Today I learned

[willkuns-blog]

How to compare two Enumerables in C#

Using Enumerable.SequenceEqual. It will compare two Enumerables and will only return true if they are exactly the same. It can be used as a method of an Enumerable or as a static method of the Enumerable class.

int[] a = { 1, 2, 3 }; int[] b = { 1, 2, 3 }; int[] c = { 3, 2, 1 }; a.SequenceEqual(b); //true Enumerable.SequenceEqual(a, b); //true Enumerable.SequenceEqual(b, c); //false

[willkuns-blog]

How to loop in Velocity Template Language

Using #foreach(). It works on Collections, Arrays, Enumerators, Maps and Iterators. Since velocity doesn't support any other kind of loop, you can use the variable $velocityCount to check the index of the current loop.

#foreach( $product in $allProducts ) Item #$velocityCount: $product #end

[willkuns-blog]

How to create an abstract class in Sass

Using the placeholder selectors. Use it just like a class but replace the "."with a "%". This way, the rules won't show up in the compiled css unless they're used with @extend. 

%foo { color: #fff; } .bar { @extend %foo; }

[willkuns-blog]

How to convert an Array to a List in Java

Using Arrays.asList. It's a static method and can't be used with Arrays of primitive types (create the array with the primitive wrapper types instead)

List values = Arrays.asList("foo", "bar", "baz");

[willkuns-blog]

How to change rubygems source

Using gem sources. Windows sometimes has ssl problems when installing a gem. In order to fix it, change the source from https to http by removing the original source and adding a new one.

$ gem sources -r https://rubygems.org/ $ gem sources -a http://rubygems.org/

[willkuns-blog]

How to trim strings in Ruby

Using the strip method. To remove only leading space, one can use lstrip and for trailing space rstrip (duh!)

str = ' This is a string ' str.strip #returns 'This is a string' str.lstrip #return 'This is a string ' str.rstrip #return ' This is a string'

[willkuns-blog]

How to add a custom 404 page to a Sinatra app

Using the not_found handler. The block you define will be called whenever Sinatra can't find a page.

not_found do haml :notfound end

[willkuns-blog]

How to add a second remote to a git project

Using remote add . The syntax is as simple as this:

$ git remote add [remote-name] [url-to-your-repo]

[willkuns-blog]

How to get the name of the currently executed method in Ruby

Using __method__. It returns nil if called outside a method.

[willkuns-blog]

How to style the text selection of an input

Using the ::selection pseudo-class. It's not a standard (meaning browser may or may not support it) and only a small subset of css is applicable to it, but you can still do some things with it. Here's a snippet:

::selection { color: white; background: black; }

On top of changin the colors, you can also change the cursor, outline, text-decoration, text-emphasis-color and text-shadow properties. For use on firefox, don't forget to add the -moz- prefix (::-moz-selection)

[willkuns-blog]

How to create a ssh key

Using the ssh-keygen. All you have to do is run this script and let the magic happen:

ssh-keygen -t rsa -C "[email protected]"

[willkuns-blog]

How to enable Integer Overflow checking on C#

Using the checked keyword. It can be used as an expression or a block and, in both cases, will throw an OverflowException if the result of an expression is greater than int.MaxValue.

int a = 0, b = 0, c = 0; try { a = 10; b = a + 2147483647 c = checked(a + 2147483647) } catch(OverflowException e) { Console.WriteLine("Overflow Exception!") } Console.WriteLine("a: {0}, b: {1}, c: {2}", a, b, c)

The last line will output "a: 10, b: -2147483639, c: 0". It's so because the value of b wrapped around to a negative value, while c never gets a new value because the checked keyword throws an error.

[willkuns-blog]

How to send emails in Node.js

Using emailjs. The whole thing is so simple you can set it up in under one minute. Simply install emailjs on you project:

npm install emailjs

To send your emails you just need the following lines:

var email = require('emailjs'), server, message; server = email.server.connect({ user: '[email protected]', password:'mypassword', host: 'smtp-mail.outlook.com', tls: { ciphers: 'SSLv3' } }); message = { subject: 'With love', from: '[email protected]', to: '[email protected]', text: 'It works!' }; server.send(message, function(err, message) { console.log(err || message); });

It also supports attachments and html, so it'll probably suit all your email needs.

[willkuns-blog]

How to create first-class citizen functions in Ruby

Using Proc. Unlike a block, an instance of Proc is an object. That means functions created using the Proc constructor can be stored in variables for reuse, for example. The syntax is as follows:

f = Proc.new{ puts 'Hello World!' } f.call

Other possible ways of creating a Proc are using the lambda keyword or the -> operator (called Proc literal, by the way), like this:

f = lambda { puts 'Hello World!' } g = -> { puts 'Hello World!' }

Procs created using lambda or -> behave just the same. A nice list of the differences between a Proc created with the constructor and one created with the literal syntax can be found here.

[willkuns-blog]

How to use pseudo-classes inside nested rules in Sass

Using the parent selector. When nesting rules, you can refer to the parent rule by using an & (ampersand). The & is basically a placeholder, so when compiling to css all instances of & will be replaced with the name of the parent. The following Sass code:

.some-class a text-decoration: none &:hover color: #1e1e1e .some-other-class & text-decoration: underline

Compiles into the following CSS:

.some-class a { text-decoration: none; } .some-class a:hover { color: #1e1e1e; } .some-other-class .some-class a { text-decoration: underline; }

[willkuns-blog]

How to edit the hosts file of a Mac

Open the file using vi (requires administrator password)

sudo vi /private/etc/hosts

Press i to enter the insert mode. Make the changes you need and then press esc to exit insert mode. To save the file, type :wq and hit return.

[willkuns-blog]

How to make a cellphone vibrate using JavaScript

Using the Vibration API. Even though it is still not fully standardized, Firefox 11+ and Chrome (both for mobile) already support it. Internet Explorer's implementation is under consideration. Its use is very simple:

//Verify the existence of the vibrate function if(Modernizr.vibrate) { //Vibrates for one second window.navigator.vibrate(1000); //Vibrates for one, two and then three seconds, with short pauses between each vibration window.navigator.vibrate([1000, 2000, 3000]); } else { //No support yet, try using other browser }

Two other things are also worth mentioning:

The vibrate function returns a boolean that indicates whether it was executed correctly or not.

When you call the vibrate function and the device is still vibrating from a previous call, the new call will halt the previous one. It means that calling the vibrate function and passing it a 0 will make the device stop vibrating, so it can be used to implement a "stopVibration" sort of function.