Get an object properties list in Objective-C

I just managed to get the answer myself. By using the Obj-C Runtime Library, I had access to the properties the way I wanted:

- (void)myMethod {
    unsigned int outCount, i;
    objc_property_t *properties = class_copyPropertyList([self class], &outCount);
    for(i = 0; i < outCount; i++) {
        objc_property_t property = properties[i];
        const char *propName = property_getName(property);
        if(propName) {
            const char *propType = getPropertyType(property);
            NSString *propertyName = [NSString stringWithCString:propName
                                                                encoding:[NSString defaultCStringEncoding]];
            NSString *propertyType = [NSString stringWithCString:propType
                                                                encoding:[NSString defaultCStringEncoding]];
            ...
        }
    }
    free(properties);
}

This required me to make a 'getPropertyType' C function, which is mainly taken from an Apple code sample (can't remember right now the exact source):

static const char *getPropertyType(objc_property_t property) {
    const char *attributes = property_getAttributes(property);
    char buffer[1 + strlen(attributes)];
    strcpy(buffer, attributes);
    char *state = buffer, *attribute;
    while ((attribute = strsep(&state, ",")) != NULL) {
        if (attribute[0] == 'T') {
            if (strlen(attribute) <= 4) {
                break;
            }
            return (const char *)[[NSData dataWithBytes:(attribute + 3) length:strlen(attribute) - 4] bytes];
        }
    }
    return "@";
}

The word "attributes" is a little fuzzy. Do you mean instance variables, properties, methods that look like accessors?

The answer to all three is "yes, but it's not very easy." The Objective-C runtime API includes functions to get the ivar list, method list or property list for a class (e.g., class_copyPropertyList()), and then a corresponding function for each type to get the name of an item in the list (e.g., property_getName()).

All in all, it can be kind of a lot of work to get it right, or at least a lot more than most people would want to do for what usually amounts to a really trivial feature.

Alternatively, you could just write a Ruby/Python script that just reads a header file and looks for whatever you'd consider "attributes" for the class.

I was able to get @orange80's answer to work WITH ARC ENABLED… ... for what I wanted - at least... but not without a bit of trial and error. Hopefully this additional information may spare someone the grief.

Save those classes he describes in his answer = as a class, and in your AppDelegate.h (or whatever), put #import PropertyUtil.h. Then in your...

- (void)applicationDidFinishLaunching:
         (NSNotification *)aNotification {

method (or whatever) …

PropertyUtil *props  = [PropertyUtil new];  
NSDictionary *propsD = [PropertyUtil classPropsFor:
                          (NSObject*)[gist class]];  
NSLog(@"%@, %@", props, propsD);
…

The secret is to cast the instance variable of your class (in this Case my class is Gist, and my instance of Gist is gist) that you want to query... to NSObject… (id), etc, won't cut it.. for various, weird, esoteric reasons. This will give you some output like so…

<PropertyUtil: 0x7ff0ea92fd90>, {
apiURL = NSURL;
createdAt = NSDate;
files = NSArray;
gistDescription = NSString;
gistId = NSString;
gitPullURL = NSURL;
gitPushURL = NSURL;
htmlURL = NSURL;
isFork = c;
isPublic = c;
numberOfComments = Q;
updatedAt = NSDate;
userLogin = NSString;
}

For all of Apple's unabashed / OCD bragging about ObjC's "amazeballs" "introspection... They sure don't make it very easy to perform this simple "look" "at one's self", "so to speak"..

If you really want to go hog wild though.. check out.. class-dump, which is a mind-bogglingly insane way to peek into class headers of ANY executable, etc… It provides a VERBOSE look into your classes… that I, personally, find truly helpful - in many, many circumstances. it is actually why I i started seeking a solution to the OP's question. here are some of the usage parameters.. enjoy!

    -a             show instance variable offsets
    -A             show implementation addresses
    --arch <arch>  choose a specific architecture from a universal binary (ppc, ppc64, i386, x86_64)
    -C <regex>     only display classes matching regular expression
    -f <str>       find string in method name
    -I             sort classes, categories, and protocols by inheritance (overrides -s)
    -r             recursively expand frameworks and fixed VM shared libraries
    -s             sort classes and categories by name
    -S             sort methods by name

For Swift onlookers, you can get this functionality by utilising the Encodable functionality. I will explain how:

1. Conform your object to Encodable protocol

   class ExampleObj: NSObject, Encodable {
       var prop1: String = ""
       var prop2: String = ""
   }
   

2. Create extension for Encodable to provide toDictionary functionality

    public func toDictionary() -> [String: AnyObject]? {
       let encoder = JSONEncoder()
       encoder.outputFormatting = .prettyPrinted
       guard let data =  try? encoder.encode(self),
             let json = try? JSONSerialization.jsonObject(with: data, options: .init(rawValue: 0)), let jsonDict = json as? [String: AnyObject] else {
           return nil
       }
       return jsonDict
   }
   

3. Call toDictionary on your object instance and access keys property.

   let exampleObj = ExampleObj()
   exampleObj.toDictionary()?.keys
   

4. Voila! Access your properties like so:

   for k in exampleObj!.keys {
       print(k)
   }
   // Prints "prop1"
   // Prints "prop2"