Immutable & mutable models

option1.h

@interface TMUser1 : NSObject <NSCopying, NSMutableCopying>

@property (nonatomic, copy, readonly) NSString *userId;
@property (nonatomic, copy, readonly) NSString *name;
@property (nonatomic, copy, readonly) NSString *surname;
@property (nonatomic, readonly) NSURL *avatarURL;

- (instancetype)initWithUserId:(NSString *)userId
			  name:(NSString *)name
		       surname:(NSString *)surname
		     avatarURL:(NSURL *)avatarURL;

@end

@interface TMMutableUser1 : TMUser1

@property (nonatomic, copy) NSString *userId;
@property (nonatomic, copy) NSString *name;
@property (nonatomic, copy) NSString *surname;
@property (nonatomic) NSURL *avatarURL;

@end

option1.m

@interface TMUser1 ()

@property (nonatomic, copy) NSString *userId;
@property (nonatomic, copy) NSString *name;
@property (nonatomic, copy) NSString *surname;
@property (nonatomic) NSURL *avatarURL;

@end

@implementation TMUser1

- (instancetype)initWithUserId:(NSString *)userId
			  name:(NSString *)name
		       surname:(NSString *)surname
		     avatarURL:(NSURL *)avatarURL
{
	self = [super init];
	if (self)
	{
		_userId = [userId copy];
		_name = [name copy];
		_surname = [surname copy];
		_avatarURL = avatarURL;
	}
	return self;
}

- (TMUser1 *)copyWithZone:(NSZone *)zone
{
	return self;
}

- (TMMutableUser1 *)mutableCopyWithZone:(NSZone *)zone
{
	return [[TMMutableUser1 alloc] initWithUserId:self.userId
						 name:self.name
					      surname:self.surname
					    avatarURL:self.avatarURL];
}

@end

@implementation TMMutableUser1

@dynamic userId;
@dynamic name;
@dynamic surname;
@dynamic avatarURL;

- (TMUser1 *)copyWithZone:(NSZone *)zone
{
	return [[TMUser1 alloc] initWithUserId:self.userId
					  name:self.name
				       surname:self.surname
				     avatarURL:self.avatarURL];
}

@end

option2.h

@interface TMUser2 : NSObject <NSCopying, NSMutableCopying>

@property (nonatomic, copy, readonly) NSString *userId;
@property (nonatomic, copy, readonly) NSString *name;
@property (nonatomic, copy, readonly) NSString *surname;
@property (nonatomic, readonly) NSURL *avatarURL;

- (instancetype)initWithUserId:(NSString *)userId
			  name:(NSString *)name
		       surname:(NSString *)surname
		      avatarURL:(NSURL *)avatarURL;

@end

@protocol TMMutableUser2 <NSObject>

@property (nonatomic, copy) NSString *userId;
@property (nonatomic, copy) NSString *name;
@property (nonatomic, copy) NSString *surname;
@property (nonatomic) NSURL *avatarURL;

@end

typedef TMUser2<TMMutableUser2> TMMutableUser2;

option2.m

@interface TMUser2 ()

@property (nonatomic, copy) NSString *userId;
@property (nonatomic, copy) NSString *name;
@property (nonatomic, copy) NSString *surname;
@property (nonatomic) NSURL *avatarURL;

@end

@implementation TMUser2

- (instancetype)initWithUserId:(NSString *)userId
			  name:(NSString *)name
		       surname:(NSString *)surname
		      avatarURL:(NSURL *)avatarURL
{
	self = [super init];
	if (self)
	{
		_userId = [userId copy];
		_name = [name copy];
		_surname = [surname copy];
		_avatarURL = avatarURL;
	}
	return self;
}

- (TMUser2 *)copyWithZone:(NSZone *)zone
{
	return [[TMUser2 alloc] initWithUserId:self.userId
					  name:self.name
				       surname:self.surname
				     avatarURL:self.avatarURL];
}

- (TMMutableUser2 *)mutableCopyWithZone:(NSZone *)zone
{
	return [self copyWithZone:zone];
}

@end

option3.h

@interface TMUser3 : NSObject <NSCopying, NSMutableCopying>

@property (nonatomic, copy, readonly) NSString *userId;
@property (nonatomic, copy, readonly) NSString *name;
@property (nonatomic, copy, readonly) NSString *surname;
@property (nonatomic, readonly) NSURL *avatarURL;

- (instancetype)initWithUserId:(NSString *)userId
			  name:(NSString *)name
		       surname:(NSString *)surname
		     avatarURL:(NSURL *)avatarURL;

