python - What is the asterisk for in signal and slot connections? -

-

in python qt, i'm connecting qlistwidget signal slot, this:

qtcore.qobject.connect(self.mylist, qtcore.signal("itemclicked(qlistwidgetitem *)"), self.listeventhandler)

my question is: trailing asterisk in qlistwidgetitem * do?

a couple of bullet points explain (i'll try avoid c++ syntax):

  • pyqt python wrapper around qt, written in c++.
  • qt provides introspection classes inheriting qobject, using strings identify things. python has native introspection, c++ not.
  • the syntax used called "old-style signals , slots", uses c++ function signatures.
  • c++ has more types of variables python. in c++, variable can value, reference, or pointer. pointers have asterisk after type name.
  • qtcore.signal("itemclicked(qlistwidgetitem *)") refers qt signal called itemclicked has parameter pointer qlistwidgetitem, not item itself.

in c++, looks like:

 void itemclicked(qlistwidgetitem *item);

going strings introspection, identify signal or slot, drop void, ;, , variable name (item), leaving:

 itemclicked(qlistwidgetitem *)

wrap above in qtcore.signal() , pair of quotes , have:

qtcore.signal("itemclicked(qlistwidgetitem *)")

what pointer?
there number of questions this. here one number of analogies in answers simplify things you.

if old-style syntax, what's new style?
frodon bringing up. pyqt has more "pythonic" method of connecting signals slots, in format:

object.signalname.connect(otherobject.slotname)

in case:

self.mylist.itemclicked.connect(self.listeventhandler)

read more in docs.


Comments

Post a Comment

Popular posts from this blog

java - Suppress Jboss version details from HTTP error response -

-
my jboss verson jboss eap 6.3 when kind of error response sent jboss, adds server information response. following sample row response: http/1.1 400 bad request server: apache-coyote/1.1 content-type: text/html;charset=utf-8 content-length: 2391 date: tue, 19 jul 2016 09:30:46 gmt connection: close jboss web/7.4.8.final-redhat-4 - jbweb000064: error report jbweb000065: http status 400 - org.codehaus.jackson.map.jsonmappingexception: can not construct instance of mybean.type string value 'xyz': value not 1 of declared enum instance names @ [source: org.jboss.resteasy.core.interception.messagebodyreadercontextimpl$inputstreamwrapper@5e421c2b; line: 14, column: 26] (through reference chain: requestargs["request"]) jbweb000309: type jbweb000067: status report jbweb000068: message org.codehaus.jackson.map.jsonmappingexception: can not construct instance of mybean.type string value 'xyz': value not 1 of declared enum instance names @ [source: org.jboss...
Read more

gridview - Yii2 DataPorivider $totalSum for a column -

-
i have order , ordersearch models. in order list (actionindex) gridview there filtering , sorting. on of columns in order order_total (sum of products in order). i need implement sum of order_total in gridview. if manually counting activedataprovider->getmodels() array_map spend 3 seconds 3000 orders (localhost). don't want miss time. i see 2 ways make faster: create cache every filter , update lifetime (horrible) the interesting can right in ordersearch->search() method $query method. don't understand how can pass in controller. example of code 2nd way: class ordersearch extends order { public $totalsum; public function search($params) { $query = order::find(); $dataprovider = new activedataprovider([ 'query' => $query, ]); $this->load($params); $this->totalsum = $query->sum('order_total'); // works fast return $dataprovider; } } after i...
Read more

Sass watch command compiles .scss files before full sftp upload -

-
i use winscp download , edit .scss files , sass on linux (on server) compile them .css . after saving file, use: sass scss/style.scss css/style.css , replaces css file compiled sccs. the problem i want skip part return command line after editing scss file, sake of automation , saving time. but, if use watch command: sass --watch scss/style.scss:css/style.css synchronize 2 files, alerts nonexistent css errors pop up: change detected to: scss/style.scss error scss/style.scss (line 232: invalid css after "...ht: bold; line-": expected "{", "") note that when file uploads quicker usual (sometimes happens) watch command job, no errors. this because, when file upload takes time, sass compiles scss file (on server) before uploaded remote folder. thus, compiles part of file, resulting in css errors. is there way set timer watch command waits few seconds after detects changes , before compiling? any other way overcome is, of course, ...
Read more