More flexible "performselector"

I want to invoke a selector of a method that has the usual nserror ** argument:

 -(  Int  )  Getitemssince  :(  Nsdate     *)  When  Dataselector  :(  Sel  )  Getdataselector Error  :(  Nserror  **)  Outerror  { 
  Nsarray     *  Data  =     Nil  ;  
  If  ([  Service respondstoselector  :  Getdataselector  ])     {  
Data  =    [  Service performselector  :  Getdataselector withobject  :  When  Withobject  :  Outerror  ];  
  // Etc. 

... Which the compiler doesn't like:

Warning:Passing argument3Of'Your mselector: withobject :' FromIncompatible pointer type

 
¥ ¥ ¥
 

 
Check out nsinvocation, which gives you a more flexible way to "performselector ".
 

 If     ([  Service respondstoselector  :  Getdataselector ])     {  
  Nsarray     *  Data  ;  
  Nsinvocation     *  Invocation  =     [  Nsinvocation  Invocationwithmethodsignature  : 
  [  Service methodsignatureforselector  :  Getdataselector  ];  
  [  Invocation settarget  :  Delegate  ];  
  [  Invocation setselector  :  Getdataselector  ];  
 // Note: indexes 0 and 1 correspond to the implicit arguments self and _ cmd,  
  // Which are set using settarget and setselector.  
  [  Invocation setargument  :  When  Atindex  :  2  ];   
  [  Invocation setargument  :  Outerror atindex  : 3  ];  
  [  Invocation invoke  ];  
  [  Invocation getreturnvalue  :&  Data  ];  
  } 

 
//////////////////////////////////////// ////
 

 
Perform selector calls more than two parameters
 

 
You can also put all the parameters in the dictionary, such as nsnotification or nstimer userinfo.