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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