import maya.cmds as mc

class SimpleUI(object):
    def __init__(self, *args):
        self.wg={}
        self.wg['win'] = 'MySimpleWindow'
        self.wg['dock'] = 'MySimpleDock'
        
        if mc.dockControl(self.wg['dock'], exists=True):
            mc.deleteUI(self.wg['dock'])
        # window
        mc.window(self.wg['win'])
        # layout
        mc.rowColumnLayout(nc=1)
        """ controls """
        mc.button(l='textField_button', 
                  c=self.com_button_command)
        # this works
        self.wg['textField'] = mc.textField()
        mc.button(l='textFieldGrp_button',
                  c=self.com_grp_button_command)
        # this does not work
        self.wg['textFieldGrp'] = mc.textFieldGrp()
        mc.dockControl(self.wg['dock'],
                       area='left',
                       content=self.wg['win'])

    def com_button_command(self, *args):
        # this works
        mc.textField(self.wg['textField'], e=True, tx='blabla')
        
    def com_grp_button_command(self, *args):
        # this does not work
        mc.textFieldGrp(self.wg['textFieldGrp'], e=True, tx='blabla')
        
SimpleUI()


"""Error Code"""
# // Error: RuntimeError: file <maya console> line 36: 
#    Object 'MySimpleWindow|rowColumnLayout10|textFieldGrp26' not found. //