#ruby 101

Inside a rails controller, this is how you can receive the mime type of the incoming request:

In the beginning there was nothing.

So God decided to create three different MySQL gems in order to prove all ruby developers.

1) Gem "mysql"

This is the "classical" MySQL gem. It does basically everything and it does it nicely.

Unless you hit the UTF-8 barrier.

2) Gem "mysql2"

This is the gem, which is used by Rails by default. It will do escaping, it will do UTF-8, it will do much for you.

But it is unable to do prepared statements.

3) Gem "ruby-mysql"

This is a very unknown gem, but it can do basically everything: escaping, UTF-8, prepared statements, reconnects - you name it.

If you really need all those features, I'd suggest you to give it a try. Otherwise mysql2 is the way to go.

The only problem is that its documentation is Korean. But you'll find out, that the syntax of the mysql gem simply applies.

Gaining substrings in Ruby is as easy as extracting a range of elements out of an array.

"My supercool text"[9..12]    # => "cool"

This will pick out all characters between the ninth and twelfth. 

Simultaneously, a negative end point will be handled as a negative offset.

In Ruby, there are two ways of doing if-conditions.

a) the classical if-statement b) the cool rubyish unless-statement

Both statements are the opposite of each other. But you should use both and mix 'em up, but in the right way.

Rule #1:

Don't use ever - ever - negative if-conditional statements in ruby. Because that's what unless is for.

"Yes" to this:

unless some_variable.is_a? Integer     # Unless some variable is a integer.     # Just like you'd read it. ;-) end

"Nope" to this:

if !some_variable.is_a? Integer     # Looks ugly, doesn't it? end

Rule #2:

Don't use else statements in unless-expressions.

Why? Because unless something is not something else, something else exactly ist something. Mindfuck.

Rule #3:

Use short-term conditional expressions as much as you can.

First of all, it cleans up your code.

Second: In Ruby, they are like poetry. Take a look:

return false unless my_parameter.is_a? Integer return false if my_parameter > 5

Time.now.to_i

The class method now of the class Time creates a time object, representing the current time.

In Ruby, basically everything you attach to an object is a method. There are methods, that are easy to identify as a method, like:

['This', 'is', 'crazy', 'ruby', 'syntax'].join(' ')

There are instance variables, whose you can set and get:

cool_object.variable    # => 'amazing' cool_object.variable = 'nice'

... but you are actually calling setter and getter methods:

class cool_object     def variable         return @variable    # you could drop 'return' here...     end     def variable=(value)         @variable = value     end end

There are known symbols:

packed_array[0]    # => 'cool item'

... and lesser-known symbols:

packed_array << 'new item'

... that are synonyms for

packed_array.at(0)    # => 'cool item' packed_array.push('new item')

In Ruby, you can get multiple values from an array by accessing it via a given range.

Let's take this array:

my_rocking_array = ['a', 'b', 'c', 'd', 'e', 'f', 'g']

... and return a single value:

my_rocking_array[1]   # => 'b'

... or return a range of values:

my_rocking_array[1..3]   # => ['b', 'c', 'd']

... of course, also this works:

my_rocking_array[1, 3]   # => ['b', 'c', 'd']

(0..100).to_a.sample

(0..100) creates a range of ints, which is converted into an array. Finally, sample picks out a random element of the given array.