from<\/span> django<\/span> import<\/span> template<\/span> # to handle templates variables and context<\/span><\/div>register<\/span> =<\/span> template<\/span>.<\/span>Library<\/span>()<\/span> # register our template tags to be able to use them in our templates<\/span><\/div> <\/div>
from<\/span> events<\/span> import<\/span> models<\/span> # to get the models of our app<\/span><\/div> <\/div>
class<\/span> EventMetadataListNode<\/span>(<\/span>template<\/span>.<\/span>Node<\/span>):<\/span><\/div> def<\/span> __init__<\/span>(<\/span>self<\/span>,<\/span> event_pk<\/span>,<\/span> context_var<\/span>):<\/span><\/div> self<\/span>.<\/span>context_var<\/span> =<\/span> context_var<\/span> # new var we are going to create<\/span><\/div> self<\/span>.<\/span>event_pk<\/span> =<\/span> template<\/span>.<\/span>Variable<\/span>(<\/span>event_pk<\/span>)<\/span> # the pk, get from the template "context" as a variable<\/span><\/div> <\/div>
def<\/span> render<\/span>(<\/span>self<\/span>,<\/span> context<\/span>):<\/span><\/div> # here we create a new context variable named from self.context_var and assign to it the result set<\/span><\/div> # see the use of "resolve" that will get us the var from the context<\/span><\/div> context<\/span>[<\/span>self<\/span>.<\/span>context_var<\/span>]<\/span> =<\/span> models<\/span>.<\/span>EventMetadata<\/span>.<\/span>objects<\/span>.<\/span>filter<\/span>(<\/span>event__pk<\/span>=<\/span>self<\/span>.<\/span>event_pk<\/span>.<\/span>resolve<\/span>(<\/span>context<\/span>))<\/span><\/div> return<\/span> ''<\/span><\/div> <\/div>
def<\/span> do_get_event_metadata<\/span>(<\/span>parser<\/span>,<\/span> token<\/span>):<\/span><\/div> """<\/span><\/div> get the event metadata<\/span><\/div> <\/div>
Example::<\/span><\/div> {% get_event_metadata event.pk as metadatas %}<\/span><\/div> """<\/span><\/div> # split the args string, it detects "quoted parameters" and doesn't stop on spaces<\/span><\/div> bits<\/span> =<\/span> token<\/span>.<\/span>split_contents<\/span>()<\/span><\/div> if<\/span> len<\/span>(<\/span>bits<\/span>)<\/span> !=<\/span> 4<\/span>:<\/span> # we check if we passed the right number of args<\/span><\/div> raise<\/span> template<\/span>.<\/span>TemplateSyntaxError<\/span>(<\/span>_<\/span>(<\/span>'<\/span>%s<\/span> tag requires exactly 1 argument, and a variable'<\/span>)<\/span> %<\/span> bits<\/span>[<\/span>0<\/span>])<\/span><\/div> <\/div>
return<\/span> EventMetadataListNode<\/span>(<\/span>bits<\/span>[<\/span>1<\/span>],<\/span> bits<\/span>[<\/span>3<\/span>])<\/span> # bits[1] == events.pk, bits[3] == variable<\/span><\/div> <\/div>
# finally we register the new template tag<\/span><\/div># first parameter is the name in the template the second one is the name in the source file<\/span><\/div>register<\/span>.<\/span>tag<\/span>(<\/span>'get_event_metadata'<\/span>,<\/span> do_get_event_metadata<\/span>)<\/span><\/div><\/pre><\/div>\n \n <\/div>\n\n