Question

I can’t seem to get round this error; use of undeclared identifier ‘ageBy’.
I dont understand why am getting it as i have the import Person.h in my code.
Thanks for your time and any help.

Person.h

@interface Person : NSObject
{
 int _age;
 int _years;
 NSString *_name;
 NSString *_job;

} 

-(void)setAge:(int)age;
-(int)age;

-(void)setName:(NSString *)name;
-(NSString *)name;

-(void)setJob:(NSString *)job;
-(NSString *)job;

-(NSString *)summaryString;

-(void)ageBy:(int)years;


@end

Person.m

#import "Person.h"
@implementation Person

-(void)setAge:(int)age{
  _age = age;
}
-(int)age{
  return _age;
}
-(void)setName:(NSString *)name{
  _name = name;
}
-(NSString *)name{
  return _name; }

-(void)setJob:(NSString *)job{
  _job = job;
}
-(NSString *)job{
  return _job;
}

-(NSString *)summaryString{
  return [NSString stringWithFormat:@"The Person %@ is %d years old and is a  %@",_name,_age,_job];

-(void)ageBy:(int)years{
  _years = years;
  _age = years + _age;

 }

 } 
 @end

Answer 1

Your ageBy: is defined inside summaryString. You probably want to move the curly bracket just before @end so that it is above -(void)ageBy:(int)years. So:

-(NSString *)summaryString{
  return [NSString stringWithFormat:@"The Person %@ is %d years old and is a  %@",_name,_age,_job];
 } 

-(void)ageBy:(int)years{
  _years = years;
  _age = years + _age;

 }

Also as a style note, if summaryString is merely for debugging then you’d possibly be better off declaring it as description. The latter is the standard form for getting an implementation-dependand string description of an Objective-C object, with the net effect that collection objects like NSArray know to call description on all their child objects in order to create the correct output.