Brtdku

I have created a website using flask and Jinja template. I have created a login and signup form. In the header of my homepage, there is signup and login. After logging in I wanna replace login/signup with logout. If there is any solution to it tell me. It will be very helpful. Thanks in advance. The codes are given below.

index.html

<nav class="navbar navbar-inverse navbar-fixed-top" style="background-color: 



    white; border-bottom: #dddddd solid 1px;border-top: none;border-left: none;border-right: none;">

        <div class="container-fluid">

          <div class="navbar-header">

            <button type="button" class="navbar-toggle" data-toggle="collapse" data-target="#myNavbar">

              <span class="icon-bar"></span>

              <span class="icon-bar"></span>

              <span class="icon-bar"></span> 

            </button>

            <a class="navbar-brand" href="#" style="padding: 10px 20px;margin: 20px 0;">WebSiteName</a>

          </div>

          <div class="collapse navbar-collapse" id="myNavbar">

            <!--ul class="nav navbar-nav">

              <li class="active"><a href="#">Home</a></li>

              <li><a href="#"></a></li>

              <li><a href="#">Page 2</a></li> 

              <li><a href="#">Page 3</a></li> 

            </ul-->

            <ul class="nav navbar-nav navbar-right ul1">

              <li class="li1"><a id="a1" style="color: red;" href="{{ url_for('index') }}">Home</a></li>

          <li class="li1"><a id="a1" href="{{ url_for('.index', _anchor='about') }}">About Product</a></li>

          <li class="li1"><a id="a1" href="{{ url_for('.index', _anchor='foot') }}">Contact Us</a></li>

          {% if is_authenticated == 'true' %}

          <li class="li1"><a id="a1" href="{{ url_for('logout') }}">Logout</a></li>

          {% else %}

          <li class="li1"><a id="a1" href="{{ url_for('signup') }}">Signup</a></li>

          <li class="li1"><a id="a1" href="{{ url_for('login') }}">Login</a></li>

          {% endif %}

              <!--li><a href="#"><span class="glyphicon glyphicon-user"></span> Sign Up</a></li>

              <li><a href="#"><span class="glyphicon glyphicon-log-in"></span> Login</a></li-->

            </ul>

          </div>

        </div>

      </nav>

app.py

from flask import Flask, render_template, redirect, url_for, flash

from flask_bootstrap import Bootstrap

from flask_wtf import FlaskForm 

from wtforms import StringField, PasswordField, BooleanField

from wtforms.validators import InputRequired, Email, Length

from flask_sqlalchemy  import SQLAlchemy

from werkzeug.security import generate_password_hash, check_password_hash

from flask_login import LoginManager, UserMixin, login_user, login_required, logout_user, current_user



app = Flask(__name__)

app.config['SECRET_KEY'] = 'Thisissupposedtobesecret!'

app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite:///database.db'

Bootstrap(app)

db = SQLAlchemy(app)

login_manager = LoginManager()

login_manager.init_app(app)

login_manager.login_view = 'login'



class User(UserMixin, db.Model):

    id = db.Column(db.Integer, primary_key=True)

    username = db.Column(db.String(15), unique=True)

    email = db.Column(db.String(50), unique=True)

    password = db.Column(db.String(80))



    def is_authenticated(self):

        """Return True if the user is authenticated."""

        return self.authenticated



@login_manager.user_loader

def load_user(user_id):

    return User.query.get(int(user_id))



class LoginForm(FlaskForm):

    username = StringField('Username', validators=[InputRequired(), Length(min=4, max=15)])

    password = PasswordField('Password', validators=[InputRequired(), Length(min=8, max=80)])

    remember = BooleanField('Remember me')



class RegisterForm(FlaskForm):

    email = StringField('Email', validators=[InputRequired(), Email(message='Invalid email'), Length(max=50)])

    username = StringField('Username', validators=[InputRequired(), Length(min=4, max=15)])

    password = PasswordField('Password', validators=[InputRequired(), Length(min=8, max=80)])



@app.route('/')

def index():

    return render_template('index.html')



@app.route('/login', methods=['GET', 'POST'])

def login():

    form = LoginForm()



    if form.validate_on_submit():

        user = User.query.filter_by(username=form.username.data).first()

        if user:

            if check_password_hash(user.password, form.password.data):

                login_user(user, remember=form.remember.data)

                return redirect(url_for('dashboard'))



        return '<h1>Invalid username or password</h1>'

        #return '<h1>' + form.username.data + ' ' + form.password.data + '</h1>'



    return render_template('login.html', form=form)



@app.route('/signup', methods=['GET', 'POST'])

def signup():

    form = RegisterForm()



    if form.validate_on_submit():

        hashed_password = generate_password_hash(form.password.data, method='sha256')

        new_user = User(username=form.username.data, email=form.email.data, password=hashed_password)

        db.session.add(new_user)

        db.session.commit()

        flash('User successfully registered')

        return redirect(url_for('login'))

        #return '<h1>' + form.username.data + ' ' + form.email.data + ' ' + form.password.data + '</h1>'





    return render_template('signup.html', form=form)



@app.route('/dashboard')

@login_required

def dashboard():

    return render_template('dashboard.html', name=current_user.username)



@app.route('/logout')

@login_required

def logout():

    logout_user()

    return redirect(url_for('index'))



if __name__ == '__main__':

    app.run(debug=True)

Set a session variable when login is successful and check in the template if that has been set. When logging out you could set it to False.

This is not an exact match for your code but just samples which you can apply with modification.

app.py

from flask import Flask, request, render_template, session

.....

@app.route('/login', methods=['POST', 'GET'])

def login():

    error = None

    if request.method == 'POST':

        if valid_login(request.form['username'],request.form['password']):

            session['logged_in'] = True

            return render_template('index.html')

        else:

            error = 'Invalid username or password'

    return render_template('login.html', error=error)



@app.route("/logout")

def logout():

    session['logged_in'] = False

    return render_template('login.html') 

......

In your template.

......    

{% if session['logged_in'] %}   

<!-- Logged in -->

{% else %}

<!-- Not Logged in -->

{% endif %}

........

Just use the built-in current_user from flask-login in your template like this:

{% if current_user.is_authenticated %}

-- place logout button here --

{% else %}

-- place login button here --

{% endif %}