I recently came across a piece of obj-C code that looked something like this:-
#import "LocationSeeker.h"
@interface LocationSeeker ()
@end
NSString *const LocationSeekerMapTypePrefKey= @"LocationSeekerMapTypePrefKey";
NSString *const CenterCoordinateLatitudePrefKey= @"CenterCoordinateLatitudePrefKey";
NSString *const CenterCoordinateLongitudePrefKey= @"CenterCoordinateLongitudePrefKey";
@implementation LocationSeeker
+(void)initialize{//used for making factory settings
NSLog(@"initializing custom factory settings");
//THE factory settings are not saved to disk.. These effect at runtime..
NSMutableDictionary *defaults= [NSMutableDictionary dictionary];
//Setting the default as Hybrid view for map
......
}
-(IBAction)buttonDidGetPressed:(id)sender{
NSLog(@"%@",NSStringFromSelector(_cmd));
NSLog(@"%@",sender);
[[NSUserDefaults standardUserDefaults] setInteger:[sender selectedSegmentIndex] forKey:WhereamiMapTypePrefKey];
if([sender selectedSegmentIndex]==0){
[worldView setMapType:MKMapTypeStandard];
}........
.....
}In the code above, there are 3 constants declared at a global level. What i wanted to inquire was whether this is the correct place to declare and define globals. Shouldn't these be declared and defined inside @implementation LocationSeeker ? Like this:
#import "LocationSeeker.h"
@interface LocationSeeker ()
@end
@implementation LocationSeeker
NSString *const LocationSeekerMapTypePrefKey= @"LocationSeekerMapTypePrefKey";
NSString *const CenterCoordinateLatitudePrefKey= @"CenterCoordinateLatitudePrefKey";
NSString *const CenterCoordinateLongitudePrefKey= @"CenterCoordinateLongitudePrefKey";
+(void)initialize{//used for making factory settings
NSLog(@"initializing custom factory settings");
//THE factory settings are not saved to disk.. These effect at runtime..
NSMutableDictionary *defaults= [NSMutableDictionary dictionary];
//Setting the default as Hybrid view for map
......
}What are the effects of the difference between the 2 approaches?
It doesn’t matter where the globals are declared in this case.
Global variables are a C construct, not Obj-C specifically. That means their semantics don’t depend on the class structure. In other languages, the fact that the declaration was inside a class would make it part of the class, but that’s not true of C globals.
There is one exception to this. If you declare a static variable at file scope (so it’s like a global but isn’t doesn have external linkage), and if it’s declared inside an @implementation block, then it’s private to the class. Code outside the @implementation block in the same file can’t reference the static variable. If it’s declared outside the @implementation block, it’s available to all code in the same file.
But that’s a hack for static in Obj-C. In general, C rules apply.
