在Objective-C类别中初始化静态变量 [英] Initialising a static variable in Objective-C category

问题描述

我试图创建一个静态变量来存储图像字典.不幸的是，我能找到的最好的初始化方法是检入使用该变量的每个函数.由于我是在类别中创建此变量的，所以不能只在初始化程序中对其进行初始化.有没有更整洁的方法来初始化navigationBarImages?

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

推荐答案

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

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

在程序开始和结束时将自动调用这些函数.

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

这篇关于在Objective-C类别中初始化静态变量的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！