django - 保存前比较旧的和新的字段值 [英] django - comparing old and new field value before saving
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问题描述
我尝试过save()的继承,并且pre_save信号。它被正确触发,但是找不到实际更改字段的列表,无法比较旧值和新值。有办法吗我需要它来优化预设动作。
谢谢!
解决方案
p>有一个非常简单的django方式来执行。
记住模型init中的值,如下所示:
$ _ code def __init __(self,* args,** kwargs):
super(MyClass,self).__ init __(* args,** kwargs)
self .initial_parametername = self.parametername
---
self.initial_parameternameX = self.parameternameX
现实生活中的例子:
在上课时:
def __init __(self,* args,** kwargs):
super(MyClass,self).__ init __(* args,** kwargs)
self .__ important_fields = ['target_type','target_id' $ object_object','number','chain','expiration_date']
for self .__ important_fields:
setattr(self,'__original_%s'%field,getattr(self,field))
def has_changed(self):
对于自己的字段.__ important_fields:
orig ='__original_%s'%field
if getattr(self,orig)!= getattr(self,field):
return True
返回False
然后在模型保存方法中:
$ save $($)
$ b obj = super(MyClassForm,self)$ $ $ $ $ $ $ $ $ $ $ $ $ $))))))))))))))))))))))))))))) .save(commit = False)
如果obj.has_changed():
#如果我们用承诺失败,保存这个狗屎
如果提交:
obj.save(force_insert = True)
return obj
I have a django model, and I need to compare old and new values of field BEFORE saving.
I've tried the save() inheritence, and pre_save signal. It was triggered correctly, but I can't find the list of actualy changed fields and can't compare old and new values. There is a way? I need it for optimization of presave actions.
Thank you!
解决方案
There is very simple django way for doing it.
"Memorise" the values in model init like this:
def __init__(self, *args, **kwargs):
super(MyClass, self).__init__(*args, **kwargs)
self.initial_parametername = self.parametername
---
self.initial_parameternameX = self.parameternameX
Real life example:
At class:
def __init__(self, *args, **kwargs):
super(MyClass, self).__init__(*args, **kwargs)
self.__important_fields = ['target_type', 'target_id', 'target_object', 'number', 'chain', 'expiration_date']
for field in self.__important_fields:
setattr(self, '__original_%s' % field, getattr(self, field))
def has_changed(self):
for field in self.__important_fields:
orig = '__original_%s' % field
if getattr(self, orig) != getattr(self, field):
return True
return False
And then in modelform save method:
def save(self, force_insert=False, force_update=False, commit=True):
# Prep the data
obj = super(MyClassForm, self).save(commit=False)
if obj.has_changed():
# If we're down with commitment, save this shit
if commit:
obj.save(force_insert=True)
return obj
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