Question

I’m trying to use the userVisibleDateTimeStringForRFC3339DateTimeString method that Apple documents here.

So first I created a separate class called jhsDateFormatter and first modified it from

- (NSString *)userVisibleDateTimeStringForRFC3339DateTimeString:(NSString *)rfc3339DateTimeString;

to
– (NSMutableString *)userVisibleDateTimeStringForRFC3339DateTimeString:(NSMutableString *)rfc3339DateTimeString :(NSString *)rfc3339DateTimeFormatString;

so I could pass in a second parameter, which would be the desired date format string.

I then imported this new class into my view controller.m:

#import "jhsDateFormatter.h"

and called the method this way:

predicateMutableString = [userVisibleDateTimeStringForRFC3339DateTimeString:dateHolderMutableString :@"yyyy'-'MM'-'dd'"];

predicateMutableString is defined in the viewController.h and synthesized in the .m.

I got a build error: use of undeclared identifier ‘userVisibleDateTimeSTringForRFC3339DateTimeString

So I commented out my modified version and used the original code and method signature in my class file:

    - (NSString *)userVisibleDateTimeStringForRFC3339DateTimeString:(NSString *)rfc3339DateTimeString;

and called it this way:

I’m not sure why the method call isn’t being accepted. I think I’ve matched up the data types.

Please let me know your ideas of what is awry.

Thanks

Answer 1

You probably want to declare your method like this:

+ (NSMutableString *)userVisibleDateTimeStringForRFC3339DateTimeString:(NSMutableString *)rfc3339DateTimeString formatString:(NSString *)rfc3339DateTimeFormatString;

(Note the + at the start, and the fact that the second argument is now named – it was blank in your code, which is valid but weird.)

Then you’d call it like this:

predicateMutableString = [jhsDateFormatter userVisibleDateTimeStringForRFC3339DateTimeString:dateHolderMutableString formatString:@"yyyy'-'MM'-'dd'"];

Where jhsDateFormatter the new class you’ve made.

In your example code, you’re not calling the method on any object, which is why the compiler is complaining.