIvar = ivar;
break;
}
}
if (foundedIvar) {
uintptr_t offset = ivar_getOffset(foundedIvar);
const char *typeEncoding = ivar_getTypeEncoding(foundedIvar);
char type = typeEncoding[0];
void *ivarPtr = (__bridge void *)self + offset;
switch (type) {
case 'B': { //BOOL
BOOL *val = (BOOL *)ivarPtr;
return @(*val);
break;
};
case 'c': { //char
char *val = (char *)ivarPtr;
return @(*val);
break;
};
case 'C': { //unsigned char
unsigned char *val = (unsigned char *)ivarPtr;
return @(*val);
break;
};
case 's': { //short
short *val = (short *)ivarPtr;
return @(*val);
break;
};
case 'S': { //unsigned short
unsigned short *val = (unsigned short *)ivarPtr;
return @(*val);
break;
};
case 'i': { //int
int *val = (int *)ivarPtr;
return @(*val);
break;
};
case 'I': { //unsigned int
unsigned int *val = ivarPtr;
return @(*val);
break;
};
case 'l': { //long
long *val = (long *)ivarPtr;
return @(*val);
break;
};
case 'L': { //unsigned long
unsigned long *val = (unsigned long *)ivarPtr;
return @(*val);
break;
};
case 'q': { //long long
long long *val = (long long *)ivarPtr;
return @(*val);
break;
};
case 'Q': { //unsigned long long
unsigned long long *val = (unsigned long long *)ivarPtr;
return @(*val);
break;
};
case 'f': { //float
float *val = (float *)ivarPtr;
return @(*val);
break;
};
case 'd': { //double
double *val = (double *)ivarPtr;
return @(*val);
break;
};
case 'D': { //long double
//系统的kvc中不支持long double类型
[self valueForUndefinedKey:key];
break;
}
case '@': { //id
__strong id *val = (__strong id *)ivarPtr;
return *val;
break;
};
case '#': { //Class
__strong Class *val = (__strong Class *)ivarPtr;
return *val;
break;
};
case '*': { // char *
//系统的kvc中不支持char *
[self valueForUndefinedKey:key];
break;
}
case '^':{ //pointer
//系统的kvc中不支持pointer
[self valueForUndefinedKey:key];
break;
}
case '{': { //结构体
NSUInteger size = 0;
NSGetSizeAndAlignment(typeEncoding, &size, nil);
Byte buffer[size];
memcpy(buffer, ivarPtr, size);
return [NSValue valueWithBytes:buffer objCType:typeEncoding];
break;
};
case '(': { //联合体
//系统的kvc中不支持结构体
[self valueForUndefinedKey:key];
break;
};
case '[': {// c数组
//系统的kvc中不支持long double类型
[self valueForUndefinedKey:key];
break;
}
default: { // unknown
[self valueForUndefinedKey:key];
break;
};
}
}
return nil;
}
BOOL _toggleSetterMethod(id self, NSString *methodName, NSString *key, id value) {
SEL selector = NSSelectorFromString(methodName);
if ([self respondsToSelector:selector]) {
NSMethodSignature *sign = [self methodSignatureForSelector:selector];
const char *paramType = [sign getArgumentTypeAtIndex:2];//获取参数类型
char type = paramType[0];
IMP imp = [self methodForSelector:selector];
switch (type) {
case 'B': { //BOOL
((void(*)(id,SEL,BOOL))imp)(self, selector, [value boolValue]);
return YES;
break;
};
case 'c': { //char
((void(*)(id,SEL,char))imp)(self, selector, [value charValue]);
return YES;
break;
};
case 'C': { //unsigned char
((void(*)(id,SEL,unsigned char))imp)(self, selector, [value unsignedCharValue]);
return YES;
break;
};
case 's': { //short
((void(*)(id,SEL,short))imp)(self, selector, [value shortValue]);
return YES;
break;
};
case 'S': { //unsigned short
((void(*)(id,SEL,unsigned short))imp)(self, selector, [value unsignedShortValue]);
return YES;
break;
};
case 'i': { //int
((void(*)(id,SEL,int))imp)(self, selector, [value intValue]);
return YES;
break;
};
case 'I': { //unsigned int
((void(*)(id,SEL,unsigned int))imp)(self, selector, [value unsignedIntValue]);
return YES;
break;
};
case 'l': { //long
((void(*)(id,SEL,long))imp)(self, selector, [value longValue]);
return YES;
break;
};
case 'L': { //unsigned long
((void(*)(id,SEL,unsigned long))imp)(self, selector, [value unsignedLongValue]);
return YES;
break;
};
case 'q': { //long long
((void(*)(id,SEL,long long))imp)(self, selector, [value longLongValue]);
return YES;
break;
};
case 'Q': { //unsigned long long
((void(*)(id,SEL,unsigned long long))imp)(self, selector, [value unsignedLongLongValue]);
return YES;
break;
};
case 'f': { //float
((void(*)(id,SEL,float))imp)(self, selector, [value floatValue]);
return YES;
break;
};
case 'd': { //double
((void(*)(id,SEL,double))imp)(self, selector, [value doubleValue]);
return YES;
break;
};
case 'D': { //long double
//系统的kvc中不支持long double类型
[self setValue:value forUndefinedKey:key];
break;
}
case '@': { //id
((void(*)(id,SEL,id))imp)(self, selector, value);
return YES;
break;
};
case '#': { //Class
((void(*)(id,SEL,Class))imp)(self, selector, value);
return YES;
break;
};
case '*': { // char *
//系统的kvc不支持char*
[self setValue:value forUndefinedKey:key];
break;
}
