表单的动态ChoiceField

创建并初始化动态ChoiceFiled的方法：

class ViewListForm(forms.Form):
    UIViewId = forms.ChoiceField()
    def __init__(self,UIViewList,*args, **kwargs):
        super(ViewListForm, self).__init__(*args, **kwargs)
        self.fields['UIViewId'] = forms.ChoiceField(choices=[(UIView["Id"], UIView["Name"]) for UIView in UIViewList])