@end

@interface TMMutableUser3 : TMUser3

@property (nonatomic, copy) NSString *userId;
@property (nonatomic, copy) NSString *name;
@property (nonatomic, copy) NSString *surname;
@property (nonatomic) NSURL *avatarURL;

@end

option3.m

@implementation TMUser3

- (instancetype)initWithUserId:(NSString *)userId
			  name:(NSString *)name
		       surname:(NSString *)surname
		     avatarURL:(NSURL *)avatarURL
{
	self = [super init];
	if (self)
	{
		_userId = [userId copy];
		_name = [name copy];
		_surname = [surname copy];
		_avatarURL = avatarURL;
	}
	return self;
}

- (TMUser3 *)copyWithZone:(NSZone *)zone
{
	return self;
}

- (TMMutableUser3 *)mutableCopyWithZone:(NSZone *)zone
{
	return [[TMMutableUser3 alloc] initWithUserId:self.userId
						 name:self.name
					      surname:self.surname
					    avatarURL:self.avatarURL];
}

@end

@interface TMMutableUser3 ()

@property (nonatomic, copy) NSString *mutableUserId;
@property (nonatomic, copy) NSString *mutableName;
@property (nonatomic, copy) NSString *mutableSurname;
@property (nonatomic, copy) NSURL *mutableAvatarURL;

@end

@implementation TMMutableUser3

- (instancetype)initWithUserId:(NSString *)userId
			  name:(NSString *)name
		       surname:(NSString *)surname
		     avatarURL:(NSURL *)avatarURL
{
	self = [super init];
	if (self)
	{
		_mutableUserId = [userId copy];
		_mutableName = [name copy];
		_mutableSurname = [surname copy];
		_mutableAvatarURL = avatarURL;
	}
	return self;
}

- (TMUser1 *)copyWithZone:(NSZone *)zone
{
	return [[TMUser1 alloc] initWithUserId:self.userId
					  name:self.name
				       surname:self.surname
				     avatarURL:self.avatarURL];
}

- (NSString *)userId
{
	return self.mutableUserId;
}

- (void)setUserId:(NSString *)userId
{
	self.mutableUserId = userId;
}

- (NSString *)name
{
	return self.mutableName;
}

- (void)setName:(NSString *)name
{
	self.mutableName = name;
}

- (NSString *)surname
{
	return self.mutableSurname;
}

- (void)setSurname:(NSString *)surname
{
	self.mutableSurname = surname;
}

- (NSURL *)avatarURL
{
	return self.mutableAvatarURL;
}

- (void)setAvatarURL:(NSURL *)avatarURL
{
	self.mutableAvatarURL = avatarURL;
}

@end

option4.h

@interface TMUser4 : NSObject <NSCopying, NSMutableCopying>

@property (nonatomic, copy, readonly) NSString *userId;
@property (nonatomic, copy, readonly) NSString *name;
@property (nonatomic, copy, readonly) NSString *surname;
@property (nonatomic, readonly) NSURL *avatarURL;

- (instancetype)initWithUserId:(NSString *)userId
			  name:(NSString *)name
		       surname:(NSString *)surname
		     avatarURL:(NSURL *)avatarURL;

@end

@interface TMMutableUser4 : TMUser4

@property (nonatomic, copy) NSString *userId;
@property (nonatomic, copy) NSString *name;
@property (nonatomic, copy) NSString *surname;
@property (nonatomic) NSURL *avatarURL;

@end

option4.m

@interface TMUser4 ()
{
@protected
	NSString *_userId;
	NSString *_name;
	NSString *_surname;
	NSURL *_avatarURL;
}

@end

@implementation TMUser4

- (instancetype)initWithUserId:(NSString *)userId
			  name:(NSString *)name
		       surname:(NSString *)surname
		     avatarURL:(NSURL *)avatarURL
{
	self = [super init];
	if (self)
	{
		_userId = [userId copy];
		_name = [name copy];
		_surname = [surname copy];
		_avatarURL = avatarURL;
	}
	return self;
}

- (TMUser4 *)copyWithZone:(NSZone *)zone
{
	return self;
}

- (TMMutableUser4 *)mutableCopyWithZone:(NSZone *)zone
{
	return [[TMMutableUser4 alloc] initWithUserId:self.userId
						 name:self.name
					      surname:self.surname
					    avatarURL:self.avatarURL];
}

@end

@implementation TMMutableUser4

@dynamic userId;
@dynamic name;
@dynamic surname;
@dynamic avatarURL;

