Get an object properties list in Objective-C

113

How can I get a list (in the form of an NSArray or NSDictionary) of a given object properties in Objective-C?

Imagine the following scenario: I have defined a parent class which just extends NSObject, that holds an NSString, a BOOL and an NSData object as properties. Then I have several classes which extend this parent class, adding a lot of different properties each.

Is there any way I could implement an instance method on the parent class that goes through the whole object and returns, say, an NSArray of each of the (child) class properties as NSStrings that are not on the parent class, so I can later use these NSString for KVC?

Edit Report

@orange80's answer has one problem: It actually doesn't always terminate the string with 0s. This can lead to unexpected results like crashing while trying to convert it to UTF8 (I actually had a pretty annoying crashbug just because of that. Was fun debugging it ^^). I fixed it by actually getting an NSString from the attribute and then calling cStringUsingEncoding:. This works like a charm now. (Also works with ARC, at least for me)

So this is my version of the code now:

// PropertyUtil.h
#import 

@interface PropertyUtil : NSObject

+ (NSDictionary *)classPropsFor:(Class)klass;

@end


// PropertyUtil.m
#import "PropertyUtil.h"
#import <objc/runtime.h>

@implementation PropertyUtil

static const char *getPropertyType(objc_property_t property) {
    const char *attributes = property_getAttributes(property);
    //printf("attributes=%s\n", attributes);
    char buffer[1 + strlen(attributes)];
    strcpy(buffer, attributes);
    char *state = buffer, *attribute;
    while ((attribute = strsep(&state, ",")) != NULL) {
        if (attribute[0] == 'T' && attribute[1] != '@') {
            // it's a C primitive type:
            /*
             if you want a list of what will be returned for these primitives, search online for
             "objective-c" "Property Attribute Description Examples"
             apple docs list plenty of examples of what you get for int "i", long "l", unsigned "I", struct, etc.
             */
            NSString *name = [[NSString alloc] initWithBytes:attribute + 1 length:strlen(attribute) - 1 encoding:NSASCIIStringEncoding];
            return (const char *)[name cStringUsingEncoding:NSASCIIStringEncoding];
        }
        else if (attribute[0] == 'T' && attribute[1] == '@' && strlen(attribute) == 2) {
            // it's an ObjC id type:
            return "id";
        }
        else if (attribute[0] == 'T' && attribute[1] == '@') {
            // it's another ObjC o


                        
                        
                            answered 2012-10-21T17:03:50.727

Get an object properties list in Objective-C

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