I need get property name as string from object class. It is possible in Delphi?
I need property transfer as argument of method and get property name as string. I don't want use property name as argument because the compiler does not catch error when name of property is changed in class.
type
TMyClass = class
private
fField: some_type;
public
property Field:some_type read fField;
end;
function GetPropertyName(arg: ??):string
begin
Result := arg.PropertyName; // here I need get property name form transfer type
end;
var
obj: TMyClass;
name: string;
begin
name := GetPropertyName(obj.Field);
end;
To clarify, as discussed in comments, I'm looking for a direct equivalent to the C# nameof function.
From the comments you make it clear that you are looking for a Delphi equivalent to the C# nameof function.
No such equivalent exists in Delphi, and the language does not have facilities for you to create it yourself. Instead you will need to name the method as a string literal in code.
Related
as my post describes it, I'd like to create an UTIL class with a never_both function.
class
UTIL
create
default_create
feature -- could be in class BOOLEAN
double_implies, reversible_implies, never_both (a, b: BOOLEAN): BOOLEAN
-- Into boolean class with never_with
do
if a and b then
Result := False
else
Result := True
end
end
end
When I use it
invariant
never_both: {UTIL}.never_both (attached last_error, attached last_success_message)
the compiler complains about a VUNO error
never_both used in the non-object call is not a class feature.
I saw 2 notations about objects creating
- {UTIL}.never_both (a, b)
- ({UTIL}).never_both (a, b)
Whats the difference between them?
How to create an application wide (could be even world wide once if you want!) object for the use of this UTIL if possible in Eiffel?!
I know this is a TUPLE of questions so I put them in Bold
If you want to use a feature without creating the corresponding object, it should be marked as a class feature. This is done in the feature postcondition with the same keyword:
foo ...
do
...
ensure
instance_free: class
...
end
After that, the feature can be used in an objectless call {BAR}.foo ....
The notation ({BAR}).qux does not denote an objectless call. It is an object call on the target object of type TYPE [BAR]. The object describes the type BAR.
Recently at my company we tried to use DUnitX with all it's blessings to test classes we wrote. Since those classes reflect entities in database all fields have to accept null values as well as specific type (e. g. Integer or string).
Since spring4d already have those we tried to use them:
INaleznosc = interface
['{D5D6C901-3DB9-4EC2-8070-EB0BEDBC7B06}']
function DajPodstawaVAT(): TNullableCurrency;
property PodstawaVAT: TNullableCurrency read DajPodstawaVAT;
end;
TNaleznosc = class(TInterfacedObject, INaleznosc)
strict private
FId: TNullableInt64;
FPodstawaVAT: Currency;
function TNaleznosc.DajPodstawaVAT(): TNullableCurrency;
published
property PodstawaVAT: TNullableCurrency read DajPodstawaVAT;
end;
INaleznoscFunkcje = interface
['{509288AB-110A-4A52-BE93-3723E5725F4B}']
function DajPodstawaVAT(pID: TNullableInt64): TNullableCurrency;
end;
function TNaleznosc.DajPodstawaVAT(): TNullableCurrency;
begin
FPodstawaVAT := FFunkcje.DajPodstawaVAT(FId);
end;
procedure TTestNaleznosc.PodstawaVATGetterNieWywolujefunkcji();
var
funkcjeNaleznosc: TMock<INaleznoscFunkcje>;
klasa: INaleznosc;
id: TNullableInteger;
begin
//initialize tested elements
funkcjeNaleznosc := TMock<INaleznoscFunkcje>.Create();
id := 15;
klasa := TNaleznosc.Create(funkcjeNaleznosc, id, zmienne);
//setup expected behaviour from mock
funkcjeNaleznosc.Setup.WillReturn(2).When.DajPodstawaVAT(id);
funkcjeNaleznosc.Setup.Expect.Once.When.DajPodstawaVAT(id);
//this triggers getter
klasa.PodstawaVAT;
end;
When this code is executed we get AV exception First chance exception at $00000000. Exception class $C0000005 with message 'access violation at 0x00000000: access of address 0x00000000'. Process Tests.exe (6556).
Eventually we narrowed this issue down to Move procedure in System.Rtti unit, TValueDataImpl.ExtractRawDataNoCopy function:
when Length(FData) is less or equal to 8 it works fine
when Length(FData) is between 9 and 32 at line 5905 of System unit (FISTP QWORD PTR [EDX+8] {Save Second 8}) whole call stack disappears beside two lines (we are not sure whether it's relevant or not, but it doesn't look like good sign) and after getting to topmost function (according to call stack) we get error.
Call stack before "saving second 8"
Call stack after "saving second 8"
Is it our fault or is it some issue with system/spring/dunitx units? How can we use nullable types and tests at the same time?
I am not sure if Delphi Mocks has a generic type parameter on its WillReturn method but if so then pass TNullableCurrency there - otherwise the compiler will infer the type from the parameter 2 you are passing and obviously internally it fails to put that into the TNullableCurrency it should return.
