NSDateFormatter subtraction

Question

我有一个字段"From"one_answers"To"的日期选择器，我想要减法的结果。例如:toValue-fromValue，结果将以小时为单位。怎么做呢?

Answer 1

两个NSdate对象的差值可以用timeIntervalSinceDate计算:

NSTimeInterval diff = [toDate timeIntervalSinceDate:fromDate];

结果以秒为单位给出。然后，像这样计算小时数:

NSInteger hours = diff / 3600;

Answer 2

如果你有两个NSDate对象，你可以使用timeIntervalSinceDate方法比较它们

NSDate* fromDate = //Get from date picker
NSDate* toDate = //Get from date picker
NSTimeInterval = [fromDate timeIntervalSinceDate:toDate];
NSInteger hours = timeInterval / 60*60; //60 seconds per minute, 60 minutes per hour