使用Model View Presenter（MVP）验证UI控件

Question

I have been using winforms for many years. Normally I write a form and that form, in the code behind does everything (validates user input, communicates with the database…). Recently a friend introduced me to MVP and I have been trying to learn to use it. The problem I am having is replicated some of the stuff I used to be able to do with the form. For example, in the past if I had a textbox and the user entered something invalid in the textbox, I could turn that textbox red, set focus on the textbox and alert the user that they entered something invalid in that testbox. With my validation now being done in the presenter or model layer, I can Messagebox the user that something is not valid but how can I setfocus to a control or change a controls color?

Answer 1

Your presenter holds a reference to the view anyway, so you can just manipulate the widgets (text boxes etc.) directly from the presenter. Or, possibly better, have a method in the view like nameIsInvalid() , where you write your desired behaviour (changing color, setting focus). This method is called when the presenter notices that the input validation has failed.

The validation itself should be done in the model, since that is view-independent.

As always, you don't need to be super dogmatic about that. If it makes sense to have some simple validation associated directly with the widget, then leave it there. But a final validation of the whole form should be handled as I've described above.