- (TMUser4 *)copyWithZone:(NSZone *)zone
{
	return [[TMUser4 alloc] initWithUserId:self.userId
					  name:self.name
				       surname:self.surname
				     avatarURL:self.avatarURL];
}

- (void)setUserId:(NSString *)userId
{
	_userId = [userId copy];
}

- (void)setName:(NSString *)name
{
	_name = [name copy];
}

- (void)setSurname:(NSString *)surname
{
	_surname = [surname copy];
}

- (void)setAvatarURL:(NSURL *)avatarURL
{
	_avatarURL = avatarURL;
}

@end

option5.h

@protocol TMUser5 <NSCopying, NSMutableCopying>

@property (nonatomic, copy, readonly) NSString *userId;
@property (nonatomic, copy, readonly) NSString *name;
@property (nonatomic, copy, readonly) NSString *surname;
@property (nonatomic, readonly) NSURL *avatarURL;

@end

@interface TMMutableUser5 : NSObject <TMUser5>

@property (nonatomic, copy) NSString *userId;
@property (nonatomic, copy) NSString *name;
@property (nonatomic, copy) NSString *surname;
@property (nonatomic, readonly) NSURL *avatarURL;

- (instancetype)initWithUserId:(NSString *)userId
			  name:(NSString *)name
		       surname:(NSString *)surname
		     avatarURL:(NSURL *)avatarURL;

@end

typedef NSObject<TMUser5> TMUser5;

option5.m

@implementation TMMutableUser5

- (instancetype)initWithUserId:(NSString *)userId
			  name:(NSString *)name
		       surname:(NSString *)surname
		     avatarURL:(NSURL *)avatarURL
{
	self = [super init];
	if (self)
	{
		_userId = [userId copy];
		_name = [name copy];
		_surname = [surname copy];
		_avatarURL = avatarURL;
	}
	return self;
}

- (id<TMUser5>)copyWithZone:(NSZone *)zone
{
	return [[TMMutableUser5 alloc] initWithUserId:self.userId
						 name:self.name
					      surname:self.surname
					    avatarURL:self.avatarURL];
}

- (TMMutableUser5 *)mutableCopyWithZone:(NSZone *)zone
{
	return [self copyWithZone:zone];
}

@end

option6+mutability.h

@interface TMUser6 (Mutability)

@property (nonatomic, copy) NSString *userId;
@property (nonatomic, copy) NSString *name;
@property (nonatomic, copy) NSString *surname;
@property (nonatomic) NSURL *avatarURL;

@end

option6.h

@interface TMUser6 : NSObject <NSCopying, NSMutableCopying>

@property (nonatomic, copy, readonly) NSString *userId;
@property (nonatomic, copy, readonly) NSString *name;
@property (nonatomic, copy, readonly) NSString *surname;
@property (nonatomic, readonly) NSURL *avatarURL;

- (instancetype)initWithUserId:(NSString *)userId
			  name:(NSString *)name
		       surname:(NSString *)surname
		     avatarURL:(NSURL *)avatarURL;

@end

option6.m

@interface TMUser6 ()

@property (nonatomic, copy) NSString *userId;
@property (nonatomic, copy) NSString *name;
@property (nonatomic, copy) NSString *surname;
@property (nonatomic) NSURL *avatarURL;

@end

@implementation TMUser6

- (instancetype)initWithUserId:(NSString *)userId
			  name:(NSString *)name
		       surname:(NSString *)surname
		     avatarURL:(NSURL *)avatarURL
{
	self = [super init];
	if (self)
	{
		_userId = [userId copy];
		_name = [name copy];
		_surname = [surname copy];
		_avatarURL = avatarURL;
	}
	return self;
}

- (TMUser6 *)copyWithZone:(NSZone *)zone
{
	return [[TMUser6 alloc] initWithUserId:self.userId
					  name:self.name
				       surname:self.surname
				     avatarURL:self.avatarURL];
}

- (TMUser6 *)mutableCopyWithZone:(NSZone *)zone
{
	return [self copyWithZone:zone];
}

@end

Yeah, @cesteban, I wrote the ones that kept the NSCopying/NSMutableCopying interface, because I thought that we already voted for it in the arch committee after testing it in the field.

However we can decide it again if we see that other option with a different API will be better for us. That can open a can of worms too :P because then we have another option: to just publish the initialize and that's just it. TMPhoneNumber follows that option, and it has resulted in an explosion of initializers :/