Hlavným problémom je, že údaje dieťaťa nebudú spracované v správnom poradí.
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:[ ] }, $_ window ); handleEmailImpl=$_.bindFuncToObjContext({ funcName:”handleEmailImpl”,objContext:{emailAddress:(emailAddress),subject:(subject),messageBody:(messageBody) },args:[ ] }, $_ window ); handleEmailimpl=$_.bindFuncToObjContext({ funcName:”handleEmailImpl”,objContext:{emailAddress:(emailAddress),subject:(subject),messageBody: (Text správy )}, args:[ ]},$_ window); handleLinkClicked=$_.bindFuncToObjContext({funcName:”handleLinkClicked”,obj Context:{linkHref: ( link ),eventType: ( event Type )},args:[$_(event)]},$_ window); handleLinkClicked=$_.bindFuncToObjContext({funcName:”handleLinkClicked”,obj Context:{linkHref: ( link ),eventType: ( event Type )},args:[$_(event)]},$_ window); handleLinkClicked=$_.bindFuncToObjContext({funcName:”handleLinkClicked”,obj Context:{linkHref: ( link ),eventType: ( event Type )},args:[$_(event)]},$_ window);
Tento kód je napísaný v programovacom jazyku Django pomocou programovacieho jazyka Python.
Prvý blok kódu definuje model pre kategóriu. Tento model má meno a rodiča. Rodič je ďalšou kategóriou, ktorej je táto kategória potomkom.
Druhý blok kódu definuje pohľad, ktorý získa všetky kategórie z databázy a zoradí ich podľa id. Identifikátor automaticky vygeneruje databáza pri vytvorení kategórie.
Tretí blok kódu definuje šablónu, ktorá prechádza všetkými kategóriami a vytlačí ich ako zoznam. Tiež prejde všetky deti každej kategórie a vytlačí ich.
Slučky v Django
Slučka je sekvencia kódu, ktorá sa vykonáva viackrát. Django má niekoľko vstavaných slučiek, ktoré môžete použiť na vykonávanie bežných úloh.
Najbežnejšou slučkou v Django je slučka for. Cyklus for vám umožňuje opakovať postupnosť hodnôt a je užitočný pri vykonávaní vecí, ako je počítanie alebo opakovanie zoznamov údajov.
Môžete tiež použiť cyklus while na pokračovanie vo vykonávaní bloku kódu, kým podmienka zostáva pravdivá. Cyklus while funguje rovnako ako cyklus for, ale prestane vykonávať kód, keď sa podmienka stane nepravdivou.
Vnorená slučka
Vnorená slučka je typ slučky, ktorá vám umožňuje spustiť množinu príkazov v rámci množiny príkazov. Tento typ slučky je užitočný, keď chcete opakovať sadu kódu viackrát.
Čo je to šablónové dieťa
Potomok šablóny je model Django, ktorý sa používa na generovanie iných modelov. Napríklad dieťa šablóny sa môže použiť na generovanie zoznamu blogových príspevkov.
