How to set all properties of an NSObject to nil without having to specify all the properties explicitly.?

Question

I have a singleton object which has some properties and I would like to set all these values to nil or "NO" based on the type of properties. One way to do it is to write a reset method in which I set all these properties to nil myself like below..

This may even have instance variables which are also to be cleared.

-(void)reset
{
    //Properties
    self.lastLoggedInUser = nil;
    self.localMasterDownload = NO;
    self.isFirstLaunchDone = NO;
    self.lastArchvingDate = nil;
    self.archivingDueDate = nil;
    self.dbEncryptionKey = nil;
    self.checkInDone = NO;
    //Instance variables
    _isPostionModuleExtandedMode = NO;
    _isPassengerModuleExtandedMode = NO;
}

But I am looking for a more generic and efficient method of doing this..

Any help is appreciated.

Thanks.

What you posted is the most efficient way. Any approach that dynamically processes the objects's properties will be far less efficient. — rmaddy, Aug 13 '14 at 07:04
@rmaddy Is there any way I can use the objective-c runtime to my use..? Say If I have a lot properties and I dont want to write so much code.. instead I want write a method in the base class instead which will clear this for me...? — Ankit Srivastava, Aug 13 '14 at 07:05
I've never done what you want but start by looking at http://stackoverflow.com/questions/11774162/list-of-class-properties-in-objective-c — rmaddy, Aug 13 '14 at 07:10
The dynamic nature of Objective-C makes this very difficult to implement. What you really need is a brute force aproach. You'd have to every possible property name from aaaaaaaaaaaaaaaaaa to zzzzzzzzzzzzzzzzzzz (that would be hundreds of trillions of possible property names) and test each one with `respondsToSelector:`. Class introspection doesn't work, because there could be additional property names that are not exposed. For example NSManagedObject gets it's properties from the `mom` file, not from anything inherent in the class. Alternatively, just manually reset everything as you're doing. — Abhi Beckert, Aug 13 '14 at 07:29
Is there some reason you can't destroy and re-allocate the instance? — jscs, Aug 13 '14 at 14:56
@JoshCaswell Initialisation of the singleton is a heavy task. — Ankit Srivastava, Aug 14 '14 at 08:17

score 1 · Answer 1 · answered Dec 21 '16 at 02:05

This gets you your classes properties, from there you just have to convert the key string into something that trys to nil the property. Its possible I think.

NSMutableDictionary *dict = [NSMutableDictionary dictionary];

unsigned count;
objc_property_t *properties = class_copyPropertyList([self class], &count);

for (int i = 0; i < count; i++) {
    NSString *key = [NSString stringWithUTF8String:property_getName(properties[i])];
    if([self valueForKey:key]!=nil){
        [dict setObject:[self valueForKey:key] forKey:key];


    }else{
        [dict setObject:@NO forKey:key];

    }
}

free(properties);

return [NSDictionary dictionaryWithDictionary:dict];

score 0 · Answer 2 · answered Feb 12 '17 at 12:49

- (void) resetProperties {
    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) {
            NSString *propertyName = [NSString stringWithCString:propName encoding:[NSString defaultCStringEncoding]];

            id value = [self valueForKey:propertyName];
            NSLog(@"[berore]XXXresetProperties => [%@] %@=%@", [propertyName class],propertyName, value);

            /* You can add some other checks */
            if ([value isKindOfClass:[NSNumber class]]) {
                [self setValue:[NSNumber numberWithInteger:0] forKeyPath:propertyName];
            }
            if ([value isKindOfClass:[NSString class]]) {
                [self setValue:nil forKeyPath:propertyName];
            }
            if ([value isKindOfClass:[NSDictionary class]]) {
                [self setValue:nil forKeyPath:propertyName];
            }

            id valueRes = [self valueForKey:propertyName];
            NSLog(@"[after]XXXresetProperties => [%@] %@=%@\n---\n", [propertyName class],propertyName, valueRes);
        }
    }
    free(properties);
}

You can get it there: https://github.com/energy6x6/iOS-clear-all-property-in-class

How to set all properties of an NSObject to nil without having to specify all the properties explicitly.?

2 Answers2