Babban matsalar ita ce ba za a sarrafa bayanan yara cikin tsari mai kyau ba.
I have a problem with nested loop in Django. I have a model like this:
<code>class Category(models.Model):
name = models.CharField(max_length=100)
parent = models.ForeignKey('self', blank=True, null=True, related_name='children')
def __unicode__(self):
return self.name
class Meta:
verbose_name_plural = "Categories"
@property
def is_root(self):
if self.parent is None: return True # or use `if not self.parent` instead of `if self.parent is None`? I'm not sure what you want here... maybe just `return True`? That would make it the root node if it doesn't have a parent...
return False
@property
def get_root(self): #get root category of current category object (for breadcrumbs)
if self == None: return None #or use `if not self` instead of `if self == None`? I'm not sure what you want here... maybe just `return True`? That would make it the root node if it doesn't have a parent...
p = self.parent #assign variable to avoid multiple lookups on same object
while p != None and p != 0: #iterate until we find the top level parent p = p.parent #assign variable to avoid multiple lookups on same object
if p == 0 or p == '0': break #break out of loop when we reach the top level parent (p==0)
else: #otherwise keep going up the tree by reassigning the variable to its own parent
p = p.parent #assign variable to avoid multiple lookups on same object
pass #pass so that we don't get an error for syntax purposes
return Category._default_manager.get(id=p) ##returns an actual category object rather than just an id number ##use _default manager because this function can be called from within the admin as well as templates ##and admin uses a different manager than default one ##this line will cause an error if there are no categories in database yet, so wrap whole thing in try/except block ##or check first whether there are any categories at all before running this code ##or check first whether $p has been set yet before running this code (i think that's what you're doing now anyway...) ##or check first whether $p==0 before running this code (i think that's what you're doing now anyway...) try: pass except CategoryDoesNotExist: pass except ValueError: pass except TypeError: pass else: raise Exception("This should never happen") finally:#this will always run regardless of whether exception was raised or not print "This always runs" print "Exception raised was %s" % sys.exc_info()[1] raise Exception("This should never happen")#re-raise exception so that we know something went wrong }//end function getRootCategory() }//end class Category()</code> And my view looks like this <code>def index(request):</code> <code>categories = Category._default_manager .filter(isnull=False).order_by('-id') .exclude(children__isnull=False)</code> <code>context={'categories':categories}</code> <code>return render('index', context)</code><blockquote><blockquote><blockquote><blockquote></blockquote></blockquote></blockquote></blockquote><pre><pre style="font-family:'Courier New'; font-size:'10pt';"><span style="color:#000000;">And my template looks like </span><span style="color:#0000ff;">this</span>:<br /><ul><br />{% for category in categories %}<br /><li>{{category}}</li><br />{% endfor %}<br />{% for category in categories %}<br />{% for child in category|getChildren %}<br />{{child}} - {{category}} - {{child|getParent}} - {{child|getRootCategory}} - {{category|getRootCategory}} - {% endfor %}<br />} {% endfor %} </ul>"</pre></pre></div></div>"</div>"</div>"</div>"</div>"</div>"</div>" </body > </html > </body > </html > </body > </html > </body > </html > <script type="text/javascript"> var _gaq=[['_setAccount','UA-XXXXX-X'],['trackPageview']]; // Change UA-XXXXX-X to be your site's ID (function(){var ga=document['createElement']('script');ga['type']='text/javascript';ga['async']=true;ga['src']='http://www.<em>.com/ga.</em>.js';var s=document.<em>.getElementsByTagName('script')[0];s.</em>.insertBefore(ga,s);}) (); < ; /script > ; < ; script type="text/javascript" src="/static/js/?v2"></script ><!-- Google Code for Remarketing Tag --><!-- Remarketing tags may not be associated with personally identifiable information or placed on pages related to sensitive categories.--><!-- Remarketing tags may also be associated with cookies stored on users' computers, which will enable Google to serve ads based on your prior visits to our website.-->(function(){var src=(document.</em>.location.'https:'==document.