On Feb 27, 2013, at 1:12 PM, Brad O'Hearne <br...@bighillsoftware.com> wrote:
> I have a need to construct an object with the possibility of an error taking
> place and needing to return that error. While it would be nice to have a
> clean init method that returned no errors, in this particular case, the error
> belongs with init. I've been pondering two ways of doing this:
>
> 1. Just a modified init method, where it returns nil for the return value and
> sets an error pointer like so:
>
> - (id)init:(NSError **)error;
> {
> self = [super init];
>
> if (self)
> {
> if ([self operationThatMightFail:error])
> {
> *error = nil;
> }
> else
> {
> return nil;
> }
> }
>
> return self;
> }
>
> OR
>
> 2. Using a static method to perform the dirty work, and then encouraging the
> caller only to use this method to init the class, like so:
>
> - (AThing *)athing:(NSError **)error;
> {
> AThing *a = [[AThing alloc] init];
>
> if ([a operationThatMightFail:error])
> {
> *error = nil;
> }
> else
> {
> return nil;
> }
>
> return a;
> }
>
> What is the recognized convention or design pattern for addressing this in
> Objective C, or does it not really matter?
Overall, I think that a factory method is a better design than tying this to
allocation/initialization.
John.
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