在 Objective-C 类别中初始化静态变量

发布于 2024-08-17 16:43:41 字数 960 浏览 2 评论 0原文

我试图创建一个静态变量来存储图像字典。不幸的是，我能找到的初始化它的最好方法是检查使用该变量的每个函数。由于我是在类别内创建此变量，因此我不能仅在初始化程序内初始化它。有没有更简洁的方法来初始化 navigationBarImages？

static NSMutableDictionary *navigationBarImages = NULL;

@implementation UINavigationBar(CustomImage)
//Overrider to draw a custom image
- (void)drawRect:(CGRect)rect
{
    if(navigationBarImages==NULL){
        navigationBarImages=[[NSMutableDictionary alloc] init];
    }
    NSString *imageName=[navigationBarImages objectForKey:self];
    if (imageName==nil) {
        imageName=@"header_bg.png";
    }
    UIImage *image = [UIImage imageNamed: imageName];
    [image drawInRect:CGRectMake(0, 0, self.frame.size.width, self.frame.size.height)];
}

//Allow the setting of an image for the navigation bar
- (void)setImage:(UIImage*)image
{
    if(navigationBarImages==NULL){
        navigationBarImages=[[NSMutableDictionary alloc] init];
    }
    [navigationBarImages setObject:image forKey:self];
}
@end

原文

I was trying to create a static variable to store a dictionary of images. Unfortunately, the best way I could find to initialise it was to check in each function that used the variable. Since I am creating this variable inside a category, I can't just initialise it inside the initialiser. Is there a neater way of initialising navigationBarImages?

static NSMutableDictionary *navigationBarImages = NULL;

@implementation UINavigationBar(CustomImage)
//Overrider to draw a custom image
- (void)drawRect:(CGRect)rect
{
    if(navigationBarImages==NULL){
        navigationBarImages=[[NSMutableDictionary alloc] init];
    }
    NSString *imageName=[navigationBarImages objectForKey:self];
    if (imageName==nil) {
        imageName=@"header_bg.png";
    }
    UIImage *image = [UIImage imageNamed: imageName];
    [image drawInRect:CGRectMake(0, 0, self.frame.size.width, self.frame.size.height)];
}

//Allow the setting of an image for the navigation bar
- (void)setImage:(UIImage*)image
{
    if(navigationBarImages==NULL){
        navigationBarImages=[[NSMutableDictionary alloc] init];
    }
    [navigationBarImages setObject:image forKey:self];
}
@end

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扎心 2024-08-24 16:43:41

__attribute__((constructor))
static void initialize_navigationBarImages() {
  navigationBarImages = [[NSMutableDictionary alloc] init];
}

__attribute__((destructor))
static void destroy_navigationBarImages() {
  [navigationBarImages release];
}

这些函数将在程序启动和结束时自动调用。

__attribute__((constructor))
static void initialize_navigationBarImages() {
  navigationBarImages = [[NSMutableDictionary alloc] init];
}

__attribute__((destructor))
static void destroy_navigationBarImages() {
  [navigationBarImages release];
}

These function will be called automatically when the program starts and ends.

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海未深 2024-08-24 16:43:41

考虑这种方法，

static NSMutableDictionary *navigationBarImages()
{
    static NSMutableDictionary *dict = NULL;
    if(dict == NULL)
    {
        dict = [[NSMutableDictionary alloc] init];
    }
    return [[dict retain] autorelease];
}

然后每当您要使用 navigationBarImages 时，将其替换为 navigationBarImages()，如下所示：

更改

NSString *imageName=[navigationBarImages objectForKey:self];

为

NSString *imageName=[navigationBarImages() objectForKey:self];

如果函数调用开销困扰您，也许可以使用临时变量捕获navigationBarImages()的返回，

NSMutableDictionary *dict = navigationBarImages();
[dict doSomething];
[dict doSomething];

缺点是一旦你调用navigationBarImages()，NSMutableDictionary的实例被创建，那么它永远不会有机会释放，直到程序结束。

Consider this approach,

static NSMutableDictionary *navigationBarImages()
{
    static NSMutableDictionary *dict = NULL;
    if(dict == NULL)
    {
        dict = [[NSMutableDictionary alloc] init];
    }
    return [[dict retain] autorelease];
}

then whenever you woulde use navigationBarImages, replace it with navigationBarImages(), like this:

change

NSString *imageName=[navigationBarImages objectForKey:self];

NSString *imageName=[navigationBarImages() objectForKey:self];

If the function call overhead bothers you, maybe use a temporary variable to catch the return of navigationBarImages(),

NSMutableDictionary *dict = navigationBarImages();
[dict doSomething];
[dict doSomething];

The drawback is once you called navigationBarImages(), the instance of NSMutableDictionary got created, then it'll never get chance to dealloc until the end of the program.

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