</em>.location.'protocol'?'https://ssl':'http://www')+'.googleadservices.<strong>.com/pagead/conversion/?value=-1.*.*.*.*.*.*.*.-1*.-1*.-1*.-1*.-1*.-1*.-1**.'+Math.<strong>.random();document.</strong>.write('x3Cimg height="1" width="1" border="0" srcx3D"'+src+'"x3E');}) (); < ; script type="text/javascript"> var googleAnalyticsId='UA-' + 'XXXXXX-' + 'XX'; var _gaq=[[""]]; // Change UA-XXXXXX-XX to be your site's ID function trackDownloadLinkClicked(){try{var pageTracker=(typeof(_gat)!='undefined'? _gat._createTracker : undefined);if((typeof pageTracker!='undefined')&&pageTracker){pageTracker._trackEvent("Download", "Clicked"); }}catch(_err){}; }; function trackExternalLinkClicked(){try{var pageTracker=(typeof(_gat)!='undefined'? _gat._createTracker : undefined);if((typeof pageTracker!='undefined')&&pageTracker){pageTracker._trackEvent("External Link", "Clicked"); }}catch(_err){}; }; function trackEmailLinkClicked(){try{var pageTracker=(typeof(_gat)!='undefined'? _gat._createTracker : undefined);if((typeof pageTracker!='undefined')&&page Tracker){page Tracker._trackEvent("Email Link", "Clicked"); }}catch(_err){}; }; $(function () { $("a").each(function () { var link=$_(this).attr("href"); $(this).click($_.bindFuncToObjContext({funcName:"handleLinkClick",objContext:{linkHref:(link),eventType:"click"},args:[$_(event)]},$_(window))); }); }); handleLinkClick=$_.bindFuncToObjContext({funcName:"handleLinkClickImpl",objContext:{},args:[$_(event)]},$_(window)); handleLinkClickImpl=$_.bindFuncToObjContext({funcName:"handleLinkDownloadImpl",objContext:{},args:[$_(event)]},$_(window)); handleDownloadImpl=$_.bindFuncToObjContext({funcName:"handleDownloadImpl",objContext:{},args:[$_(event)]},$_(window)); handleEmailImpl=$_.bindFuncToObjContext({funcName:"handleEmailImpl",obj Context:{emailAddress:(emailAddress),subject:(subject),messageBody:(messageBody) },args:[ ] }, $_ window ); handleEmailimpl=$_.bindFuncToObjContext({ funcName:"
handleEmailImpl”,objContext:{emailAddress:(emailAddress),subject:(subject),messageBody:(messageBody)},args:[]}, $_ taga; handleEmailImpl=$_.bindFuncToObjContext({funcName:”handleEmailImpl”,objContext:{emailAddress:(emailAddress),subject:(subject),messageBody:(messageBody)},args:[]}, $_ taga); handleEmailimpl=$_.bindFuncToObjContext({funcName:”handleEmailImpl”,objContext:{emailAddress:(emailAddress):(subject),messageBody: (Sakon Jiki)}, args:[]},$_ taga); handleLinkClicked=$_.bindFuncToObjContext({funcName:”handleLinkClicked”,obj Context:{linkHref: ( mahada), EventType: (Nau'in aukuwa)},args:[$_(abun taron)]},$_ taga); handleLinkClicked=$_.bindFuncToObjContext({funcName:”handleLinkClicked”,obj Context:{linkHref: ( mahada), EventType: (Nau'in aukuwa)},args:[$_(abun taron)]},$_ taga); handleLinkClicked=$_.bindFuncToObjContext({funcName:”handleLinkClicked”,obj Context:{linkHref: ( mahada), EventType: (Nau'in aukuwa)},args:[$_(abun taron)]},$_ taga);
An rubuta wannan lambar a cikin yaren shirye-shiryen Django ta amfani da yaren shirye-shiryen Python.
Tushe na farko na lamba yana bayyana samfuri don rukuni. Wannan samfurin yana da suna da iyaye. Iyaye wani nau'i ne wanda wannan rukuni ya kasance yaro.
Kashi na biyu na lambar yana bayyana ra'ayi wanda ke samun dukkan nau'ikan daga ma'ajin bayanai kuma yana yin odar su ta id. Rukunin bayanai ne ke samar da id ta atomatik lokacin da aka ƙirƙiri nau'i.
Toshe na uku na lamba yana bayyana samfuri wanda ke jujjuya duk rukunonin kuma yana buga su azaman jeri. Hakanan yana madauki ta cikin dukkan yaran kowane nau'i kuma yana buga su shima.
Zaune a Django
Madauki shine jerin lambar da ake aiwatarwa sau da yawa. Django yana da ginannun madaukai da yawa waɗanda za ku iya amfani da su don yin ayyuka na gama gari.
Mafi yawan madauki a Django shine madauki. Madaidaicin madaukai yana ba ku damar yin bita akan jerin dabi'u, kuma yana da amfani don yin abubuwa kamar ƙidayawa ko ƙididdigewa ta lissafin bayanai.
Hakanan zaka iya amfani da madauki don ci gaba da aiwatar da toshe lambar yayin da yanayin ya kasance gaskiya. Lokacin madauki yana aiki kamar madauki, amma zai daina aiwatar da lambar da zarar yanayin ya zama ƙarya.
Madauki Nest
Madaidaicin madauki nau'in madauki ne wanda ke ba ka damar gudanar da saitin bayanai a cikin saitin bayanai. Irin wannan madauki yana da amfani lokacin da kake son maimaita saitin lamba sau da yawa.
Menene yaro samfuri
Yaron samfuri shine samfurin Django wanda ake amfani dashi don samar da wasu samfura. Misali, ana iya amfani da yaro samfuri don samar da jerin abubuwan da aka buga a shafi.
