create empty NSDate object

Question

Is this ok?

NSDate *myDate;

Because I used something like this before:

NSDate *myDate = [[NSDate alloc] init];

if (something)
     myDate = thisDate;
else
     myDate = thatDate;

[myFunction initWithDate:myDate];

I always got "Value stored to 'myDate' during its initialization is never read". If I do something like this

if (something)
     NSDate *myDate = thisDate;
else
     NSDate *myDate = thatDate;

[myFunction initWithDate:myDate];

I get "Unused variable 'myDate'" and "'myDate' undeclared (first use in this function)"

How does the release look like? Autorelease?

Answer 1

your first try was close

NSDate *myDate;

if (something)
     myDate = thisDate;
else
     myDate = thatDate;

[myFunction initWithDate:myDate];

First line declares an NSDate variable named myDate. Then you run your test and set the value of myDate appropriately.

Answer 2

If you just want to point to a pre-existing date, you could do something like this:

NSDate *myDate = something ? thisDate : thatDate;
[myFunction initWithDate:myDate];

or even

[myFunction initWithDate:something ? thisDate : thatDate];

However, to more clearly answer your question, yes, this could should be fine:

NSDate *myDate;

if (something) {
    myDate = thisDate;
} else {
    myDate = thatDate;
}

You can also initialize myDate to nil (myDate = nil), if you want.

As far as memory management goes, you're just setting a pointer -- you're not creating a new object, or taking ownership (via retain) of an existing object -- so you don't need to use release or autorelease at all.