Question

i have 7 custom objects with the same properties, createDate and modifiedDate. can i create a method that accepts Object1 but actually takes all 7 objects?

right now, this works:

[self setCreateAndModifiedTimeWithEvent:((Object1 *) object2 
                                 WithCreateDate:[[eventsArray objectAtIndex:i] objectForKey:@"create_date"] 
                                 AndModifiedDate:[[eventsArray objectAtIndex:i] objectForKey:@"modified_date"]];

.h file

-(void) setCreateAndModifiedTimeWithEvent:(Object1 *)object 
                           WithCreateDate:(NSString *)createStamp 
                           AndModifiedDate:(NSString *)modifiedStamp;

.m file

-(void) setCreateAndModifiedTimeWithEvent:(Object1 *)object 
                           WithCreateDate:(NSString *)createStamp 
                           AndModifiedDate:(NSString *)modifiedStamp

{
    object.A = @"Hello,";
    object.B = @"World";
}

this would cut back on good chuck of lines of code.

i know you can do this sort of thing with UIView and its subclasses. say i have a

UITextField myTextField. 

i can do

((UIScrollView *)myTextField).tag = 2;

is there anything inherently bad about typecasting my objects like this or is it acceptable?

Answer 1

Like Joe said, you’d be better off with something like this:

@interface DatedObject : NSObject

@property NSDate *createDate;
@property NSDate *modifiedDate;

@end

@implementation DatedObject

@synthesize createDate;
@synthesize modifiedDate;

@end

Then have each of the 7 classes inherit from the DatedObject base class. Inheritance is a fundamental part of Object Oriented Programming, and you should learn to use it (wisely).

Then your method can be:

-(void) setCreateAndModifiedTimeWithEvent:(DatedObject *)object 
                           WithCreateDate:(NSString *)createStamp 
                           AndModifiedDate:(NSString *)modifiedStamp;

You could also do this with a protocol, but the nice thing about using a base class that the other classes inherit from is that you only have to implement this functionality in one place. If the 7 classes don’t all currently inherit from the same base class (which would end up being the superclass of DatedObject), a protocol is probably the way to go. In that case, you can declare your method like this:

-(void) setCreateAndModifiedTimeWithEvent:(id<DatedObjectProtocol>)object 
                           WithCreateDate:(NSString *)createStamp 
                           AndModifiedDate:(NSString *)modifiedStamp;

One of the big advantages to these two approaches over what you’ve posted in your question is that you get more help from the compiler in catching places where your code sends a message to an object that doesn’t respond to it.