mORMot Open Source

testgary

Member

Registered: 2025-02-06

Posts: 27

VariantToDouble

procedure TMvcApplication.RatingConvert(const Value: variant; out Result: variant);
var
  D: double = 0;
  B: boolean;
begin
  SetVariantNull(Result);

  // Normal
  OutputDebugString(PChar(VariantToString(Value)));
  VariantToDouble(variant(20.6170212765957), D); 
  D := Value;

  // Abnormal
  B := VariantToDouble(Value, D); 
end;

Value := 20.6170212765957

I don't know if it's my problem or someone else's problem

Last edited by testgary (2025-06-10 06:13:27)

ab

Administrator

From: France

Registered: 2010-06-21

Posts: 15,069

Website

Re: VariantToDouble

Sorry, I don't get what is going on in your code, and what "abnormal" is?

testgary

Member

Registered: 2025-02-06

Posts: 27

Re: VariantToDouble

Sorry, I don't get what is going on in your code, and what "abnormal" is?

It's not an error, but the data cannot be retrieved if the value is in a format like 20.6170212765957. This is because MongoDB's Double type stores numbers with such long decimal precision.

This is a method I defined using RegisterExpressionHelpers.

 (TMvcRunOnRestServer(fMainRunner).Views as TMvcViewsMustache).
  RegisterExpressionHelpers(['RatingConvert'], [@RatingConvert]); 

ab

Administrator

From: France

Registered: 2010-06-21

Posts: 15,069

Website

Re: VariantToDouble

I still don't get it, sorry.

What is the BSON type?
betFloat or perhaps betDecimal128 ?

testgary

Member

Registered: 2025-02-06

Posts: 27

Re: VariantToDouble

procedure TMvcApplication.DoText(const Value: variant; out Result: variant);
var
  D: double = 0;
  B: Boolean;
begin
  // "D" does not receive a valid result, but integers do
  B := VariantToDouble(Value, D);
end;      

procedure TMvcApplication.Start(aRestModel: TRest; aInterface: PRttiInfo);
begin
  (TMvcRunOnRestServer(fMainRunner).Views as TMvcViewsMustache).
  RegisterExpressionHelpers(['DoText'], [@DoText]);  
end;  

// Frontend template snippet
{{DoText 20.6170212765957}}

ab

Administrator

From: France

Registered: 2010-06-21

Posts: 15,069

Website

Re: VariantToDouble

I can't reproduce it.

Please debug a little to find out what is wrong.

Normally, TSynMustacheContext.ProcessHelper() should properly set the value using JsonToVariantInPlace(JSON_FAST_FLOAT).