NSDate的字符串描述

使用错误的方法。而应尝试 descriptionWithCalendarFormat：timeZone：locale：

You are using the wrong method. Instead try descriptionWithCalendarFormat:timeZone:locale:

[[NSDate date] descriptionWithCalendarFormat:@"%Y-%m-%d"
                                    timezone:nil
                                      locale:nil];

另请注意，该方法的格式与您问题中的格式不同。有关该文档的完整文档，请访问这里。

Also note that the method is expecting a different format than the one in your question. The full documentation for that can be found here.

编辑：虽然正如迈克所说，你真的应该使用 NSDateFormatter 。有些问题与Apple在文档中提到的 descriptionWithCalendarFormat：timezone：locale：有关。

Though as Mike noted, you really should be using NSDateFormatter. There are some problems with descriptionWithCalendarFormat:timezone:locale: that Apple mentions in the documentation.