ios - 不会改变的 NSDictionary

Question

我想让自己的事情变得更容易，所以我正在创建一个字典，供其他函数使用(按对象或按键访问对象)，但该字典始终是静态的。这是做这件事的好方法还是我需要属性(property)或其他东西？

+ (NSDictionary *)dictionaryWithCategoriesAndStrings
{
    return @{
             kNewsCategoryAll       : @(NewsCategoryAll),
             kNewsCategoryRadio     : @(NewsCategoryRadio),
             kNewsCategoryEconomics : @(NewsCategoryEconomics),
             kNewsCategoryCulture   : @(NewsCategoryCulture),
             kNewsCategorySport     : @(NewsCategorySport),
             kNewsCategoryTravel    : @(NewsCategoryTravel),
             kNewsCategoryMusic     : @(NewsCategoryMusic),
             kNewsCategorySociety   : @(NewsCategorySociety),
             kNewsCategoryHealth    : @(NewsCategoryHealth)
             };
}

所以现在我总是通过函数 [self dictionaryWithCategoriesAndString] 访问同一个字典；

注意:这些键是在顶部声明的静态字符串，对象是带整数的 NSNumber。

Answer 1

与其将静态暴露给整个类，不如在方法中创建它，并使用 gcd 仅初始化一次:

这是线程安全的。

+ (NSDictionary *)dictionaryWithCategoriesAndStrings {
    static NSDictionary *dict;

    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        dict = @{
                 kNewsCategoryAll       : @(NewsCategoryAll),
                 kNewsCategoryRadio     : @(NewsCategoryRadio),
                 kNewsCategoryEconomics : @(NewsCategoryEconomics),
                 kNewsCategoryCulture   : @(NewsCategoryCulture),
                 kNewsCategorySport     : @(NewsCategorySport),
                 kNewsCategoryTravel    : @(NewsCategoryTravel),
                 kNewsCategoryMusic     : @(NewsCategoryMusic),
                 kNewsCategorySociety   : @(NewsCategorySociety),
                 kNewsCategoryHealth    : @(NewsCategoryHealth)
                 };
    });

    return dict;
}