Check for multiple assignment to an ivar

gistfile1.m

NSString *const ASMultipleAssignmentException = @"Multiple Assignment Exception";

#ifndef CHECK_FOR_MULTI_ASSIGN
#define CHECK_FOR_MULTI_ASSIGN(ivar) \
    do { \
        if (ivar) { \
            NSString *AS_reason = @"Cannot assign to " #ivar " more than once"; \
            @throw [NSException exceptionWithName:ASMultipleAssignmentException \
                                           reason:AS_reason \
                                         userInfo:nil]; \
        } \
    } while(0)
#endif

- (void)setName:(NSString *)name
{
    CHECK_FOR_MULTI_ASSIGN(_name);
    _name = name;
}

- (void)setScore:(NSNumber *)score
{
    CHECK_FOR_MULTI_ASSIGN(_score);
    _score = score;
}

- (void)setWebsite:(NSURL *)website
{
    CHECK_FOR_MULTI_ASSIGN(_website);
    _website = website;
}