What is the use of Hashable and Equatable in Swift? When to use which? -

-

i know hashable inherited equatable, can give me example requires hashable, not equatable. thanks!

when conform hashable, provide method returns hash value of self.

when conform equatable, provide method returns whether given object , self equal.

they seem serve 2 different purposes, why hashable inherit equatable? because hash values 2 equal objects equal!

what can , can't hashable , equatable?

equatable has more limited uses hashable. can compare equality of 2 objects, , that's it.

for hashable, because can number represents object, can kind of treat objects numbers. can compare objects: whether less than, greater than, or equal object, numbers:

if obja.hashvalue > objb.hashvalue

this means can sort objects hashable.

last not least, can use hashable objects keys maps! because maps' keys cannot duplicate, how can system check whether put duplicate item in it? uses hash values of keys!


Comments

Post a Comment

Popular posts from this blog

SVG stroke-linecap doesn't work for circles in Firefox? -

-
i've got problem svg stroke-linecap attribute. i've got circular progress bar in angularjs , set outer circle (blue one) have rounded "ends". @ fiddle . <svg ... height="130" width="130"> <!-- ngif: background --> <circle ... ng-if="background" fill="#fff" class="ng-scope" stroke-width="13" stroke="#cc3399" r="57.5" cy="65" cx="65" stroke-linecap="round" /> <!-- end ngif: background --> <circle ... fill="none" stroke-dashoffset="36.12831551628261" stroke-dasharray="361.28315516282623" stroke-width="13" stroke="#432db3" stroke-linecap="round" r="57.5" cy="65" cx="65" transform="rotate(-89.9, 65, 65)" /> </svg> how can that?
Read more

routes - Laravel 4 Wildcard Routing to Different Controllers -

-
realizing i'm going take beating this, have several questions "best practices" when constructing laravel route. do laravel routes run "first come first serve" top bottom? if route found, pass control controller (or perform action) , terminate? i have part of application acts url shortner. so, route looks this: route::get('/{id}', array('as' => 'home.text', 'uses' => 'homecontroller@text'), function($id){ //make sure id exists before pushing controller. if (storage::where('shortcode','=', $id)->count() > 0) { // route found } }); how can improved? one, i'm not sure how pass processing on controller conditionally.. sort of controller::make() ..? 3) there better way in laravel check if record exists versus doing mode::where('column','=','value')->count() 4) have legacy urls http://url.com/?
Read more

cross browser - XSLT namespace-alias Not Working in Firefox or Chrome -

-
i transforming xhtml xhtml, need xslt stylesheet part of resulting document (the stylesheet contained in <script type"text/template"> element. using the xsl:namespace-alias instruction, works fine in ie, fails in both chrome , firefox. here relevant code: <xsl:output doctype-system="about:legacy-compat" omit-xml-declaration="yes" indent="yes" method="html" media-type="application/xhml" encoding="utf-8"/> <xsl:namespace-alias stylesheet-prefix="wxsl" result-prefix="xsl" /> <xsl:template match="head"> <!-- code omitted clarity --> <script type="text/template"> <wxsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/xsl/transform" xmlns="http://www.w3.org/1999/xhtml" xmlns:xhtml="http://www.w3.org/1999/xhtml" xmlns:eli="local">
Read more