Using pointers to adjust global objects in objective-c
- by Rob
Ok, so I am working with two sets of data that are extremely similar, and at the same time, these data sets are both global NSMutableArrays within the object.
data_set_one = [[NSMutableArray alloc] init];
data_set_two = [[NSMutableArray alloc] init];
Two new NSMutableArrays are loaded, which need to be added to the old, existing data. These Arrays are also global.
xml_dataset_one = [[NSMutableArray alloc] init];
xml_dataset_two = [[NSMutableArray alloc] init];
To reduce code duplication (and because these data sets are so similar) I wrote a void method within the class to handle the data combination process for both Arrays:
-(void)constructData:(NSMutableArray *)data fromDownloadArray:(NSMutableArray *)down withMatchSelector:(NSString *)sel_str
Now, I have a decent understanding of object oriented programming, so I was thinking that if I were to invoke the method with the global Arrays in the data like so...
[self constructData:data_set_one fromDownloadArray:xml_dataset_one withMatchSelector:@"id"];
Then the global NSMutableArrays (data_set_one) would reflect the changes that happen to "array" within the method. Sadly, this is not the case, data_set_one doesn't reflect the changes (ex: new objects within the Array) outside of the method.
Here is a code snippet of the problem
// data_set_one is empty
// xml_dataset_one has a few objects
[constructData:(NSMutableArray *)data_set_one fromDownloadArray:(NSMutableArray *)xml_dataset_one withMatchSelector:(NSString *)@"id"];
// data_set_one should now be xml_dataset_one, but when echoed to screen, it appears to remain empty
And here is the gist of the code for the method, any help is appreciated.
-(void)constructData:(NSMutableArray *)data fromDownloadArray:(NSMutableArray *)down withMatchSelector:(NSString *)sel_str {
if ([data count] == 0) {
data = down; // set data equal to downloaded data
} else if ([down count] == 0) {
// download yields no results, do nothing
} else {
// combine the two arrays here
}
}
This project is not ARC enabled.
Thanks for the help guys!
Rob
