学习DELPHI最好的方法是看DELPHI的VCL原代码爱看他的机制本文就类TComponent的原代码来看他的机制. { TComponent } constructor TComponent.Create(AOwner: TComponent); begin FComponentStyle := [csInheritable]; if AOwner <> nil then AOwner.InsertComponent(Self); end;
procedure TComponent.InsertComponent(AComponent: TComponent); begin AComponent.ValidateContainer(Self); ValidateRename(AComponent, '''''''', AComponent.FName);//看是否有重名的对象如果有则发异常 Insert(AComponent);//在自己的子组件列表里加入AComponent的引用 AComponent.SetReference(True); if csDesigning in ComponentState then AComponent.SetDesigning(True); Notification(AComponent, opInsert);//给自己发一个通知消息 end;
procedure TComponent.ValidateRename(AComponent: TComponent; const CurName, NewName: string); begin if (AComponent <> nil) and not SameText(CurName, NewName) and (AComponent.Owner = Self) and (FindComponent(NewName) <> nil) then raise EComponentError.CreateResFmt(@SDuplicateName, [NewName]); if (csDesigning in ComponentState) and (Owner <> nil) then Owner.ValidateRename(AComponent, CurName, NewName);//递归调用查是否有重名的组件 end;
procedure TComponent.ValidateContainer(AComponent: TComponent); begin AComponent.ValidateInsert(Self); end;
procedure TComponent.ValidateInsert(AComponent: TComponent); begin end;
procedure TComponent.Insert(AComponent: TComponent);//我们可以看到他的子组件的引用是用TLIST来保存的 begin if FComponents = nil then FComponents := TList.Create; FComponents.Add(AComponent); AComponent.FOwner := Self;//给刚刚加上的主件赋上拥有者属性 end;
destructor TComponent.Destroy; file://可以看到每一个组件都维护一个FFREENOTIFILES的列表 begin Destroying; if FFreeNotifies <> nil then begin while Assigned(FFreeNotifies) and (FFreeNotifies.Count > 0) do TComponent(FFreeNotifies[FFreeNotifies.Count - 1]).Notification(Self, opRemove); FreeAndNil(FFreeNotifies);//如果自己析构的时候,对自己FFREENOTIFILES里面引用的对象调用Notification,把自己析构造的事件告诉他们 end; DestroyComponents; if FOwner <> nil then FOwner.RemoveComponent(Self); inherited Destroy; end;
procedure TComponent.FreeNotification(AComponent: TComponent);//通过这个过程可以证实FFREENOTIFILES是一个列表这个列表维护自己析构的时候给那些对象通知 begin if (Owner = nil) or (AComponent.Owner <> Owner) then begin // Never acquire a reference to a component that is being deleted. assert(not (csDestroying in (ComponentState + AComponent.ComponentState))); if not Assigned(FFreeNotifies) then FFreeNotifies := TList.Create; if FFreeNotifies.IndexOf(AComponent) < 0 then begin FFreeNotifies.Add(AComponent); AComponent.FreeNotification(Self); end; end; Include(FComponentState, csFreeNotification); end;
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