Re: Error on ActiveGraph class application

[Frank Lin]

HI, Manor,
  Thanks for your hints.  I have fixed it according to your correction.

Frank

> 
> Hi Frank,
> 
> In Objective-C declaring a variable to be of a particular class does not 
> automatically generate an instance of that class in the variable. In other
> words the variable is initialized to nil.
> 
> Therefore in your code, is initialized to nil.
> 
>  --------
>   BLTGraph *mflowGraph;
>   GraphElement *materialElement;
>   ActiveGraph  *mflowGrapher;
> 
>   StatusM *statusM;
> 
> And therefore the statement:
> 
>   [mflowGrapher setDataFeed: statusM]; 
> 
> is setting the DataFeed on mflowGrapher to nil. The grapher therefore 
> complains since it does not have a valid feed object.
> 
> You would therefore need to create the object statusM before giving it
> as a dataFeed to the grapher by (for example) inserting the statement:
> 
>   statusM = [StatusM create: globalZone] ;
>   
> between the declaration of statusM and its use...
> 
> Regards,
> 
> Manor.
>