How to override the description method for an object and print it out?

Question

I need to override the description method to return the internal state of the object (in other words, dump all the values into a single line of text).

In my Model(Class) I have

Homework.h

#import <Foundation/Foundation.h>

@interface Homework : NSObject

@property (nonatomic, strong) NSString *className;
@property (nonatomic, strong) NSString *assignmentTitle;

@end

Homework.m

-(NSString *)description
{
return [NSString stringWithFormat:@" %@, %@", self.className, self.assignmentTitle];
}

I created an object in my ViewController

@property (nonatomic, strong) Homework *homeworkAssignment;

And I try to print it like this

  NSLog(self.homeworkAssignment.description);

But it doesn't seem to work, the output prints out a comma ",". Am I formatting the NSLog wrong? Did I override the method correctly? This is my first app (besides "Hello World").

Answer 1

The code all appears correct with regard to the implementation of description and the logging. Since the output only shows a comma it means that your two property both contain empty strings. If they were nil the string format would display them as (null).

There is a difference between a nil pointer and a reference to the empty string (@"").

Answer 2

Your code works fine, you can even just NSLog like this :

NSLog(@"%@", self.homeworkAssignment);

which returns

2013-09-29 23:56:50.375 test[2769:a0b] (null), (null)

Try assigning values to your className and assignmentTitle, so it wont return null :)