Goals:
- 學(xué)習(xí)使用WTForms.
- 學(xué)習(xí)使用Flask-WTF
- 學(xué)習(xí)使用如何寫Flask插件.
- 學(xué)習(xí)什么是CSRF(待完成).
- 學(xué)習(xí)flask中的redirect.
Part1 WTForms --- A Quick Start.
Let's begin from A mini example.
# flask_wtf_demo.py
from flask import Flask, render_template
from flask_wtf import Form
from wtforms import StringField, SubmitField
from wtforms.validators import DataRequired
app = Flask(__name__)
app.config['SECRET_KEY'] = "salt river"
class MyForm(Form):
name = StringField("what's your name", validators=[DataRequired()])
submit = SubmitField('Submit')
@app.route('/index', methods=('GET', 'POST'))
def submit():
name = None
form = MyForm()
if form.validate_on_submit():
name = form.name.data
form.name.data = ''
return render_template('index.html', form=form, name=name)
if __name__ == '__main__':
app.run(debug=True)
<!DOCTYPE html>
<html>
<head>
<title>Flask-WTF Demo</title>
</head>
<body>
<form method="POST">
{{ form.hidden_tag() }}
{{ form.name.label }} {{ form.name() }}
{{ form.submit() }}
</form>
{% if not name %}
<p>Hello, Stranger.</p>
{% else %}
<p>Hello, {{name}}</p>
{% endif %}
</body>
</html>
Part2 Flask-WTF
下面我們一起來追蹤一下程序執(zhí)行流程，重點(diǎn)關(guān)注，flask.request, session, current_app中的信息是怎么與插件交互的. 當(dāng)我們執(zhí)行完這段代碼時(shí)候（此時(shí)request還沒有到來）:
class MyForm(Form):
name = StringField("what's your name", validators=[DataRequired()])
submit = SubmitField('Submit')
實(shí)際上MyForm的metaclass（wtforms中的FormMeta類）已經(jīng)在定義類的時(shí)候干了很多事情了.具體干了哪些事呢？我們暫時(shí)只關(guān)注結(jié)果就行了. 查看MyForm.name, 和MyForm.submit中的內(nèi)容.
- MyForm.name ---> <UnboundField(StringField, ("what's your name",), {'validators': [<wtforms.validators.DataRequired object at 0x10310cc10>]})>
- MyForm.submit ---> <UnboundField(SubmitField, ('Submit',), {})>
從字面意思來理解就是未被綁定的Field.因?yàn)檫€沒有與具體的request/app中的Form進(jìn)行綁定.當(dāng)我們直接初始化form = MyForm()時(shí)， 會(huì)出現(xiàn) "RuntimeError: working outside of application context."原因在于，在flask_wtf.Form中的init函數(shù)中:
if csrf_enabled is None:
csrf_enabled = current_app.config.get('WTF_CSRF_ENABLED', True)
current_app并沒有push到Request_Context中.
下面我們?cè)诿钚兄凶鱿旅娴膶?shí)驗(yàn):
$python -i flask_wtf_demo.py
>>>#模擬"GET"方法.
>>>ctx=app.test_request_context('127.0.0.1:5000/index')
>>>form = MyForm()
>>>form.name.data # None
>>>form.validate()
False
>>>form.errors
...
>>>form.name.label()
u'<label for="name">what\'s your name</label>'
>>>form.name()
u'<input id="name" name="name" type="text" value="">'
>>>ctx.pop()
對(duì)應(yīng)到flask_wtf源碼中就是Form.init中:
if formdata is _Auto:
if self.is_submitted():
...
else:
formdata = None # <------
因?yàn)闉?GET"方法所以formdata為None.
另一個(gè)實(shí)驗(yàn),在命令行中測(cè)試"POST"方法:
>>>ctx = app.test_request_context('127.0.0.1:5000/index', method='POST', data={'name': 'saltriver'})
>>>ctx.push()
>>>form=MyForm(csrf_enabled=False)
>>>form.validate()
True
>>>form.validate_on_submit()
True
于是我們便可以對(duì)form進(jìn)行處理了.
Part 3 Redirect重定向.
@app.route('/', methods=('GET', 'POST'))
def submit():
name = None
form = MyForm()
if form.validate_on_submit():
session['name'] = form.name.data
return redirect(url_for('submit'))
return render_template('index.html', form=form, name=session.get('name'))
下面看看redirect的實(shí)現(xiàn).
