Question

Can someone walk me through how to ‘hide’ the standard core data setters?

I know there is not really a way to define ‘Private’ methods in Objective-C, but read about using an extension to achieve a similar result. The problem is, I want to apply this to core data classes. I would like to hide the standard setters created for some attributes, and only call them from inside other, exposed setters.

An example: My core data object has a BOOL ‘collected’ and a date ‘dateCollected’. I have figured out how to add setDateCollected to setCollected, but now I would like to ‘hide’ set collected so that it can’t be called directly so easily (when I might forget to also set dateCollected manually).

To clarify, the part that is tripping me up is the ‘@dynamic’ calls – I don;t know where these should live.

EDIT – I guess I missed a part. I can move the @property declaration into the implementation file just fine. But I want the setter to be hidden, and the getter to remain public. I guess I need to replace the @property, but I don’t know how to do this for a core data object.

Answer 1

You define private methods in the implementation file. If a method is not shown in the header file, then by definition, it is private. To clarify, the following is how you define public properties and methods.

@interface MyAppViewController : UIViewController

@property (strong, nonatomic) NSString *myPublicStringObject;

- (NSString *) myPublicMethodTakingInputString:(NSString *) input;

@end

In the implementation file, you can define private properties and methods as follows.

#import "MyAppViewController.h"

// Declare private properties and methods inside the following interface extension
@interface MyAppViewController ()

@property (strong, nonatomic) NSNumber     *myPrivateNumber;
@property (strong, nonatomic) NSString     *myPrivateStringObject;

- (void) myPrivateMethod1;
- (NSString *) myPrivateMethod2WithIntegerInput:(NSInteger) input;

@end


@implementation MyAppViewController

@synthesize myPublicStringObject;
@synthesize myPrivateNumber;
@synthesize myPrivateStringObject;

// Implement all methods declared in header and private interfaces here in no particular order
- (NSString *) myPublicMethodTakingInputString:(NSString *) input
{
// code for myPublicMethodTakingInputString
}

- (void) myPrivateMethod1
{
}

- (NSString *) myPrivateMethod2WithIntegerInput:(NSInteger) input
{
}


// Implement any other private method not declared
- (NSString *) myUndeclaredPrivateMethod1:(NSString *) input
{
// code for myUndeclaredPrivateMethod1
}


- (id) myUndeclaredPrivateMethod2
{
// code for myUndeclaredPrivateMethod2
}

… etc.

This description is for iOS 5 of course. The syntax for iOS3 & 4 is similar except that the private instant variables (iVars) appear in the header file–which could be very confusing for newbies. iOS 5 cleaned this up, by not requiring instant variables to appear anywhere.