If it does not and only allows TValue then you need to pass one that contains a TNullableCurrency and not 2 which it would by using its implicit operator like so: TValue.From<TNullableCurrency>(2)
Furthermore I am not sure if they did fix the code in the SameValue routine in Delphi Mocks when the value to be compared is a record (as TNullableCurrency is)
Edit: no, they did not - see https://github.com/VSoftTechnologies/Delphi-Mocks/issues/39
You might want to consider giving Spring4D mocks a try which should be able to handle nullables.
Is it possible to use interfaces with objects in plsql?
For example say I have a bunch of objects and want to sort them by date with a generic function. Could I have something like the following?
create or replace interface DateInterface
(
member function get_date return date
)
/
create or replace type TypeA implements DateInterface
(
my_date date,
member function get_date return date
)
/
create or replace type body TypeA is
member function get_date return date is
begin
return my_date;
end;
end;
/
create or replace type dateTable as table of DateInterface;
/
function EarliestDate (dates dateTable) returns date is
l_earliestDate date;
begin
l_earliestDate := dates(1);
for i in dates.first .. dates.last
loop
if l_earliestDate.get_date > dates(i).get_date then
l_earliestDate := dates(i);
end if;
end loop;
return l_earliestDate;
end;
I know I could have them inherit a class, but is there anything for doing this with an interface which would be more flexible?
Oracle supports interfacing external sources like Java and C languages within its procedures and functions using the LANGUAGE clause in them. Implement the date sorting logic of the objects in a procedure or a function and interface with other programming languages.
For reference, see Oracle's documentation
I'm late to the party but Oracle has sort of OO support now in PLSQL:
https://docs.oracle.com/en/database/oracle/oracle-database/18/adobj/inheritance-in-sql-object-types.html#GUID-A5FE7A3B-7C1C-430A-8095-76AE955119C9
You have inheritance etc. with that. So you could do sort of an interface for PLSQL Object Type Objects
But it comes with problems. Eg. storing in tables.
See https://oracle-base.com/articles/8i/object-types
Following on from my question Inno Setup disable component selection when a specific component is selected, I think there may be a way to get this to work without the problem of checked states set in code being permanent (though use of the Checked property) by instead using:
function CheckItem(const Index: Integer; const AOperation: TCheckItemOperation): Boolean;
in TNewCheckListBox, however I am having trouble getting the syntax correct. I am trying:
CheckItem(CompIndexSync, coUncheck) := Checked[CompIndexClient];
where the CompIndexes are constants assigned to the indexes for the component values. I get an Identifier Expected error at compile. Can someone advise how to correctly use this function and what I am doing wrong?
The CheckItem member of the TNewCheckListBox class is a method of type function which updates the checked state by the AOperation operation and returns True if any changes were made to the state of the item at Index, or any of its children. Here is its prototype (source):
function TNewCheckListBox.CheckItem(const Index: Integer;
const AOperation: TCheckItemOperation): Boolean;
The problem was that you were trying to assign a value to the function result. That's not what you can do in Pascal language in general.
What you want to do with the item(s) is passed by the AOperation parameter. In pseudocode e.g.:
var
CheckList: TNewCheckListBox;
Operation: TCheckItemOperation;
begin
...
if ShouldCheck then
Operation := coCheck
else
Operation := coUncheck;
if CheckList.CheckItem(ItemIndex, Operation) then
MsgBox('An item has changed its state.', mbInformation, MB_OK);
end;
I have the following situation.
We develop in DelphiXE.
We are putting the majority of our functions in a DATAMODULE.
function1 (database, transaction, paramInteger) : float
for example
function1 take parameters database (TIBDATABASE), the transaction TIBTRANSACTIOn and aditiona parameter integer. and return a float
function GetLastPretAch(DIBase : TIBDatabase; Tran : TIBTransaction; const aID : Integer) : Double;
var workQuery : TIBQuery;
begin
try
workQuery := TIBQuery.Create(Application);
try
workQuery.Close;
workQuery.Database := DIBase;
workQuery.Transaction := Tran;
workQuery.SQL.Clear;
workQuery.SQL.Add('SELECT * FROM GETLASTPRETACH(-1, :AARTNR)');
workQuery.ParamByName('AARTNR').AsInteger := aID;
workQuery.Open;
Result := workQuery.FieldByName('LASTPRET').AsFloat;
except
on e : Exception do begin
raise EMagisterException.Create(TranslateIbError(e));
end;
end;
finally
FreeAndNil(workQuery);
end;
end;
Now I want to use this functions from a thread. is this thread safe?
inside execute procedure like
ID := GetLastPretAch(database, transaction, 1);
is or not thread safe?
The answer to your question is Yes, you can use that function from inside a worker thread's execute procedure. You might want to consider refining your SQL to only SELECT the field LASTPRET instead of SELECT *.
For an extended discussion on what "thread safe" means refer to this SO question
What does threadsafe mean?
Looks like you're using IBX Components which, the last time I looked were most definitely NOT thread-safe. If you switched to a data access layer that was thread-safe, you should be fine with that code. FYI UIB (Unified Interbase components) are thread-safe.