如何在Cocoa中获得本月的最后一天？

// 获取当前日期
NSDate *currentDate = [NSDate date];

// 创建一个NSCalendar对象
NSCalendar *calendar = [NSCalendar currentCalendar];

// 获取当前月份的下个月的第一天
NSDateComponents *components = [[NSDateComponents alloc] init];
components.month = 1;
components.day = 1;
NSDate *nextMonthFirstDay = [calendar dateByAddingComponents:components toDate:currentDate options:0];

// 获取当前月份的最后一天
components = [[NSDateComponents alloc] init];
components.month = -1;
components.day = 0;
NSDate *lastMonthLastDay = [calendar dateByAddingComponents:components toDate:nextMonthFirstDay options:0];

// 格式化日期
NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
[formatter setDateFormat:@"yyyy-MM-dd"];
NSString *lastDayOfMonth = [formatter stringFromDate:lastMonthLastDay];

NSLog(@"本月的最后一天是：%@", lastDayOfMonth);