"Possible unsafe operation" with Nullable<TDateTime>

[stuartc...@gmail.com]

Hi,

I'm new to Spring4D and I'm trying code shown

// minimal viable reproducable test case....

var

  NDate: Nullable<TDateTime>;

  aDate, aTime: TDateTime;

begin

  try

    aDate := EncodeDate(2020,06,02);

    aTime := EncodeTime(11, 5, 0, 0);

    NDate := aDate;

    NDate := NDate.Value + aTime; // compiler warning

The compiler  (10.3)  is giving me:

[dcc32 Warning] Project31.dpr(19): W1000 Symbol '&op_Implicit' is deprecated: 'Possible unsafe operation involving implicit Variant conversion - use explicit cast'

My company is tough on compiler warnings so I'd like to know a) if I'm doing that correctly and b) if so, should I remove that compiler warning? 

Thanks in advance.

PS The original code is getting dates/times from a TDataset so I need to conditionally add the time value if the field is not null.

[Stefan Glienke]

Looks like a compiler glitch where it choses the wrong overload and turns the result of the addition into a Variant to pass that to the nullable.

Go to Spring.inc and disable {$DEFINE UNSAFE_NULLABLE} to completely remove these unsafe operators (they were in 1.2 for backwards compatibility and exactly for that reason raised that warning)

When you do so the compiler is forced to use the proper implicit operator overload which takes a TDateTime.

[Stuart Clennett]

Thanks Stefan

[Toni Grabmayr]

Hi,

I use Nullable<Double> and run into the same warning. When I disable  {$DEFINE UNSAFE_NULLABLE}  in Spring.inc then a explicit MyVar := NULL is not possible any more; I get at runtime an error msg that Variant-Value couldn't be assigned to Double. When I activate the DEFINE it works again. However, I tried then to switch the GIT-branch to <developer> as I read that there were some patches to that - no success as well setting NULL to this kind of variable.

Any ideas, hints, practical advice?

Thanks in advance.

Toni

(Delphi Rio 10.3.3, Win 10/64, 32-bit)

[Philipp Schäfer]

Hi,

newer version of Nullable<T> should be assigned to nil and no longer NULL as far as I am aware.

Hope that helps.

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[Toni Grabmayr]

Hi, 

thanks for the fast reply! So setting MyVar := DBField.Value (Variant, NULL) not works any more(?) and this should be replaced by DBField.AsFloat. I'll have to test that. I wanted to use Nullable<T> as I in deed need to reflect if a value (even 0) was entered or not,,,

thx