undo prepareWithInvocationTarget KVC

• Steven Spencer undo prepareWithInvocationTarget KVC Jul 03 2005, 02:18
  Hello,
  
  In my project, the following line of code works :
  
  [[[self undoManager] prepareWithInvocationTarget:[myArray
  objectAtIndex:0]] setTarget:@"Hello"];
  
      myArray is an NSArray containing instances of class myObj.
      Class myObj has two methods :
  
      - (void)setTarget:(NSString *)aString;
      - (NSString *)target;
  
      myArray is bound to a tableview column.
  
  When I replace the line with :
  
  [[[self undoManager] prepareWithInvocationTarget:[myArray
  objectAtIndex:0]] setValue:@"Hello" forKey:@"target"];
  
  the following errors can occur :
  
  sigsev,
  sigbus,
  [<NSCFString 0x33d950> valueForUndefinedKey:]: this class is not key
  value coding-compliant for the key target.
  
  Does anyone know why it's looking for the key "target" in a string
  instead of a myObj instance ?
  
  The error occurs after the prepareWithInvocationTarget code has run,
  when a new row is selected in the tableview.
  
  Thanks for any insight.
  
    - Steve Spencer
• Steven Spencer Re: undo prepareWithInvocationTarget KVC Jul 03 2005, 15:38
  I've found a solution :
  
          myObj *mx = [myArray objectAtIndex:0];
  
          SEL theSelector = @selector(setValue:forKeyPath:);
          NSMethodSignature *sig = [mx
  methodSignatureForSelector:theSelector];
          NSInvocation *inv = [NSInvocation
  invocationWithMethodSignature:sig];
          [inv setSelector:theSelector];
          [inv setTarget:mx];
  
          NSString *h = @"Hello";
          NSString *t = @"target";
  
          //Note: indices 0 and 1 are reserved for self and _cmd
          [inv setArgument:&h atIndex:2];
          [inv setArgument:&t atIndex:3];
  
          [[self undoManager] prepareWithInvocationTarget:mx];
          [[self undoManager] forwardInvocation:inv];
  
    - Steve Spencer
  
  On 3 Jul 2005, at 01:18, Steven Spencer wrote:
  
  

  > Hello,
  >
  > In my project, the following line of code works :
  >
  > [[[self undoManager] prepareWithInvocationTarget:[myArray
  > objectAtIndex:0]] setTarget:@"Hello"];
  >
  > myArray is an NSArray containing instances of class myObj.
  > Class myObj has two methods :
  >
  > - (void)setTarget:(NSString *)aString;
  > - (NSString *)target;
  >
  > myArray is bound to a tableview column.
  >
  >
  > When I replace the line with :
  >
  > [[[self undoManager] prepareWithInvocationTarget:[myArray
  > objectAtIndex:0]] setValue:@"Hello" forKey:@"target"];
  >
  > the following errors can occur :
  >
  > sigsev,
  > sigbus,
  > [<NSCFString 0x33d950> valueForUndefinedKey:]: this class is not
  > key value coding-compliant for the key target.
  >
  > Does anyone know why it's looking for the key "target" in a string
  > instead of a myObj instance ?
  >
  >
  > The error occurs after the prepareWithInvocationTarget code has
  > run, when a new row is selected in the tableview.
  >
  > Thanks for any insight.
  >
  > - Steve Spencer
  >