How can I verify text of text input

Question

Hey everyone I want to verify a text input and it doesn't work. I don't know why. Here is the code, btw I tried EVERYTHING and it doesn't work so don't talk about self.root.ids.id.text, IT JUST DOESN'T WORK. :

class ReviewinApp(MDApp):
    def build(self):
        dialog = None
        self.title = "ReviewinApp"
        global sm 
        sm = ScreenManager()
        sm.add_widget(Builder.load_file("splash.kv"))
        sm.add_widget(Builder.load_file("accueil.kv"))
        sm.add_widget(Builder.load_file('conditions.kv'))
        sm.add_widget(Builder.load_file("register.kv"))
        sm.add_widget(Builder.load_file("faq.kv"))
        sm.add_widget(Builder.load_file("login.kv"))
        sm.add_widget(Builder.load_file("User2.kv"))
        sm.add_widget(Builder.load_file("rules.kv"))
        sm.add_widget(Builder.load_file("commentinput.kv"))
        sm.add_widget(Builder.load_file("UserInfo.kv"))
        return sm
    def check_text(self):
        if self.ids.full_name.text == 'g':
            print("g")
        else:
            return False

MDScreen:
    name:"register"
    MDFloatLayout:
        md_bg_color: 41/255, 34/255, 34/255, 1
        MDTextFieldRound:
            id:full_name
            text: ""
            hint_text: "Full Name"
            size_hint_x:  None
            size_hint_y: 0.08
            width: 247
            font_size: 18
            pos_hint: {'center_x':0.5, 'center_y':0.7}

       MDFillRoundFlatButton:
            text: "Finish !"
            font_size: "20sp"
            font_name: "OpenSans"
            pos_hint: {'center_x':0.5, 'center_y':0.1}
            halign: 'center'
            theme_text_color:'Custom'
            text_color: 255/255, 255/255, 255/255, 1
            size_hint: (0.58, 0.06)
            md_bg_color: 62/255, 216/255, 133/255, 1
            background_normal:''
            on_press: app.check_text()

Answer 1

I don't get that error, but I do get an error.

If you access an id that is defined in a kv file, you must access it through the ids of the object that is the root object that contains that id. In this case, the full_name id is defined in the kv that you posted. The root that contains the id is the MDScreen, so you must access it through the ids of that MDScreen:

def check_text(self):
    if self.root.current_screen.ids.full_name.text == 'g':
        print("g")
    else:
        return False