string Delphi：调用名称存储在字符串中的函数
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Delphi: Call a function whose name is stored in a string
提问by Woutb21
Is it possible to call a function whose name is stored in a string in Delphi?
是否可以在 Delphi 中调用名称存储在字符串中的函数？
回答by himself
Please give more details on what are you trying to achieve.
请详细说明您要实现的目标。
As far as I know:
据我所知：
- It is not possible to call a random function like that.
- For class and object functions (MyObject.Function) this can be done with RTTI, but it's a lot of work.
- If you just need to call one particular type of functions (say, function(integer, integer): string), it's a lot easier.
- 不可能像那样调用随机函数。
- 对于类和对象函数 (MyObject.Function)，这可以通过 RTTI 来完成，但需要做很多工作。
- 如果您只需要调用一种特定类型的函数（例如 function(integer, integer): string），那就容易多了。
For the last one, declare a function type, then get a function pointer and cast it like this:
对于最后一个，声明一个函数类型，然后获取一个函数指针并像这样转换它：
type
TMyFuncType = function(a: integer; b: integer): string of object;
TMyClass = class
published
function Func1(a: integer; b: integer): string;
function Func2(a: integer; b: integer): string;
function Func3(a: integer; b: integer): string;
public
function Call(MethodName: string; a, b: integer): string;
end;
function TMyClass.Call(MethodName: string; a, b: integer): string;
var m: TMethod;
begin
m.Code := Self.MethodAddress(MethodName); //find method code
m.Data := pointer(Self); //store pointer to object instance
Result := TMyFuncType(m)(a, b);
end;
{...}
//use it like this
var MyClass: TMyClass;
begin
MyClass := TMyClass.Create;
MyClass.Call('Func1', 3, 5);
MyClass.Call('Func2', 6, 4);
MyClass.Destroy;
end.
回答by Mohammed Nasman
You didn't specify your Delphi version, However if you have Delphi 2010(+) you can do it using the enhanced RTTI, I'm not expert on them, but I tried this sample for you:
你没有指定你的 Delphi 版本，但是如果你有 Delphi 2010(+) 你可以使用增强的 RTTI 来做，我不是他们的专家，但我为你尝试了这个示例：
TProcClass = class
public
procedure SayHi;
function GetSum(X,Y:Integer): Integer;
end;
uses
Rtti;
{ TProcClass }
procedure TProcClass.SayHi;
begin
ShowMessage('Hi');
end;
function TProcClass.GetSum(X, Y: Integer): Integer;
begin
ShowMessage(IntToStr(X + Y));
end;
procedure ExecMethod(MethodName:string; const Args: array of TValue);
var
R : TRttiContext;
T : TRttiType;
M : TRttiMethod;
begin
T := R.GetType(TProcClass);
for M in t.GetMethods do
if (m.Parent = t) and (m.Name = MethodName)then
M.Invoke(TProcClass.Create,Args)
end;
procedure TForm1.FormCreate(Sender: TObject);
begin
ExecMethod('SayHi',[]);
ExecMethod('GetSum',[10,20]);
end;
The good things, if you have procedure or function with parameters it will work without more work.
好东西，如果你有带参数的过程或函数，它会在没有更多工作的情况下工作。
回答by Kenneth Cochran
I'm surprised no one has suggested a dispatch table. This is exactly what it's for.
我很惊讶没有人建议使用调度表。这正是它的用途。
program RPS;
uses
SysUtils,
Generics.Collections;
type
TDispatchTable = class(TDictionary<string, TProc>);
procedure Rock;
begin
end;
procedure Paper;
begin
end;
procedure Scissors;
begin
end;
var
DispatchTable: TDispatchTable;
begin
DispatchTable := TDispatchTable.Create;
try
DispatchTable.Add('Rock', Rock);
DispatchTable.Add('Paper', Paper);
DispatchTable.Add('Scissors', Scissors);
DispatchTable['Rock'].Invoke; // or DispatchTable['Rock']();
finally
DispatchTable.Free;
end;
end.
The implementation I wrote uses generics so it would only work with Delphi 2009+. For older versions it would probably be easiest to implement using TStringList and the command pattern
我编写的实现使用泛型，因此它只能与 Delphi 2009+ 一起使用。对于旧版本，使用 TStringList 和命令模式可能最容易实现
回答by Henri Gourvest
With Delphi 2010 you can uses JSON and SuperObject to invoke method with parametters.
