get or set a ivar of NSObject

gistfile1.txt

//
//  NSIvarOffset.h
//  whatshook
//
//  Created by minisj.net on 2020/11/17.
//

NS_ASSUME_NONNULL_BEGIN

@interface Objc : NSObject

+(id)getVar:(id)target atOffset:(int)offset;

+(void)setTarget:(id)target var:(id)var atOffset:(int)offset;

+(uint64_t)getVarUint64:(id)target atOffset:(int)offset;

@end

NS_ASSUME_NONNULL_END










#import "NSIvarOffset.h"

#if __has_feature(objc_arc)
#error "please turn arc off, using -fno-objc-arc"
#else
#endif



@implementation Objc

+(id)getVar:(id)target atOffset:(int)offset
{
    if (target == nil) {
        return nil;
    }
    
    void *p = (__bridge void*)target;
    p = (char*)p + offset;
    
    void **o = (void**)p;
    id aa = (__bridge id)*o;
    return aa;
}

+(uint64_t)getVarUint64:(id)target atOffset:(int)offset
{
    void *p = (__bridge void*)target;
    p = (char*)p + offset;
    
    uint64_t **o = (uint64_t**)p;
    uint64_t aa = *o;
    return aa;
}

+(void)setTarget:(id)target var:(id)var atOffset:(int)offset
{
    if (target == nil) {
        return;
    }

    [var retain];
    
    void *p = (__bridge void*)target;
    p = (char*)p + offset;
    
    uint64_t *var2 = (uint64_t*)(__bridge void*)var;
    
    ((uint64_t*)p)[0] = var2;
}
@end