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  1. System.Rtti contains a lesser known, but powerful class TMethodImplementation, which is basically hidden and used in TVirtualMethodInterceptor. Outside this use, it cannot be created directly and it can only be accessed by TRttiMethod.CreateImplementation. I recently discovered that Spring4d extends its use through a helper for TRttiInvokableType, so it can be used with standalone procedures and functions as well as with events. Here is a small console app showing how it can be used: program MethodImplementationTest; {$APPTYPE CONSOLE} {$R *.res} uses System.SysUtils, System.TypInfo, System.Rtti, Spring; type TSimpleProc = function(I: Integer): Integer; procedure ImplCallback(UserData: Pointer; const Args: TArray<TValue>; out Result: TValue); begin WriteLn('From Implementation'); Result := Args[0].AsInteger * 2; end; var Proc: TSimpleProc; begin ReportMemoryLeaksOnShutdown := True; try var RTTIContext := TRttiContext.Create; var RTTIType := RTTIContext.GetType(TypeInfo(TSimpleProc)); var ProcImplementation := (RTTIType as TRttiInvokableType).CreateImplementation(nil, ImplCallback); Proc := TSimpleProc(ProcImplementation.CodeAddress); WriteLn(Proc(2)); ProcImplementation.Free; except on E: Exception do Writeln(E.ClassName, ': ', E.Message); end; ReadLn; end. Output: From Implementation 4 Simple and easy. Spring4D is full of gems. I wish the above functionality was part of the standard library. I can think of many uses: Python4Delphi contains a unit MethodCallback which uses complex assembly to convert methods into stubs that can be used with external C libraries. It could be rewritten using TMethodImplementation, without assembly code. Also in Python4Delphi, the implementation of Delphi events using python code could be very much simplified and generalized using TMethodImplementation. You can create Delphi functions, procedures and methods, event handlers on the fly that are implemented by python code. Similarly functionality can be provided with other scripting languages.
  2. Using the GroupBy method, I wonder if it possible to "imbricate" GroupBy in Spring4D to generate a "two levels" tree in one pass Some sort of: var GByData : IEnumerable<IGrouping<string,TVariable>>; GByData2 : IEnumerable<IGrouping<string,TVariable>>; begin GByData := TEnumerable.GroupBy<TVariable, string>(IEnumTV, function (const ASVar: TVariable): string begin Result := ASVar.AppName; end); GByData2 := TEnumerable.GroupBy<TVariable, string>(GByData, function (const ASVar: TVariable): string begin Result := ASVar.PrjName; end); end; Thanks a lot, Eddy
  3. Hi, In testing the function TEnumerable.GroupBy<T, TKey>(const source: IEnumerable<T>; const keySelector: Func<T, TKey>): IEnumerable<IGrouping<TKey, T>> in Spring Version Dev 2021/03/24 and Version 1.2.4, I find that a noticeable difference is present if I am not mistaken. The 3rd listbox (in the associated example) does not have the elements in the same order (and is even incorrect in the dev version- maybe because defered execution) depending on the version. In version 1.2.4, the order is "stable", which is an interesting property from my point of view. Will the behavior of the Dev version be the one adopted in the next version? Thanks, Eddy ITreeData.zip
  4. I have problem with one factory. definition TSQLDataSuiteWorkerMethod = procedure(const aDataSuite : ISQLDataSuite) of object; TSQLDataSuite = class(TInterfacedObject, ISQLDataSuite) [...] public constructor Create(const aTableName: RawByteString; const aSQLKind: TModifyingSQLKind; const aProcessSQL : Boolean = True; const aBeforeWorkerMethod: TSQLDataSuiteWorkerMethod = nil; const aAfterWorkerMethod: TSQLDataSuiteWorkerMethod = nil); reintroduce; end; {$M+} TSQLDataSuiteFactory = reference to function(const aTableName: RawByteString; const aSQLKind: TModifyingSQLKind; const aProcessSQL : Boolean = True; const aBeforeWorkerMethod: TSQLDataSuiteWorkerMethod = nil; const aAfterWorkerMethod: TSQLDataSuiteWorkerMethod = nil): ISQLDataSuite; {$M-} container registration aContainer.RegisterType<TSQLDataSuite>.Implements<ISQLDataSuite>; aContainer.RegisterFactory<TSQLDataSuiteFactory>; resolve in code: fSQLDataSuiteFactory : TSQLDataSuiteFactory; var Data: ISQLDataSuite; begin Data := fSQLDataSuiteFactory('TableName', TModifyingSQLKind.SQLInsert, True, nil, nil); And after last l get exception from Spring4D: Unsatisfied constructor on TSQLDataSuite What have I forgotten? I use in the program dozens of factories, classes and interfaces, all based on the spring container, everything works correctly, only this case I cannot understand. ps. maybe it's worth opening a subforum for Spring4D?
  5. Larry Hengen

    Spring4D Persistence

    I am looking for the best place to ask questions regarding Spring4D's persistence functionality known as Marshmellow. I am starting a SQLLite3 project and would like to know how Spring4D maps the specified types in the Column attribute to SQLLite types. I also have a lazily loaded list owned by another object, call it Parent. When a Parent is created and saved to the database if I then try to add a Child object to the lazily loaded list, I get an error that: 'No delegate has been assigned'. My code looks like the examples I see in the test projects. What am I doing wrong?
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