消息闪现

#消息闪现
@book_bp.route("/book", methods=["GET", "POST"])
def handle_book():
    if request.method == "POST":
        title = request.form.get("title")
        if title:
            books.append(title)
            flash("Add book succussfully.")
            return redirect(url_for("book.handle_book"))
        else:
            flash("Add failed", "error")
    return render_template("book.html", books=books)

#jinja模版中使用
    {% for message in get_flashed_messages()%}
        {{ message }}
    {% endfor %}

    {% with error_message = get_flashed_messages(category_filter=["error"]) %}
        {% for error in error_message %}
            {{ error }}
        {% endfor %}
    {% endwith %}