How can I access this variable Globally in Objective C?

Here is the code im having issues with:

if(DriveInfoDict) {
    NSLog(@"%@", DriveInfoDict);
    //PrevSp开发者_StackOverfloweedsDict = [DriveInfoDict objectForKey: @"speed"];
    //NSLog(@"Previous Speed Dict:%@", PrevSpeedsDict);
}



DriveInfoDict = [NSDictionary dictionaryWithObjectsAndKeys:
                 [NSNumber numberWithDouble: CurrentLatitude], @"Lat",
                 [NSNumber numberWithDouble: CurrentLongitude], @"Long",
                 [NSNumber numberWithDouble:speedMPH], @"speed",
                 nil];  

Here, I would like to set DriveInfoDict, so that the next time the function runs it will have the previous value. I have stripped the operators to simplify my problem.

The error I am getting is : EXC-BAD-ACCESS

I am new to Obj-C and I do not know how to make this object accessible here. Some code with explanation as to if it goes in the H or M file would be very helpful.

You need to retain the dictionary or use alloc/init (which returns a retained dictionary. So either:

DriveInfoDict = [[NSDictionary dictionaryWithObjectsAndKeys:
                 [NSNumber numberWithDouble: CurrentLatitude], @"Lat",
                 [NSNumber numberWithDouble: CurrentLongitude], @"Long",
                 [NSNumber numberWithDouble:speedMPH], @"speed",
                 nil] retain];

or:

DriveInfoDict = [[NSDictionary alloc] initWithObjectsAndKeys:
                 [NSNumber numberWithDouble: CurrentLatitude], @"Lat",
                 [NSNumber numberWithDouble: CurrentLongitude], @"Long",
                 [NSNumber numberWithDouble:speedMPH], @"speed",
                 nil];

If you replace the content of DriveInfoDict (that is: assign a new dictionary) don't forget to first release it.