iOS error "Initializing 'NSTimeInterval *' (aka 'double *')

Question

I'm trying to get the time interval between two NSDates, namely `previousActivity.stopTime`and `previousActivity.startTime`. I'm getting an error with this code: ``` NSTimeInterval *previousActivityDuration = [previousActivity.stopTime timeIntervalSinceDate:previousActivity.startTime]; ``` Here's the error message: `"Initializing 'NSTimeInterval *' (aka 'double *') with an expression of incompatible type 'NSTimeInterval' (aka 'double')"` I don't get it; If NSTimeInterval is aka 'double', how is the initialization expression incompatible, and how do I fix it? Many thanks! Edit: Per @Rmaddy's comment, I removed the asterisk. Then I get this error in the line immediately following: `Assigning to 'NSNumber *' from incompatible type 'NSTimeInterval' (aka 'double')` Here's the offending line: ``` previousActivity.duration = previousActivityDuration; ```

Accepted Answer

You're attempting to make an `NSTimeInterval` pointer variable, but what you really want is just an `NSTimeInterval` variable. So remove the asterisk like this:

```
NSTimeInterval previousActivityDuration = [previousActivity.stopTime timeIntervalSinceDate:previousActivity.startTime];
```

Your code was complaining because the types were different. Usually we only use pointers for Objective-C objects, and only where necessary do we generally use pointers for primitive types such as `double`s and such.

iOS error "Initializing 'NSTimeInterval ' (aka 'double ')

Solution

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