Changing classes created with loadNibNamed

Question

I am trying to change the class of objects created using the tip with the iPhone SDK.

The reason for this is; I still don't know what the class I want the nib object to be (although they will have the same superclass of the UIView class), and I don't want to create a different thread for each case - since .nib will be the same for everyone except class of one object.

I was successful with several methods, but either had some knocking on effects, or was not sure how safe the methods I used were:

Method 1: override alloc in the superclass and set the variable c to the class I need:

+ (id) alloc {
 if (theClassIWant) {
  id object = [theClassIWant allocWithZone:NSDefaultMallocZone()]; 
  theClassIWant = nil;
  return object;
 }
 return [BaseClass allocWithZone:NSDefaultMallocZone()];
}

this works well, and I assume that it is “reasonably” safe, although if it has zero with the correct class as the class identifier in Nib, or I subclasses myself (without setting theClassIWant), an object is created in the base class. I also don't like the idea of ​​overriding alloc ...

Method 2: use object_setClass (self, theClassIWant) in initWithCoder (before calling initWithCoder in the superclass):

- (id) initWithCoder:(NSCoder *)aDecoder {
 if (theClassIWant) {

  // the framework doesn't like this:
  //[self release];  
  //self = [theClassIWant alloc];

  // whoa now! 
  object_setClass(self,theClassIWant);

  theClassIWant = nil;
  return [self initWithCoder:aDecoder];
 }

 if (self = [super initWithCoder:aDecoder]) {
           ...

• this also works well, but not all subclasses will necessarily be the same size as the superclass, so this can be very dangerous! To combat this, I tried to free and redistribute the correct type in initWithCoder, but I got the following error from the framework:

  "This encoder requires replaced objects to be returned from initWithCoder:"

I don’t understand what that means! I am replacing an object in initWithCoder ...

!

Answer 1

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