Question

如何使用最终RTTI在运行时创建可视组件作为表单的子项？我得到的只是一个TValue实例......

 t := (ctx.FindType(Edit1.Text) as TRttiInstanceType);
 inst:= t.GetMethod('Create').Invoke(t.MetaclassType,[Form1]);

谢谢！

Answer 1

使用TRttiMethod.Invoke()的纯粹RTTI方法看起来像这样：

var
  ctx: TRttiContext;
  t: TRttiInstanceType;
  m: TRttiMethod;
  params: TArray<TRttiParameter>;
  v: TValue;
  inst: TControl;
begin
  t := ctx.FindType(Edit1.Text) as TRttiInstanceType;
  if t = nil then Exit;
  if not t.MetaclassType.InheritsFrom(TControl) then Exit;
  for m in t.GetMethods('Create') do
  begin
    if not m.IsConstructor then Continue;
    params := m.GetParameters;
    if Length(params) <> 1 then Continue;
    if params[0].ParamType.Handle <> TypeInfo(TComponent) then Continue;
    v := m.Invoke(t.MetaclassType, [TComponent(Form1)]);
    inst := v.AsType<TControl>();
    // or: inst := TControl(v.AsObject);
    Break;
  end;
  inst.Parent := ...;
  ...
end;

不使用TRttiMethod.Invoke()的更简单方法如下所示：

type
  // TControlClass is defined in VCL, but not in FMX
  TControlClass = class of TControl;

var
  ctx: TRttiContext;
  t: TRttiInstanceType;
  inst: TControl;
begin
  t := ctx.FindType(Edit1.Text) as TRttiInstanceType;
  if t = nil then Exit;
  if not t.MetaclassType.InheritsFrom(TControl) then Exit;
  inst := TControlClass(t.MetaclassType).Create(Form4);
  inst.Parent := ...;
  //...
end;

从字符串运行时创建Delphi Firemonkey组件

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