Private designated initializers in Objective-C

gistfile1.m

/*
My goal here is to have an immutable model class with an initialiser that is hidden unless you import a private header ("Person+Private.h"). This is useful in the context of providing a library or framework where consuming code only ever has read-only access to instances of this class, and they are never supposed to create instances themselves.
*/

…

//***********************************
// Person.h
//

@interface Person : NSObject

- (instancetype)init __attribute__((unavailable));

@property (readonly) NSString *name;
@property (readonly) NSInteger age;

@end

…

//***********************************
// Person+Private.h
//

#import "Person.h"

@interface Person ()

- (instancetype)initWithName:(NSString *)name age:(NSInteger)age;

@end