使用 Delphi 2010，您可以使用 JSON 和 SuperObject 来调用带参数的方法。
http://code.google.com/p/superobject/source/browse/#svn/trunk
http://code.google.com/p/superobject/source/browse/#svn/trunk
If you need, there is also an xml parser to transform xml to json.
如果需要，还有一个 xml 解析器可以将 xml 转换为 json。
TForm1 = class(TForm)
Button1: TButton;
procedure Button1Click(Sender: TObject);
private
{ Private declarations }
public
{ Public declarations }
procedure TestMethod(const value: string);
end;
var
Form1: TForm1;
implementation
uses superobject;
{$R *.dfm}
procedure TForm1.Button1Click(Sender: TObject);
begin
SOInvoke(Self, 'TestMethod', SO('{value: "hello"}'));
end;
procedure TForm1.TestMethod(const value: string);
begin
Caption := value;
end;
回答by AlexV
If you are asking if there is something like the JavaScript eval()is possible in Delphi, no this is not (easily) achievable since Delphi compiles to native code.
如果您问eval()Delphi 中是否可以使用 JavaScript 之类的东西，不，这不是（很容易）实现的，因为 Delphi 编译为本机代码。
If you need only to support some strings you can always do many ifor a case... Something like:
如果你只需要支持一些字符串，你总是可以做很多if或case......类似的事情：
if myString = 'myFunction' then
myFunction();
回答by Rob McDonell
Put each function in an Action. Then you can find the Action by name and Execute it
将每个函数放在一个 Action 中。然后你可以按名称找到Action并执行它
function ExecuteActionByName(const S: String);
var
I: Integer;
begin
for I := 0 to MainForm.ComponentCount-1 do
if (MainForm.Components[I] is TAction)
and SameText(TAction(MainForm.Components[I]).Name,S) then
begin
TAction(MainForm.Components[I]).Execute;
Break;
end;
end;
回答by TheDude
OK, I'm verylate to the party, but you can definitely call routines by name with this code (There are some limitations thought)
OK，我非常迟到了，但你绝对可以调用名称程序使用此代码（有一些限制以为）
type
TExec = procedure of Object;
// rest of section...
procedure TMainForm.ExecuteMethod(MethodName : String);
var
Exec : TExec;
Routine : TMethod;
begin
Routine.Data := Pointer(Form1);
Routine.Code := Form1.MethodAddress(MethodName);
if Not Assigned(Routine.Code) then
Exit;
Exec := TExec(Routine);
Exec;
end;
Just in case someone needs this for Delphi 7 / 2010
以防万一有人需要这个用于 Delphi 7 / 2010
回答by Larry Lustig
You can do something like this by crafting one or more classes with published properties that use functions to implement their read and write functionality. The properties can then be discovered using RTTI reflection and referenced, causing the underlying functions to get called.
您可以通过制作一个或多个具有已发布属性的类来执行类似的操作，这些属性使用函数来实现其读写功能。然后可以使用 RTTI 反射发现并引用这些属性，从而调用底层函数。
Alternatively, you can store function pointers in a table, or even the Object property of TStringList and effectively index them by string name.
或者，您可以将函数指针存储在表中，甚至是 TStringList 的 Object 属性中，并按字符串名称有效地索引它们。
Straight calling of a function by name is not possible in Delphi.
在 Delphi 中无法直接按名称调用函数。
回答by Daniel
The following simple solution using exportsand GetProcAddressalso works for old Delphi versions:
以下使用导出和GetProcAddress 的简单解决方案也适用于旧的 Delphi 版本：
type
TMyProc = procedure(const value: Integer);
procedure Test(const value: Integer);
exports Test;
implementation
procedure Test(const value: string);
begin
ShowMessage('It works! ' + value);
end;
procedure TForm1.Button1Click(Sender: TObject);
var
p: TMyProc;
begin
p := GetProcAddress(HInstance, 'Test');
if Assigned(p) then P('Yes');
end;
回答by MrClarc
function ExecuteMethod(AClass : TClass; AMethodName : String; const AArgs: Array of TValue) : TValue;
var
RttiContext : TRttiContext;
RttiMethod : TRttiMethod;
RttiType : TRttiType;
RttiObject : TObject;
begin
RttiObject := AClass.Create;
try
RttiContext := TRttiContext.Create;
RttiType := RttiContext.GetType(AClass);
RttiMethod := RttiType.GetMethod(AMethodName);
Result := RttiMethod.Invoke(RttiObject,AArgs);
finally
RttiObject.Free;
end;
end;
