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Flask framework - Message flash

2022-07-25 10:53:00 【White chocolate Lin】

Catalog

In the last article, we learned Flask frame ——flask-caching cache , Let's study this article Flask frame ——flash The news flashed .

good web The application needs to provide feedback to users , for example ： When the user enters information and clicks submit , The web page will prompt whether the submission is successful or the submitted information is incorrect .

Flask The framework provides a simple way of feedback through the flash system . Its basic working principle is ： Record a message at the end of the current request , Provide to the current request or the next request . for example ： The user is in A Jump to B page , stay B The page shows A Page error messages . At this time, the error message can be passed to B page .

Use message flash

Flask The framework provides flash() Method to realize message flash , In the view function, use flash() Method to pass the message to the next request , This request is usually a template .

flash() The syntax structure of the method is ：

flash(message,category)

among ：

message： Mandatory , Data and information ;
category： Optional , Flash type .

Be careful ： When using message flash , Need configuration SECRET_KEY Value , The value can be any character .

The sample code is as follows :

from flask import Flask, render_template, request, flash

app = Flask(__name__)
app.config['SECRET_KEY']='sfasf'    # To configure SECRET_KEY, The value is any character 

@app.route('/',methods=['GET','POST'])
def flash_message():
    if request.method=='POST':
        username=request.form.get('username')   # Get submitted username value 
        if username=='admin':     # Verify that it is admin
            flash(' Verify success ')     # Use flash Method to pass information 
            return render_template('index.html') # Use render_template() Method render template index.html
        else:
            flash(' Validation failed ')     # Use flash Method to pass information 
            return render_template('index.html') # Use render_template() Method render template index.html
    return render_template('login.html')  # Use render_template() Method render template login.html

if __name__ == '__main__':
    app.run()

Here we simply pass on the information by obtaining the information filled in by the user to judge whether it is correct , stay login.html The template code is ：

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<form action="{
   { url_for('flash_message') }}" method="post">
    <p><input type="text" name="username" placeholder=" enter one user name "></p>
    <p><input type="submit" value=" Submit "></p>
</form>
</body>
</html>

Create a form Form and bind the flash_message(), Create text boxes and buttons to complete a simple submission page .

stay index.html In the template , Use get_flashed_messages() Method to get the message , The code is as follows ：

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title> home page </title>
</head>
<body>
{% with messages=get_flashed_messages() %}  {#  Use get_flashed_messages() Method get message #}
    {% if messages %}      
        {% for message in messages %}
            {
   { message }}
        {% endfor %}
    {% endif %}
{% endwith %}
</body>
</html>

Be careful ： Use get_flashed_messages() The message obtained by the method is saved in tuples , So you can go through for Loop to get .

Start our flask Program , visit http://127.0.0.1:5000/, As shown in the figure below ：

Flask14--- perform flask flash

When we type in admin And click Submit , Will jump to the web , This page displays ： Verify success ;

When we enter other characters, click Submit , Will jump to the web , This page displays ： Validation failed .

Message flash classification

Use flash() When the method is used , We can pass on category Parameters , Its value can be error( error )、info( Information )、warning( Warning ), The sample code is as follows ：

from flask import Flask, render_template, request, flash

app = Flask(__name__)
app.config['SECRET_KEY']='sfasf'    # To configure SECRET_KEY, The value is any character 

@app.route('/',methods=['GET','POST'])
def flash_message():
    if request.method=='POST':
        username=request.form.get('username')   # Get submitted username value 
        if username=='admin':     # Verify that it is admin
            flash(' Verify success ','info')    # Use flash Method to pass information , The flash type is ：info
            return render_template('index.html') # Use render_template() Method render template index.html
        else:
            flash(' Validation failed ','error')    # Use flash Method to pass information , The flash type is ：error
            return render_template('index.html') # Use render_template() Method render template index.html
    return render_template('login.html')  # Use render_template() Method render template login.html

if __name__ == '__main__':
    app.run()

stay index.html In the template , In the use of get_flashed_messages() when , Delivery required with_categories Parameters , Its value is true, Indicates the receiving flash type , The code is as follows ：

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title> home page </title>
</head>
<body>
{% with messages=get_flashed_messages(with_categories=true) %}  {# Use get_flashed_messages() Method #}
    {% if messages %}
        <ul>
            {% for category , message in messages %}
                <li class="{
   { category }}">{
   { message }}</li>
            {% endfor %}
        </ul>
    {% endif %}
{% endwith %}
</body>
</html>

Filter flash messages

When we set multiple flashes in the view function , At this time, we can use in the template file get_flashed_messages() Method passing category_filter Parameters to select the flash message we need to display , For example, in the view function above flash(' Verify success ','info') Add the following... Under the code flash() Flash code ：

from flask import Flask, render_template, request, flash

app = Flask(__name__)
app.config['SECRET_KEY']='sfasf'    # To configure SECRET_KEY, The value is any character 

@app.route('/',methods=['GET','POST'])
def flash_message():
    if request.method=='POST':
        username=request.form.get('username')   # Get submitted username value 
        if username=='admin':     # Verify that it is admin
            flash(' Verify success ','info')    # Use flash Method to pass information , The flash type is ：info
            flash(' Please don't believe any advertisements ','warning')   # Use flash Method to pass information , The flash type is ：warning
            return render_template('index.html') # Use render_template() Method render template index.html
        else:
            flash(' Validation failed ','error')    # Use flash Method to pass information , The flash type is ：error
            return render_template('index.html') # Use render_template() Method render template index.html
    return render_template('login.html')  # Use render_template() Method render template login.html

if __name__ == '__main__':
    app.run()

stay index.html In the template file , The code is as follows ：

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title> home page </title>
</head>
<body>
{% with messages=get_flashed_messages(category_filter=['warning']) %} {# Use get_flashed_messages() Method #}
    {% if messages %}
        {% for  message in messages %}
            {
   { message }}
        {% endfor %}
    {% endif %}
{% endwith %}
</body>
</html>

Here we filter and select warning Flash type of type , start-up flask Program , visit http://127.0.0.1:5000/,

When we type in admin And click Submit , Will jump to the web , This page displays ： Please don't believe any advertisements ;

Be careful ： Information cannot be compared with Cookie Big , Otherwise, it will cause flash silence failure .

Okay ,Flask frame —— That's all for the flash message , Thank you for watching. , Let's continue our study in the next article Flask frame ——Flask-WTF Forms ： data validation 、CSRF Protect .

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