On 3-Jun-08, at 12:08 PM, Shawn Erickson wrote:
On Tue, Jun 3, 2008 at 8:56 AM, Karl Moskowski <[EMAIL PROTECTED]> wrote:I have a few methods that return NSData objects, but the objects are created and manipulated as NSMutableData, and then copied to an immutable versionalong these lines: NSMutableData *myData = [NSMutableData data]; : : return [NSData dataWithData:myData]; Would it be sufficient to cast, like this? : return (NSData *)myData; Does this generalize to other non-collection classes, e.g., NSString?It fully depends what the caller expects (aka how you document it). If they expect the data instance they get back to not change on them while they hold a reference (what you imply by saying you return an immutable object) then you need to ensure that holds true either by copying it before you return it or by not modifying it during some well defined (documented) scope/window of time.
For now, at least, I'm the only caller, but that could change in the future.
If you populate the mutable object and never touch it again then you likely can happily return that instance cast as an NSData since your API states that the caller should consider it immutable ... however be aware that the caller may make assumptions about the cost of copying (no-op for immutable objects) and that assumption could be invalidated when you return a mutable object instead of the promised immutable object.
That's what I wanted to know. Thanks. ---- Karl Moskowski <[EMAIL PROTECTED]> Voodoo Ergonomics Inc. <http://voodooergonomics.com/>
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