Casting an NSTimeInterval as a NSNumber within a block

Question

I'm having difficulty within a block with assigning an NSTimeInterval value to an NSNumber

Here is what I have so far:

[player addPeriodicTimeObserverForInterval:CMTimeMake(3, 10) queue:NULL usingBlock:^(CMTime time){
            NSTimeInterval seconds = CMTimeGetSeconds(time);
            NSNumber *lastTime = 0;
            for (NSDictionary *item in bualadhBos) {
                NSNumber *time = item[@"time"];
                if ( seconds > [time doubleValue] && seconds > [lastTime doubleValue]) {

                    lastTime = [seconds doubleValue];// this line causes difficulties
                    NSString *str = item[@"line"];
                    break;
                }; }

          }

I'm keeping track of time in an NSNumber and when the if statement is true I need to assign a new value to the variable lastTime - the problem is that I can't seem to figure out how to assign a NSTimeInterval Value contained in seconds to the variable lastTime that is of type NSNumber. I'm really confused as everything I read tells me that both are really just doubles. Any ideas?

NSTimeInterval is just an alias for the scalar/primitive `double` type, whereas NSNumber is a class. You cannot "cast" between a scalar and an object in Objective-C. — Hot Licks, Sep 23 '14 at 23:10

score 4 · Accepted Answer · answered Sep 23 '14 at 23:03

You need to understand that seconds is a primitive type (NSTimeInterval - really double). lastTime is the class type NSNumber.

To create an NSNumber from a primitive number type, you can do:

lastTime = @(seconds);

This is modern syntax for lastTime = [NSNumber numberWithDouble:seconds].

And the line NSNumber *lastTime = 0; is technically correct but not really and it's misleading. You want:

NSNumber *lastTime = nil;

Don't confuse primitive numbers with NSNumber and objects.

BTW - none of this is related to the use of a block.

Casting an NSTimeInterval as a NSNumber within a block

1 Answers1