haskell - How can I branch on the value inside a Reflex Dynamic? -


in simplest case, have dynamic t bool, , when value true, want single empty div exist, , when value false, don't want there dom element.

slightly more generally, if have dynamic t (either mya myb), , have functions know how render given dynamic t mya or dynamic t myb, how call appropriate function render?

if need switch widget need 1 of:

dyn :: monadwidget t m => dynamic t (m a) -> m (event t a) source

or

widgethold :: monadwidget t m => m -> event t (m a) -> m (dynamic t a)

since you've mentioned you've got dynamic @ hand, we're gonna use dyn:

app =   switched <- button "alternate!"   flag <- folddyn ($) false (not <$ switched) -- have dynamic t bool   w <- mapdyn mywidget flag -- in latest reflex can 'fmap'   dyn w   return ()  mywidget :: monadwidget t m => bool -> m () mywidget false = blank mywidget true = el "div" $ blank

the basic rule that, due higer-order nature of reflex, if want swap-out something, need have event/dynamic yields widget value. that's why dyn takes dynamic t (m a) parameter (and appropriately, widgethold takes event t (m a). , that's why we've mapped on dynamic t bool have dynamic has our widget building action value.

it's worth mentioning, neither dynamic/widgethold virtual dom/diffing speed rendering. reflex can more explicit updates (a dynamic/event t text can affect node text directly, without rerendering whole node) , should take advantage of that. if not large portions of page swapped , can yield significant performance hit.


Comments

Post a Comment

Popular posts from this blog

php - How to add and update images or image url in Volusion using Volusion API -

actually have store importing products store product data insert , update image or image url not insert , update. this xml code name datapro.txt. <products_joined> <productcode>3710_012t</productcode> <vendor_partno>eah5450silent/di/1gd3(lp)</vendor_partno> <productname>test product ta</productname> <hideproduct>n</hideproduct> <stockstatus>20</stockstatus> <lastmodified>1/5/2016 10:25:00 am</lastmodified> <lastmodby>2</lastmodby> <productweight>0.9</productweight> <productprice>100</productprice> <productmanufacturer>asus tek</productmanufacturer> <vendor_price>32.69</vendor_price> <numproductssharingstock>0</numproductssharingstock> <categoryids>107</categoryids> <producturl>http://tebkq.mvlce.servertrust.com/productdetails.asp?productcode=3710_012t</producturl...
Read more

Laravel mail error `Swift_TransportException in StreamBuffer.php line 269: Connection could not be established with host smtp.gmail.com [ #0]` -

i developing website contact-us page guest users can send me email using gmail . anytime try send mail using contact-us form, error swift_transportexception in streambuffer.php line 269: connection not established host smtp.gmail.com [ #0] this mail.php return [ 'driver' => env('mail_driver', 'smtp'), 'host' => env('mail_host', 'smtp.gmail.com'), 'port' => 587, 'from' => ['address' => '', 'name' => ''], 'encryption' => env('mail_encryption', 'tls'), 'username' => env('mail_username'), 'password' => env(mail_password), 'sendmail' => '/usr/sbin/sendmail -bs', 'pretend' => env('mail_pretend', false), ]; this .env mail_driver=smtp mail_host=smtp.gmail.com mail_port=587 mail_username=afecjaped@gmail.com mail_password=********...
Read more

c# SetCompatibleTextRenderingDefault must be called before the first -

i tried search exception couldn't find solution on case i'am using code below invoke .net application : assembly assem = assembly.load(data); methodinfo method = assem.entrypoint; var o = activator.createinstance(method.declaringtype); method.invoke(o, null); the application invoked has form , in entrypoint of application : [stathread] static void main() { application.enablevisualstyles(); application.setcompatibletextrenderingdefault(false); //exception application.run(new form1()); } setcompatibletextrenderingdefault must called before first iwin32window object created in application. edit : assembly = assembly.load(data); methodinfo method = a.gettype().getmethod("start"); var o = activator.createinstance(method.declaringtype); method.invoke(o, null); you should create new method skips initialization...
Read more