CODEWITHSUNDEEP
ioscore-dataentity
PruitIgoe
PruitIgoe

Reputation: 6384

Getting property values from Core Data entity

I have a viewcontroller which displays Core Data entities in a UIPicker. Select a row and that entity is passed (as a property) to another viewcontroller for displaying.

I have a method that returns all the property names of the Player entity:

- (NSArray *)allPropertyNames {

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

    NSMutableArray *rv = [NSMutableArray array];

    unsigned i;
    for (i = 0; i < count; i++)
    {
        objc_property_t property = properties[i];
        NSString *name = [NSString stringWithUTF8String:property_getName(property)];
        [rv addObject:name];
    }

    free(properties);

    return rv;
}

and then I was trying to display the values of those properties this way:

for(NSString* strThisField in arrFields) {

            UILabel* lblThisField = [[UILabel alloc] initWithFrame:CGRectMake(0.0, fieldY, vPlayerBox.frame.size.width, 30.0)];

            lblThisField.text = [Player valueForKeyPath:strThisField];

            lblThisField.textColor = AO_Brown;
            lblThisField.font = AO_SansSerif_Font;
            [vPlayerBox addSubview:lblThisField];

            fieldY = fieldY + 35.0;
        }

But I am crashing on the valueForKeyPath line so obviously I am doing something wrong. Is there a way to get property values this way or am I going down a dead end?

Thanks

Edit:

I had an error in my UILabel.text property - should of read lblThisField.text = [self.myPlayer getValueForKey:strThisKey]; but even changing that it would still crash. I wrote a second method to get the values and keys into a dictionary and though it works it seems like a clunky solution. 

- (NSDictionary*) getKeyValuesOfEntity : (Player*) thisEntity {

    NSArray* arrProperties = [self getProperties];

    NSMutableDictionary* dictKeysAndValues = [[NSMutableDictionary alloc] init];

    for(NSString* strThisKey in arrProperties) {

        id value = [thisEntity valueForKey:strThisKey];

        if ([value isKindOfClass:[NSString class]]) {

            NSString* strValue = (NSString*)value;
            [dictKeysAndValues setObject:strValue forKey:strThisKey];

        } else if ([value isKindOfClass:[NSDate class]]) {

            NSDate* dtValue = (NSDate*)value;
            [dictKeysAndValues setObject:dtValue forKey:strThisKey];

        } else if ([value isKindOfClass:[NSNumber class]]) {

            NSNumber* numValue = (NSNumber*)value;
            [dictKeysAndValues setObject:numValue forKey:strThisKey];

        } else if ([value isKindOfClass:[NSSet class]]) {

            NSSet* setValue = (NSSet*)value;
            [dictKeysAndValues setObject:setValue forKey:strThisKey];

        }
    }

    return dictKeysAndValues;

}



- (NSArray *)getProperties  {

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

    NSMutableArray *rv = [NSMutableArray array];

    unsigned i;
    for (i = 0; i < count; i++)
    {
        objc_property_t property = properties[i];
        NSString *name = [NSString stringWithUTF8String:property_getName(property)];
        [rv addObject:name];
    }

    free(properties);

    return rv;
}

Upvotes: 0

Views: 98

Answers (1)

wzso
wzso

Reputation: 3885

I don't know "Player" in your for-in loop stands for a class or an instance. The method -[NSObject valueForKeypath] is an instance method. So you need to initialize an instance of class Player by doing this:

Player *player = [NSEntityDescription insertNewObjectForEntityForName:@"Player" inManagedObjectContext:appDelegate.managedObjectContext];

And everything will go cool. Hope this will help.

Upvotes: 1

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