ios - 定义ivar的最佳方式是什么？

Question

我定义了三个属性，一个 UISearchBar，NSDicitonary 类型和 NSArray 类型。

它们之间有什么区别？ ( self 。)或(_)

原因是什么？

@property (nonatomic, strong, readwrite) UISearchBar  *searchBar;
@property (nonatomic, strong)            NSDictionary *citiesDataDic;
@property (nonatomic, strong)            NSArray      *initialOfCity;

第一种方式:

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
   NSString *key = [_initialOfCity objectAtIndex:section];
   NSArray *citySection = [_citiesDataDic objectForKey:key];
   return [citySection count];
}


- (void)viewDidLoad
{
   [super viewDidLoad];
   NSString *path = [[NSBundle mainBundle] pathForResource:@"citydict"
                                                 ofType:@"plist"];
   _citiesDataDic = [[NSDictionary alloc] initWithContentsOfFile:path];
   _initialOfCity = [[_citiesDataDic allKeys] sortedArrayUsingSelector:@selector(compare:)];

   _searchBar = [[UISearchBar alloc] initWithFrame:CGRectZero];
   _searchBar.placeholder = @"enter words";
   _searchBar.delegate = self;
  [_searchBar sizeToFit];
}

第二种方式:

   NSString *key = [self.initialOfCity objectAtIndex:section];
   NSArray *citySection = [self.citiesDataDic objectForKey:key];
   return [citySection count];

   [super viewDidLoad];
   NSString *path = [[NSBundle mainBundle] pathForResource:@"citydict"
                                                 ofType:@"plist"];
   self.citiesDataDic = [[NSDictionary alloc] initWithContentsOfFile:path];
   self.initialOfCity = [[self.citiesDataDic allKeys] sortedArrayUsingSelector:@selector(compare:)];

   self.searchBar = [[UISearchBar alloc] initWithFrame:CGRectZero];
   self.searchBar.placeholder = @"enter words";
   self.searchBar.delegate = self;
  [self.searchBar sizeToFit];

Answer 1

readwrite

这个限定符是不必要的，因为它是默认行为。不要使用它，否则可能会使人感到困惑。

self. 语法调用属性的 getter 和 setter，可以通过 propertyName 或 setPropertyName 明确定义。

尝试使用 self. 语法，因为如果有一天您需要 getter 或 setter，它会使事情变得更容易。通过 _ 语法访问属性将直接访问属性，即使定义了 getter/setter。