ios - 单击下一个和上一个UIButton时在UILabel中更改日期

Question

在UILabel中设置一个日期。
单击“下一个”和“上一个”按钮应更改此标签内的日期。

我正在尝试此代码，但是单击下一个按钮并显示日期第二天日期为例如01/05/2015和上一个按钮单击并设置日期为29/05/2015，下一个按钮单击则不显示02/05/2015

- (IBAction)changeToNextDay:(id)sender
{
    NSDateComponents* deltaComps = [[NSDateComponents alloc] init];
    [deltaComps setDay:+1];
    NSDate* tomorrow = [[NSCalendar currentCalendar]  dateByAddingComponents:deltaComps toDate:[NSDate date] options:0];

    NSDateFormatter *myDateFormatter = [[NSDateFormatter alloc] init];
    [myDateFormatter setDateFormat:@"dd-MM-yyyy"];

    NSString *stringFromDate = [myDateFormatter  stringFromDate:tomorrow];
    dateLabel.text = stringFromDate;
}

- (IBAction)changeToPreviousDay:(id)sender
{
    NSDate *datePlusOneDay = [[NSDate date] dateByAddingTimeInterval:-(60 * 60 * 24)];
    NSLog(@"datePlusOneDay=%@",datePlusOneDay);

    NSDateFormatter *myDateFormatter = [[NSDateFormatter alloc] init];
    [myDateFormatter setDateFormat:@"dd-MM-yyyy"];

    NSString *stringFromDate = [myDateFormatter stringFromDate:datePlusOneDay];
    dateLabel.text = stringFromDate;
}

Answer 1

- (void)viewDidLoad {
    [super viewDidLoad];
    [self Update_Date_By:0];
}

- (IBAction)changeToNextDay:(id)sender {
    [self Update_Date_By:1];
}

- (IBAction)changeToPreviousDay:(id)sender {
    [self Update_Date_By:-1];
}

-(void)Update_Date_By:(NSInteger)value {
    NSDateFormatter *dateFormat = [[NSDateFormatter alloc] init];
    [dateFormat setDateFormat:@"dd/MM/yyyy"];
    NSDate *date = [dateFormat dateFromString:dateLabel.text];
    NSCalendar *calendar = [NSCalendar currentCalendar];
    NSDateComponents *dateComponents = [NSDateComponents new];
    dateComponents.day = value;
    if (value == 0) {
        date = [NSDate date];
    }
    NSDate *newDate = [calendar dateByAddingComponents:dateComponents toDate:date options:0];
    [dateFormat setDateFormat:@"dd/MM/yyyy"];
    NSString *finalDate_String = [dateFormat stringFromDate:newDate];
    dateLabel.text = finalDate_String;
}