case '^':{ //pointer
//系统的kvc不支持pointer
[self setValue:value forUndefinedKey:key];
break;
}
case '{': { //结构体
if ([value isKindOfClass:[NSValue class]] == NO) {
NSException *exception = [NSException exceptionWithName:@"value类型错误" reason:@"对结构体类型使用jk_setValue:forKey:方法，请确保传入的value类型是NSValue" userInfo:nil];
[exception raise];
}
//系统KVC内部也是用NSInvocation调用set方法设值
const char * objcType= [(NSValue *)value objCType];
NSUInteger size = 0;
NSGetSizeAndAlignment(objcType, &size, nil);
Byte buffer[size];
[(NSValue *)value getValue:buffer];
NSInvocation *invocation = [NSInvocation invocationWithMethodSignature:sign];
invocation.target = self;
invocation.selector = selector;
[invocation setArgument:buffer atIndex:2];
[invocation invoke];
return YES;
break;
};
case '(': { //联合体
//系统的kvc不支持联合体
[self setValue:value forUndefinedKey:key];
break;
};
case '[': {// c数组
//系统的kvc中不支持c数组
[self setValue:value forUndefinedKey:key];
break;
}
default: { // unknown
[self setValue:value forUndefinedKey:key];
break;
};
}
}
return NO;
}
BOOL _setValForVariable(NSObject *self, NSString *key, id value) {
NSString *upperFirsetCharKey = [NSString stringWithFormat:@"%@%@",[[key substringWithRange:NSMakeRange(0, 1)] uppercaseString], [key substringWithRange:NSMakeRange(1, key.length - 1)]];
unsigned int count = self.trunk.count;
Ivar *ivarList = self.trunk.ivarList;
if(ivarList == nil) {
ivarList = class_copyIvarList([self class], &count);
self.trunk.ivarList = ivarList;
self.trunk.count = count;
}
NSString *_key = [NSString stringWithFormat:@"_%@", key];
NSString *isKey = [NSString stringWithFormat:@"is%@", upperFirsetCharKey];
NSString *_isKey = [NSString stringWithFormat:@"_%@", isKey];
Ivar foundedIvar = nil;
for (int i = 0; i < count; i++) {
Ivar ivar = ivarList[i];
NSString *ivarName = @(ivar_getName(ivar));
if ([ivarName isEqualToString:_key] || [ivarName isEqualToString:_isKey] || [ivarName isEqualToString:key] || [ivarName isEqualToString:isKey]) {
foundedIvar = ivar;
break;
}
}
if (foundedIvar) {
uintptr_t offset = ivar_getOffset(foundedIvar);
const char *typeEncoding = ivar_getTypeEncoding(foundedIvar);
char type = typeEncoding[0];
void *ivarPtr = (__bridge void *)self + offset;
switch (type) {
case 'B': { //BOOL
BOOL *val = (BOOL *)ivarPtr;
*val = [value boolValue];
return YES;
break;
};
case 'c': { //char
char *val = (char *)ivarPtr;
*val = [value charValue];
return YES;
break;
};
case 'C': { //unsigned char
unsigned char *val = (unsigned char *)ivarPtr;
*val = [value unsignedCharValue];
return YES;
break;
};
case 's': { //short
short *val = (short *)ivarPtr;
*val = [value shortValue];
return YES;
break;
};
case 'S': { //unsigned short
unsigned short *val = (unsigned short *)ivarPtr;
*val = [value unsignedShortValue];
return YES;
break;
};
case 'i': { //int
int *val = (int *)ivarPtr;
*val = [value intValue];
return YES;
break;
};
case 'I': { //unsigned int
unsigned int *val = ivarPtr;
*val = [value unsignedIntValue];
return YES;
break;
};
case 'l': { //long
long *val = (long *)ivarPtr;
*val = [value longValue];
return YES;
break;
};
case 'L': { //unsigned long
unsigned long *val = (unsigned long *)ivarPtr;
*val = [value unsignedLongValue];
return YES;
break;
};
case 'q': { //long long
long long *val = (long long *)ivarPtr;
*val = [value longLongValue];
return YES;
break;
};
case 'Q': { //unsigned long long
unsigned long long *val = (unsigned long long *)ivarPtr;
*val = [value unsignedLongLongValue];
return YES;
break;
};
case 'f': { //float
float *val = (float *)ivarPtr;
*val = [value floatValue];
return YES;
break;
};
case 'd': { //double
double *val = (double *)ivarPtr;
*val = [value doubleValue];
return YES;
break;
};
case 'D': { //long double
//系统的kvc中不支持long double类型
break;
}
case '@': { //id
__strong id *val = (__strong id *)ivarPtr;
*val = value;
return YES;
break;
};
case '#': { //Class
__strong Class *val = (__strong Class *)ivarPtr;
*val = value;
return YES;
break;
};
case '*': { // char *
//系统的kvc中不支持char *
break;
}
case '^':{ //pointer
//系统的kvc中不支持pointer
break;
}
case '{': { //结构体
if ([value isKindOfClass:[NSValue class]] == NO) {
NSException *exception = [NSException exceptionWithName:@"value类型错误" reason:@"对结构体类型使用jk_setValue:forKey:方法，请确保传入的value类型是NSValue" userInfo:nil];
[exception raise];
}
NSUInteger size = 0;
NSGetSizeAndAlignment(typeEncoding, &size, nil);
Byte buffer[size];
[(NSValue *)value getValue:buffer];
memcpy(ivarPtr, buffer, size);
return YES;
break;
};
case '(': { //联合体
//系统的kvc中不支持结构体
break;
};
case '[': {// c数组
//系统的kvc中不支持long double类型
break;
}
default: { // unknown
break;
};
}
}
return NO;
}