Jump to content

Search the Community

Showing results for tags 'generics'.

More search options

  • Search By Tags

    Type tags separated by commas.
  • Search By Author

Content Type


  • Delphi Questions and Answers
    • Algorithms, Data Structures and Class Design
    • VCL
    • FMX
    • RTL and Delphi Object Pascal
    • Databases
    • Network, Cloud and Web
    • Windows API
    • Cross-platform
    • Delphi IDE and APIs
    • General Help
  • Delphi General Discussions
    • Embarcadero Lounge
    • Tips / Blogs / Tutorials / Videos
    • Delphi Third-Party
    • Job Opportunities / Coder for Hire
    • I made this
  • Software Development
    • Project Planning and -Management
    • Software Testing and Quality Assurance
  • Community
    • Community Management

Find results in...

Find results that contain...

Date Created

  • Start


Last Updated

  • Start


Filter by number of...


  • Start




Found 3 results

  1. 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?
  2. 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;
  3. 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;