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Found 6 results

  1. Diego Simonini

    Code Formatter and generics

    Hi, given this configuration for spacing math operators sometimes the formatter formats generics declarations with spaces (especially in methods parameters) using 1.3.18 build 3342 How to fix? Thanks
  2. Hi there, I have a component like this: TCustomEdit<T: record> = class; TOnValidate<T: record> = function (ASender: TCustomEdit<T>; AValue: T): Boolean of object; TCustomEdit<T: record> = class(TEdit) private fOnValidate: TOnValidate<T>; // code here published property OnValidate: TOnValidate<T> read fOnValidate write fOnValidate; end; TIntEdit = class(TCustomEdit<Integer>) // code here end; The code compiles and TIntEdit registers without any complaints. But, when I want to drop the component onto a form, Delphi crashes with AV. What I am missing? I tested it on Delphi XE4 and Delphi 10.4 CE. It's a bug, feature of just "by design"? @Stefan Glienke, will you help? Anyone?
  3. if I pass set type into MyGenericMethod<T: record> - I get compile type error [dcc32 Error] Project2.dpr(28): E2512 Type parameter 'T' must be a non-nullable value type Is it OK or compiler bug ?? program Project2; {$APPTYPE CONSOLE} {$R *.res} uses System.SysUtils; type TMyEnum = (en1); TMySet = set of TMyEnum; type TTestClass = class class procedure MyGenericMethod<T: record>; end; class procedure TTestClass.MyGenericMethod<T>; begin // end; begin try { TODO -oUser -cConsole Main : Insert code here } TTestClass.MyGenericMethod<TMySet>(); except on E: Exception do Writeln(E.ClassName, ': ', E.Message); end; end.
  4. I have a section of code where I need to modify the top record on a stack. This code is supposed to be highly performant, so I would like to optimize it as much as possible. I would like to get the top record of the stack without popping and pushing it. The record is somewhat complex, so copying the data back and forth to a temporary record is silly. A sample program is below type TMyRec=record s:string; end; PMyRec=^TMyrec; var stk:TStack<TMyRec>; rec:TMyRec; prec:pMyRec; begin stk:=TStack<TMyRec>.Create; rec.s:='Hello'; stk.push(rec); prec:=@stk.Peek; // get error “variable required” prec.s:=’Goodbye’; stk.Free; end; Seems like @stk.Peek is returning the address to the Peek method, not the pointer of the element being returned by the peek method. I have tried casting in various ways but it never compiles properly. Any ideas?
  5. Hello all, I'm stumbling on an unexpected generics-related problem here (Delphi XE). I'm trying to implement a backward-running enumerator for a generic tList<T>. I believe I did everything correctly but still the enumerator runs forward unless I make a modification that really shouldn't be necessary. TYPE tListEnumReversed<T> = CLASS(tEnumerator<T>) PROTECTED fowner: tlist<T>; fListIndex: integer; FUNCTION DoGetCurrent: T; OVERRIDE; FUNCTION DoMoveNext: Boolean; OVERRIDE; PUBLIC CONSTRUCTOR Create(owner: tlist<T>); END; tListReversed<T> = CLASS(tlist<T>) PROTECTED FUNCTION DoGetEnumerator: tEnumerator<T>; OVERRIDE; END; CONSTRUCTOR tListEnumReversed<T>.Create(owner: tlist<T>); BEGIN fowner := owner; fListIndex := owner.count; END; FUNCTION tListEnumReversed<T>.DoGetCurrent: T; BEGIN Result := fowner[fListIndex]; END; FUNCTION tListEnumReversed<T>.DoMoveNext: Boolean; BEGIN Result := fListIndex > 0; IF Result THEN Dec(fListIndex); END; FUNCTION tListReversed<T>.DoGetEnumerator: tEnumerator<T>; BEGIN Result := tListEnumReversed<T>.Create(Self); END; This is the code I used for testing: ... Var t:tListReversed<Integer>; i:integer; begin t:=tListReversed<Integer>.Create; t.Add(1); t.Add(2); t.Add(3); For i in T do memo1.lines.add(inttostr(i)) t.free; end; The weird thing is, the code runs correctly if I make the following change.... And I have literally no idea why that is the case! As far as I can see, the base class tEnumerable<T> already has a method GetEnumerator which should call my overridden virtual Method DoGetEnumerator. What am I missing here ??? tListReversed<T> = CLASS(tlist<T>) PROTECTED FUNCTION DoGetEnumerator: tEnumerator<T>; OVERRIDE; PUBLIC FUNCTION GetEnumerator: TEnumerator<T>; END; ... function tListReversed<T>.GetEnumerator: TEnumerator<T>; begin result:=DoGetEnumerator; end;
  6. I want to recursively walk the properties of MyVar: TMyOuterType - but the Items list may be empty. How can I walk the base element type of Items, i.e. TMyType - when I have no instance data? type TMyType = class public property One: string; property Two: string; end; TMyType2 = class(TMyType) public property Two: string; end; TMyType3 = class(TMyType2) public property Three: string; end; TMyTypeArray = TArray<TMyType>; // i.e. polymorphic TMyOuterType = class public property Items: TMyTypeArray; end; var MyVar: TMyOuterType;