3

我想知道是否有解决此问题的基本方法。还对 Pascal 的特定解决方案特别感兴趣。

假设我们有一个带有 2 个输入的表单：“InputVARIABLE”和“InputVALUE”。

在 InputVARIABLE 区域中，用户键入他想要更改的变量的名称。在 InputVALUE 区域中，用户键入该变量的值。

因此，对于输入文本“颜色”和“蓝色”：如何在不使用 IF 语句的情况下更改变量 VAR_color，例如：

If InputVARIABLE.Text = 'color' Then VAR_color := InputVALUE.Text;

是否有一些功能，例如：

ChangeVariable(InputVARIABLE.Text, InputValue.Text)

希望你能帮忙！

4

2 回答 2

8

如果您不需要更改在 delphi 中预定义的实际变量，您实际上可以做其他事情。

您真正想要的只是保存键值对。

这在其他语言中称为关联数组/字典/键值对

所以你可以说

Arr['color'] := 'red';

或者说

Arr[edit1.Text] := edit2.Text;

然后反过来

Caption := Arr['color'];

将标题设置为“红色”或edit2.text中的任何内容，您可以添加任意数量的内容。

如果你有旧版本的 Delphi，你可以对 Tlist 类做同样的事情，只是不要嵌套。

arr:= TStringList.Create;
arr.Add('color=red');
s := arr.Values['color'];
arr.free;

我也需要嵌套，所以我使用 delphi XE3 中的字典创建了一个关联数组类，将来也可能对你有更多帮助。

unit assoc;

interface

uses System.Generics.Collections, System.SysUtils;

type TAssoc = class
  private
    fVal: Variant;
    fStrict: Boolean;
    fDict: TDictionary<Variant,TAssoc>;
    function GetItem(Index: Variant): TAssoc;
    procedure SetVal(v: Variant);
    function GetVal:Variant;
  public
    /// <summary>
    ///   Returns the TAssocnode by default allowing you to chain Nodes 
    /// </summary>
    /// <param name="Index">
    ///   Search index, can be any primitive type.
    /// </param>
    property Items[Index: Variant]: TAssoc read GetItem; default;

    /// <summary>
    ///   Use this to read and write a node value.
    /// </summary>
    /// <value>
    ///   can be almost everything Try not to use objects in here.
    /// </value>
    property Val:Variant read GetVal write SetVal;

    /// <summary>
    ///   Gives you a direct link to the tdictionary object alowing you to
    ///   itterate
    /// </summary>
    property All:TDictionary<Variant,TAssoc> read fDict;
    /// <summary>
    ///   <para>
    ///     Usefull for creating keys in strict mode
    ///   </para>
    ///   <para>
    ///     Array.add('key');<br />Array['key'].Val = 1;
    ///   </para>
    ///   <para>
    ///     Wich would throw an error in strict mode as 'key' is not defined
    ///     <br />In non strict mode it will just be created for you
    ///   </para>
    /// </summary>
    function Add(Index: Variant):TAssoc; overload;
    /// <summary>
    ///   <para>
    ///     Usefull for creating keys in strict mode and setting its value at the same time
    ///   </para>
    ///   <para>
    ///     Array.add('key',1);<br />Array['key'].Val = 1;
    ///   </para>
    ///   <para>
    ///     Wich would throw an error in strict mode as 'key' is not defined
    ///     <br />In non strict mode it will just be created for you
    ///   </para>
    /// </summary>
    function Add(Index: Variant; Value: Variant):TAssoc; overload;

    /// <summary>
    ///   Strictmode will raise an exception when you try to:<br />- set a nod
    ///   that was already set instead of overwriting it.<br />- read a node
    ///   that was nto set
    /// </summary>
    /// <param name="strictRules">
    ///   Strictmode on of off
    /// </param>
    constructor Create(strictRules:Boolean);
    destructor Free;

