Re: Constructing class names dynamically
Re: Constructing class names dynamically
- Subject: Re: Constructing class names dynamically
- From: "Mohan Parthasarathy" <email@hidden>
- Date: Tue, 13 Jan 2009 20:45:52 -0800
On Tue, Jan 13, 2009 at 8:06 PM, Ken Thomases <email@hidden> wrote:
> On Jan 13, 2009, at 3:33 PM, Jean-Daniel Dupas wrote:
>
> he is just talking about class name, not class.
>>
>> NSClassFromString() is probably what you're looking for.
>>
>> NSMutableString *clsName = derive class name from the entry.
>>
>> Class cls = NSClassFromString(clsName);
>>
>> id<YouProtocol> instance = [[cls alloc] init];
>>
>
> I'll just add the following:
>
> If you don't need such complete flexibility -- for example, if you're
> selecting from a fixed set of classes by some tag -- then you don't need to
> compute a class name and look up the class that way.
>
> Classes are objects and so they can be stored in collections. For example,
> you could have a lookup dictionary that mapped from keys to class objects.
> You would construct the dictionary like this:
>
> [NSDictionary dictionaryWithObjectsAndKeys:
> [SomeClass class], "key1",
> [OtherClass class], "key2",
> [ThirdClass class], "key3",
> // ... etc.
> nil];
>
> This adds a small amount of safety in the same way that
> statically-specified stuff generally does. For example, the compiler will
> catch typos in class names.
>
Thanks for this suggestion. This looks fairly clean except that the space is
allocated at the beginning. This may not be a big deal in some cases. In the
other way, you allocate space and insert in the dictionary only when needed.
Also, eventually i need the real object instances inserted in the
dictionary.
-mohan
-mohan
>
> Cheers,
> Ken
>
>
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