[Mono-list] Suggestion: warning "member variable not initialized"

[Thong (Tum) Nguyen]

Members are implicitly initialized to 0 or null so they do have a
meaning even if you don't explicitly initialize them...

^Tum


> -----Original Message-----
> From: mono-list-admin@lists.ximian.com [mailto:mono-list-
> admin@lists.ximian.com] On Behalf Of Maurizio Colucci
> Sent: Sunday, 8 June 2003 12:50 a.m.
> To: mono-list
> Subject: [Mono-list] Suggestion: warning "member variable not
initialized"
> 
> Hi,
> 
> Currently the Microsoft C# compiler gives an error if you forget to
> initialize a readonly member variable (this can be done either in the
> contructor or in the declaration itself.)
> 
> I already posted a wish for mcs about that, but:
> 
> What about extending this behavior to non-readonly member-variables?
> (Maybe a warning instead of an error?)
> 
> RATIONALE:
> 
> I cannot think of a case where not initializing a member variable (in
> the constructor or at declaration time) makes sense. So we would catch
> a frequent semantic error without any drawback...
> 
> Someone could reply that there ARE indeed some cases when you don't
> know an appropriate value for a member variable when the constructor
> is called. Maybe the user must initialize it explicitely, after
> construction.
> 
> e.g.
> 
> class C{
>   private int member_var;
> 
>   public C(){
>     // I don't yet know how to initialize member_var. Only the
>     // user can do that, via the Init method.
>   }
> 
>   public void Init(int m){
>     member_var=m;
>   }
> 
> }
> 
> But, on the other hand, the above is bad design:
> 
> If member_var is not always meaningful across the lifetime of class C,
> then member_var should NOT have been declared as a member of C, in the
> first place. In other words, C is a state machine with two states:
> Initialized and NotInitialized, such that member_var only makes sense
> in the Initialized state, and not in the other one.
> 
> Good design:
> 
> class C{
> 
>   private abstract class State{}
>   private class Initialized: State{
>     	public int member_var; // this variable only makes sense
>                         // when C is in the Initialized state!
>                         // therefore it is declared here,
>                         // not inside C.
>         public Initialized(int m){
>              member_var = m;
>         }
>   }
> 
>   private class NotInitialized: State{}
> 
>   private int state = new NotInitialized();
> 
>   public void Init(int m){
>     state = new Initialized(m);
>   }
> 
> }
> 
> 
> In this latter example, member_var DOES NOT EXIST when it does make
> sense. This avoid the risk that someone reads/writes it when it makes
> no sense!
> 
> In the former case, there is a time when member_var exists but does
> not make sense (and is not initialized). Error prone.
> 
> So by raising an error in the former case we would enforce good
> design.
> 
> Any comments?
> 
> 
> 
> 
> 
> 
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