如何检查数据库中的现有值并更改它？

Question

我有一个表名叫“代码”和3列：ID（主），码号（串）和激活（布尔值，默认值= FALSE）

，我已经在这里我要检查值的形式，如果它存在，使其激活== False。

我想： myform.py：

#all imports here 
class CheckForm(Form): 
    some_code = StringField('Code: ',validators=[Required()]) 
    submit = SubmitField('Check it!') 

我views.py：

#all imports here 
@some.route('/sometest', methods=['GET', 'POST'] 
def check_function(): 
    form = CheckForm() 
    code=form.some_code.data 
    check_code = Codes.query.filter_by(code=code).first() 
    if check_code.activated == False: 
     check_code.activated = True 
     db.session.add(check_code) 
     db.session.commit() 
    elif check_code.activated == True: 
     print 'Code already used' 
    else: 
     print 'Code not found') 
return render_template('test.html') 

但我发现了错误：

AttributeError: 'NoneType' object has no attribute 'activated' 

我m使用烧瓶和sqlalchemy

Answer 1

只需为check_code添加一个条件，以防在数据库中找不到结果。

提示：处理上面的失败条件和从函数返回时总是更具可读性。

def check_function(): 
    form = CheckForm() 
    code=form.some_code.data 
    check_code = Codes.query.filter_by(code=code).first() 
    if not check_code: 
     print 'Code not found' 
     return # You don't have to worry about that again 

    if check_code.activated == True: 
     print 'Code already used' 
     return # Second case is already covered 

    # That's the only case left, no need for an `if` condition 
    check_code.activated = True 
    db.session.add(check_code) 
    db.session.commit()