将NSString转换为Double for NSTimeInterval

Question

The end result that I need is that I want to find out out how long ago a comment was posted. To do this I started off by doing something like:

double timestampComment = [[testArray objectForKey:@"timestamp"] doubleValue]/1000;
NSDate *date = [NSDate date];
NSLog(@"Date: %@", date);
NSTimeInterval timestamp = (NSTimeInterval)timestampComment;
NSDate *actualTime = [NSDate dateWithTimeInterval:timestamp sinceDate:date];

But that didn't work and returned something like 5213 months ago (it was only posted last week!) I then done some searching around and found out that the double value of the timestamp, ie 1377775454768 was actually 1377775454768.000000, so that explains why the timing was so wrong.

I've now tried done some console logging and still cant get the double value with no decimal values for the NSTimeInterval. This is what I have tried now:

double timer = [[testArray objectForKey:@"timestamp"]doubleValue];
        //NSString *timerStr = [NSString stringWithFormat:@"%.0f", timer];
        NSString *timerCount = [testArray objectForKey:@"timestamp"];

        NSTimeInterval timeIntervalComment = timer;
        //NSTimeInterval timeIntervalCount = timerCount;
        NSDate *date = [NSDate dateWithTimeIntervalSince1970:timeIntervalComment];
        NSLog(@"Timer: %@", timerCount);
       NSString *rightTimestr = [NSString stringWithFormat:@"%.0f", timeIntervalComment];
        int timerTest = [rightTimestr intValue];
        NSTimeInterval timeTest = (NSTimeInterval)[timerCount doubleValue];
        NSDate *testDate = [NSDate dateWithTimeIntervalSince1970:timeTest];
        NSLog(@"rightTimestr %@", rightTimestr);
        NSLog(@"timerTest %d", timerTest);
        NSLog(@"%f", [timerCount doubleValue]);
        NSLog(@"Test Date: %@", testDate);
        NSLog(@"Timer 2: %f", timer);
        NSLog(@"date: %@", date);

And this is the result of the logging:

Timer: 1377775454768
rightTimestr 1377775454768
timerTest 2147483647
1377775454768.000000
Test Date: 45629-12-19 04:06:08 +0000
Timer 2: 1377775454768.000000
date: 45629-12-19 04:06:08 +0000

Any help would be appreciated. Thanks

Answer 1

You want the difference in time between now and when the comment was posted. Untested:

double timestampComment = [[testArray objectForKey:@"timestamp"] doubleValue]/1000;
NSTimeInterval diff = (NSTimeInterval)timestampComment - [[NSDate date] timeIntervalSince1970];

// diff now contains the number of seconds since the comment was posted

However you don't want to use NSDate to format this difference, as NSDate is for manipulating dates, not time deltas. You'll need to use the kind of code used here on Stackoverflow to show when answers were posted, for example if < 1 hour then show "X minutes ago", else show the date the comment was posted, etc.