设置方法所需静态对象的正确方法

发布于 2024-11-11 17:15:34 字数 644 浏览 0 评论 0原文

我正在 NSDate 上创建一个类别，将 NSDate 转换为 NSString。它使用 NSDateFormatter 来执行此操作。我发现每次分配然后取消分配格式化程序都会在我的应用程序中造成明显的延迟（此类别使用非常频繁），因此我更新了我的“格式”方法，如下所示：

- (NSString *)pretty
{   
    static NSDateFormatter *formatter = nil;

    if (formatter == nil)
    {
        formatter = [[NSDateFormatter alloc] init];
        [formatter setDateStyle:NSDateFormatterLongStyle];
        [formatter setTimeStyle:NSDateFormatterNoStyle];
    }

    return [formatter stringFromDate:self];
}

这是处理静态变量的正确方法吗？可可？这是泄漏吗（alloc 之后没有 dealloc）？是否存在更好的方法来做这样的事情？谢谢！

原文

I'm creating a category on NSDate that that converts a NSDate into a NSString. It uses an NSDateFormatter to do so. I found that allocating then deallocating the formatter each time was causing noticeable delays in my application (this category is used very frequently), so I updated my 'format' method to look like this:

- (NSString *)pretty
{   
    static NSDateFormatter *formatter = nil;

    if (formatter == nil)
    {
        formatter = [[NSDateFormatter alloc] init];
        [formatter setDateStyle:NSDateFormatterLongStyle];
        [formatter setTimeStyle:NSDateFormatterNoStyle];
    }

    return [formatter stringFromDate:self];
}

Is this the correct way to handle a static variable in Cocoa? Is this a leak (no dealloc after alloc)? Does a better way exist of doing something like this? Thanks!

分享到QQ

分享到微博

如果你对这篇内容有疑问，欢迎到本站社区发帖提问参与讨论，获取更多帮助，或者扫码二维码加入 Web 技术交流群。

发布评论

需要登录才能够评论，你可以免费注册一个本站的账号。

秋心╮凉 2024-11-18 17:15:34

您正在有效地创建一个单例。除非不会在应用程序的整个运行会话中使用它，否则不必担心内存使用。即使它只是间歇性地使用，保留一个日期格式化程序也不会成为问题。

即就像单例一样，不必担心在应用程序终止之前释放对象。

如果 pretty 被多个线程攻击（并且假设 NSDateFormatter 本身是线程安全的——我没有检查文档，因此，不要写代码没有验证线程安全），那么你想要保护初始化。

static dispatch_once_t onceMark;
static NSDateFormatter *formatter = nil;
dispatch_once(&onceMark, ^{
        formatter = [[NSDateFormatter alloc] init];
        [formatter setDateStyle:NSDateFormatterLongStyle];
        [formatter setTimeStyle:NSDateFormatterNoStyle];
});

You are effectively creating a singleton. Unless it isn't going to be used throughout the entire running session of your application, don't worry about the memory use. Even if it is only going to be used intermittently, leaving one date formatter around isn't going to be an issue.

I.e. just like a singleton, don't worry about releasing the object prior to application termination.

If pretty were to be pounded on from multiple threads (and assuming that NSDateFormatter itself is thread safe -- I didn't check the docs and, thus, don't write the code without verifying thread safety), then you'd want to protect the initialization.

static dispatch_once_t onceMark;
static NSDateFormatter *formatter = nil;
dispatch_once(&onceMark, ^{
        formatter = [[NSDateFormatter alloc] init];
        [formatter setDateStyle:NSDateFormatterLongStyle];
        [formatter setTimeStyle:NSDateFormatterNoStyle];
});

回复收藏 0 原文