登录之后更新导航

1、用上下文处理器app_context_processor定义函数

获取session中保存的值

返回字典

2、在父模板中更新导航，插入登录状态判断代码。、

注意用{% ... %}表示指令。

{{ }}表示变量

3、完成注销功能。

清除session

跳转

@app.context_processor
def mycontext():
    usern=session.get('user')
    if usern:
        return{'username':usern}
    else:
        return{}

 <p>{{ username }}一三</p>

{% if username %}
                <a href="#">
                <button type="button" class="btn btn-default"><span class="glyphicon glyphicon-log-in"></span>{{ username }}
                </button>
                </a>
                <a href="{{ url_for('logout') }}">
                    <button type="button" class="btn btn-default"><span class="glyphicon glyphicon-user"></span> 注销                   </button>
                </a>
                {% else %}
                <a href="{{ url_for('login') }}">
                    <button type="button" class="btn btn-default"><span class="glyphicon glyphicon-log-in"></span>登录
                    </button>
                </a>
                <a href="{{ url_for('regist') }}">
                    <button type="button" class="btn btn-default"><span class="glyphicon glyphicon-user"></span> 注册
                    </button>
                </a>
                {%  endif %}<a href="#">
                <button type="button" class="btn btn-default"><span class="glyphicon glyphicon-log-in"></span>{{ username }}
                </button>
                </a>
                <a href="{{ url_for('logout') }}">
                    <button type="button" class="btn btn-default"><span class="glyphicon glyphicon-user"></span> 注销                   </button>
                </a>
                {% else %}
                <a href="{{ url_for('login') }}">
                    <button type="button" class="btn btn-default"><span class="glyphicon glyphicon-log-in"></span>登录
                    </button>
                </a>
                <a href="{{ url_for('regist') }}">
                    <button type="button" class="btn btn-default"><span class="glyphicon glyphicon-user"></span> 注册
                    </button>
                </a>
                {%  endif %}

@app.route('/logout')
def logout():
    session.clear()
    return redirect(url_for('base'))