IsNullOrWhiteSpace???

[Ian Branch 128]

Hi Team,

I am trying to figure out the wierd usage of the TStringHelper IsNullOrWhiteSpace.

I have seen this  as   "if ''.IsNullOrWhiteSpace(MyString) then",  and this   "MyString.IsNullOrWhiteSpace(MyString) then".

Are both correct?  Why the confusing construct?

From the class definition, "class function IsNullOrWhiteSpace(const Value: string): Boolean; static;" I had expected to be able to simply do a more readable "if IsNullOrWhiteSpace(MyString) then ".

 

Regards & TIA,

Ian

Edited March 25, 2023 by Ian Branch

[Attila Kovacs 631]

Use it as TStringHelper.IsNullOrWhiteSpace() in order to avoid misunderstandings.

Your examples are just the side effects of this record helper on the string type.

 

[Ian Branch 128]

Hi Attila,

I tried that with this   "if TStringHelper.IsNullOrWhiteSpace('sMyString') then"

but get an 'E2018 Record, object or class type required' error.

[Attila Kovacs 631]

Wow, well, a shitty design.

[Ian Branch 128]

I've just settled for   "if Trim(MyString) = '' then"

[programmerdelphi2k 237]

if you see in "source code", you should can ignored this, in better choice!

Quote

class function TStringHelper.IsNullOrWhiteSpace(const Value: string): Boolean;
begin
  Result := Value.Trim.Length = 0;
end;

better would be, directly  "if LVar.Trim.Length = 0 then ...", no pain, no gain.... no trap!

Edited March 26, 2023 by programmerdelphi2k

[Ian Branch 128]

All good.

 

Tks Guys.

[David Heffernan 2354]

Surely it's 

 

If string.IsNullOrWhiteSpace(someStr) then 

 

like in .net

[david berneda 19]

I wish a compiler option to warn when calling class methods on instances instead of using the class type.

 

Another one, hint when methods can be safely converted to class or class static.

 

 

[David Schwartz 430]

You probably don't need the class name in front.

 

and isn't this form also acceptable: myString.IsNullOrWhiteSpace

 

 

[David Heffernan 2354]

1 hour ago, David Schwartz said:

You probably don't need the class name in front.

 

What is the subject of the method then? 

 

1 hour ago, David Schwartz said:

and isn't this form also acceptable: myString.IsNullOrWhiteSpace

What argument are you going to pass, and what purpose does myString serve? 

[Fr0sT.Brutal 900]

I'd too expect it to be instance method. No string in Delphi could be null in fact so there's no sense in static class method. Probably they simple copypasted it from .Net which has nulls and thus such function couldn't be an instance method?

Edited March 27, 2023 by Fr0sT.Brutal

[David Heffernan 2354]

It doesn't much matter what anybody expects the design to be. Too late for that now. 

 

Given that it takes the string as an argument, and it's a static class method, I think it's safe to conclude that you don't call it as an instance method. Wouldn't it just be better if the language forced you to call it on a class? 

[Lars Fosdal 1793]

It could have had a parameterless overload that could be used for the instance.

  if string.IsNullOrWhiteSpace(s)
  then Writeln('Yup');

  if s.IsNullOrWhiteSpace
  then Writeln('Yup');

As it is now, only the first construct is supported.

[Lars Fosdal 1793]

There is a lot of strange code in that helper.

Have a look at function IsEmpty, which compares the string to a record local const Empty - when the unit already has a global constant EmptyStr. Go figure.