Question

我在网上找到以下代码来比较两个日期（日历日期和另一个日期）我想要帮助的是修改此代码，以便将日历日期与日期事件的日期进行比较这里是NSArray（json文件）中每个事件的关键。另外我以后如何在NSPredicate中使用它，以便我可以加载至少有超过1天的组件事件（两个日期之间的差异）至少1天当用户点击它时，让UIButton调用未来事件，应该加载所有未来事件。我非常感谢任何帮助和代码示例，因为我对目标C和Xcode非常新。感谢。

@implementation HomeViewController {
    NSArray *_events;
}

- (BOOL)isSameDay:(NSDate*)date
{
    NSCalendar* calendar = [NSCalendar currentCalendar];
    NSDate *currDate = [NSDate date];
    //date = [_events objectAtIndex:date];

    unsigned unitFlags = NSYearCalendarUnit | NSMonthCalendarUnit |  NSDayCalendarUnit;
    NSDateComponents* comp1 = [calendar components:unitFlags fromDate:date];
    NSDateComponents* comp2 = [calendar components:unitFlags fromDate:currDate];
    NSDateComponents *components = [calendar components:unitFlags
                                               fromDate:currDate
                                                 toDate:date
                                                options:0];

    NSLog(@"Days between dates: %@", components);

    return [comp1 day]   == [comp2 day] &&
    [comp1 month] == [comp2 month] &&
    [comp1 year]  == [comp2 year];
}

Answer 1

要获取从现在开始的日期剩余天数，您可以使用以下方法：

-(long)daysRemaining:(NSDate*) date
{
    NSDate *now = [NSDate date];
    NSTimeInterval dateDiff = [date timeIntervalSinceNow] - [now timeIntervalSinceNow];
    CGFloat numberOfDaysRemaining = (dateDiff/(60*60*24));
    return ceil(numberOfDaysRemaining);
}

所以你可以打电话来获得这样的剩余天数：

NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
[dateFormatter setDateFormat:@"yyyy-MM-dd"];
NSDate *dateToCompare = [dateFormatter dateFromString: @"2014-02-08"];

long numberDays = [self daysRemaining:dateToCompare];

对于这种情况，结果是 2 天。请注意，否定结果表示已通过 n 天。

过滤数组（剩余2天事件）制作副本：

NSArray* dates = [[NSArray alloc] initWithObjects:
    [dateFormatter dateFromString: @"2014-02-08"],
    [dateFormatter dateFromString: @"2014-02-05"],
    [dateFormatter dateFromString: @"2014-02-10"],
    [dateFormatter dateFromString: @"2014-02-08"], nil];

NSArray *filteredArray = [dates filteredArrayUsingPredicate:
    [NSPredicate predicateWithBlock:
        ^BOOL(id evaluatedObject, NSDictionary *bindings) {
            long daysRemaining = [self daysRemaining:(NSDate*)evaluatedObject];
            return daysRemaining == 2; // if someMethod returns YES, the object is kept
        }
    ]];

过滤NSMutableArray：

[mutableArray filterUsingPredicate:[NSPredicate predicateWithBlock:
    ^BOOL(id evaluatedObject, NSDictionary *bindings) {
        long daysRemaining = [self daysRemaining:(NSDate*)evaluatedObject];
        return daysRemaining == 2; // if someMethod returns YES, the object is kept
    }
]];

Answer 2

  [displayedEvents addObjectsFromArray:[_events filteredArrayUsingPredicate:
                          [NSPredicate predicateWithBlock:
                           ^BOOL(Events * event, NSDictionary *bindings) {
                               [dateFormatter dateFromString: event.date];
                               long daysRemaining = [self daysRemaining: (NSDate*)event.date];
                               return daysRemaining > 1; // if someMethod returns YES, the object is kept
                           }
  ]]];

通过将日期与日历日期进行比较来加载即将发生的事件

2 个答案: