Re: Constructing class names dynamically
Re: Constructing class names dynamically
- Subject: Re: Constructing class names dynamically
- From: "Adam Venturella" <email@hidden>
- Date: Wed, 14 Jan 2009 06:46:23 -0800
The output is the same, but there is also:
#import <objc/runtime.h>
objc_getClass([myString UTF8String]);
I am going to guess that NSClassFromString(myString) is probably using
objc_getClass(), maybe not. I didn't know NSClassFromString existed
though, so I am switching to that instead of using the runtime.h
function.
On Tue, Jan 13, 2009 at 8:45 PM, Mohan Parthasarathy <email@hidden> wrote:
> 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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