Question

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What's wrong with Delphi's “with”

I am have a problem debugging code that uses a ‘WITH’ statement in BDS 2006 The debugger will not show the values of the variables with in a class or record. Am I doing something wrong or does BDS 2006 have a bug ?

type   TNumber = class       Num: Integer;   end;  implementation  {$R *.dfm}  var    MyNumber: TNumber;  procedure TForm2.FormCreate(Sender: TObject); begin    MyNumber := TNumber.Create;    MyNumber.Num := 10;   /// MyNumber.Num Can be seen with debugger    with  MyNumber do    begin      Num := Num +1 ;           /// Num is not seen by the  debugger      MyNumber.Num := Num +1 ;  /// MyNumber.Num is seen but Num is not seen by the  debugger    end; end; 

EDIT:

Sure one can use the full name of the variable But things become very messy if you have a complex structure with more than one level

Answer 1

With is considered by many one of those language features that falls into the ‘just because you have it doesn’t mean you have to use it’ category. There are very few occasions where I’d give it house-room – I’ve found one or two cases where it’s use is essential when using extremely complex multi-level structures where the compiler doesn’t do quite as you’d expect without it and it is easier to include, but in 10 years of coding Delphi I think these could be counted on the fingers of one hand.

It does tend to get used rather a lot in examples as the code certainly looks cleaner, but in practice the maintenance impact of figuring out if a variable is simple or part of a structure when reviewing code you didn’t write or haven’t used for a period easily outweighs that. The known issues with the debugger on every version of Delphi I’ve ever used is the clincher.