    /// <summary>
    ///   Clears all underlying nodes
    /// </summary>
    procedure Clear;
end;

type TAssocEnum = TPair<Variant, TAssoc>;

implementation

{ TAssoc }

function TAssoc.Add(Index: Variant): TAssoc;
begin
  Result := nil;
  if(fDict<>nil) then begin // see if dict is or can be made
    if(fDict.ContainsKey(Index)) then begin // see if the key is in there
      if(fStrict = true) then begin // duplicate keys not strict
        raise Exception.Create('Dictionary is in strict mode, the key "'+Index+'" was already set.');
      end;
    end else begin // dict made, just not the key
      Result := TAssoc.Create(fStrict);
      fDict.Add(Index,Result);
    end;
  end else begin // dict not found
    begin // make dict and key
      fDict := TDictionary<Variant,TAssoc>.Create(1);
      Result := TAssoc.Create(fStrict);
      fDict.Add(Index,Result);
    end;
  end;
end;

function TAssoc.Add(Index, Value: Variant): TAssoc;
begin
  Result := Add(Index);
  Result.Val := Value;
end;

procedure TAssoc.Clear;
var
  Enum: TPair<Variant, TAssoc>;
begin
  if(fDict<>nil) then begin
    for Enum in fDict do begin
      Enum.Value.Free;
    end;
  end;
  fDict.Clear;
end;

constructor TAssoc.Create(strictRules:Boolean);
begin
  fStrict := strictRules;
  fDict := nil;
  TVarData(fVal).VType := varEmpty;
end;

destructor TAssoc.Free;
var
  Enum: TPair<Variant, TAssoc>;
begin
  if(fDict<>nil) then begin
    for Enum in fDict do begin
      Enum.Value.Free;
    end;
  end;
end;

function TAssoc.GetItem(Index: Variant): TAssoc;
var
  v: Variant;
begin
  Result := nil;
  if(fdict<>nil) then begin // see if dict is or can be made
    if(fDict.ContainsKey(Index)) then begin // see if the key is in there
      Result := fDict.Items[Index];
    end else begin // dict made, just not the key
      if (fStrict) then begin
        raise Exception.Create('Dictionary is in strict mode, the key "'+Index+'" was not set.');
      end else begin // if not set, create the index and make it into a assocnode
        Result := TAssoc.Create(fStrict);
        fDict.Add(Index,Result);
      end;
    end;
  end else begin // if the key is not in there see if strict or not
    if(fStrict) then begin // if strict then error index not set
      raise Exception.Create('Dictionary is in strict mode, the key "'+Index+'" was not set.');
    end else begin // if not set, create the index and make it into a assocnode
      fDict := TDictionary<Variant,TAssoc>.Create(1);
      Result := TAssoc.Create(fStrict);
      fDict.Add(Index,Result);
    end;
  end;
end;

function TAssoc.GetVal: Variant;
begin Result := fVal; end;

procedure TAssoc.SetVal(v: Variant);
begin fVal := v; end;

// todo:
// make a kickass helper class
// output xml/json
// walk through tree
// parentnode property?
// make a delphi7 version using stringlist? (not worth it)
// have fun

end.

简单用法

Arr := TAssoc.Create(False);
Arr['color'].Val := 'red';
Arr[edit1.text].Val := edit2.text;
Arr.Free;

高级用法

Arr := TAssoc.Create(False);
Arr['cuzz']['cdcollection'][1]['name'].Val := 'Mika Album'; // set cd
Arr['cuzz']['cdcollection'][2]['name'].Val := 1;            // set cd
Arr['cuzz']['cdcollection'][1]['name'].Val := 'Delphi 5';   // overwrite cd
Arr['cuzz']['cdcollection']['last']['name'].Val := 'Delphi xe3';   // overwrite cd
// list all cd's
for Enum in Arr['cuzz']['cdcollection'].All do begin
  Memo1.Lines.Append('Property "'+String(Enum.Key)+'" holds "'+String(Enum.Value['name'].Val));
end;
Arr.Free;

德尔福摇滚！享受。

于 2013-04-06T19:02:03.290 回答
2

通常，您不能在 Pascal 中使用它们在文本表示（字符串）中的名称来访问符号

Object Pascal/Delphi 对此有一些扩展，但它们主要用于特定目的（例如，允许框架在不知情的情况下流式传输数据），而对于普通代码则较少。

所以需要改变计划。通常你在一个变量名数组（如果是 Object Pascal 则为 tstringlist）中查找名称，如果找到有效匹配项，则使用索引将结果设置在数组中。

于 2013-04-06T12:20:19.763 回答