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| -rw-r--r-- | ruby.html.markdown | 246 |
1 files changed, 120 insertions, 126 deletions
diff --git a/ruby.html.markdown b/ruby.html.markdown index 51f220e3..2f4d0934 100644 --- a/ruby.html.markdown +++ b/ruby.html.markdown @@ -16,19 +16,20 @@ contributors: - ["Persa Zula", "http://persazula.com"] - ["Jake Faris", "https://github.com/farisj"] - ["Corey Ward", "https://github.com/coreyward"] + - ["Jannik Siebert", "https://github.com/janniks"] --- ```ruby # This is a comment # In Ruby, (almost) everything is an object. -# This includes numbers… +# This includes numbers... 3.class #=> Integer -# …strings… +# ...and strings... "Hello".class #=> String -# …even methods! +# ...and even methods! "Hello".method(:class).class #=> Method # Some basic arithmetic @@ -67,7 +68,7 @@ false.class #=> FalseClass 1 != 1 #=> false 2 != 1 #=> true -# apart from false itself, nil is the only other 'falsey' value +# Apart from false itself, nil is the only other 'falsey' value !!nil #=> false !!false #=> false @@ -111,33 +112,33 @@ placeholder = 'use string interpolation' 'hello ' + 3.to_s #=> "hello 3" "hello #{3}" #=> "hello 3" -# Combine strings and operators +# ...or combine strings and operators 'hello ' * 3 #=> "hello hello hello " -# Append to string +# ...or append to string 'hello' << ' world' #=> "hello world" -# print to the output with a newline at the end +# You can print to the output with a newline at the end puts "I'm printing!" #=> I'm printing! #=> nil -# print to the output without a newline +# ...or print to the output without a newline print "I'm printing!" -#=> I'm printing! => nil +#=> "I'm printing!" => nil # Variables x = 25 #=> 25 x #=> 25 -# Note that assignment returns the value assigned -# This means you can do multiple assignment: +# Note that assignment returns the value assigned. +# This means you can do multiple assignment. x = y = 10 #=> 10 x #=> 10 y #=> 10 -# By convention, use snake_case for variable names +# By convention, use snake_case for variable names. snake_case = true # Use descriptive variable names @@ -146,7 +147,7 @@ m = '/bad/name/' # Symbols are immutable, reusable constants represented internally by an # integer value. They're often used instead of strings to efficiently convey -# specific, meaningful values +# specific, meaningful values. :pending.class #=> Symbol @@ -158,82 +159,82 @@ status == 'pending' #=> false status == :approved #=> false -# Strings can be converted into symbols and vice versa: - +# Strings can be converted into symbols and vice versa. status.to_s #=> "pending" "argon".to_sym #=> :argon # Arrays -# This is an array +# This is an array. array = [1, 2, 3, 4, 5] #=> [1, 2, 3, 4, 5] -# Arrays can contain different types of items - +# Arrays can contain different types of items. [1, 'hello', false] #=> [1, "hello", false] -# Arrays can be indexed -# From the front +# Arrays can be indexed. +# From the front... array[0] #=> 1 array.first #=> 1 array[12] #=> nil -# Like arithmetic, [var] access -# is just syntactic sugar -# for calling a method [] on an object -array.[] 0 #=> 1 -array.[] 12 #=> nil - -# From the end +# ...or from the back... array[-1] #=> 5 array.last #=> 5 -# With a start index and length +# ...or with a start index and length... array[2, 3] #=> [3, 4, 5] -# Reverse an Array +# ...or with a range... +array[1..3] #=> [2, 3, 4] + +# You can reverse an Array. a = [1,2,3] a.reverse! #=> [3,2,1] -# Or with a range -array[1..3] #=> [2, 3, 4] +# Like arithmetic, [var] access is just syntactic sugar +# for calling a method '[]' on an object. +array.[] 0 #=> 1 +array.[] 12 #=> nil -# Add to an array like this +# You can add to an array... array << 6 #=> [1, 2, 3, 4, 5, 6] # Or like this array.push(6) #=> [1, 2, 3, 4, 5, 6] -# Check if an item exists in an array +# ...and check if an item exists in an array array.include?(1) #=> true # Hashes are Ruby's primary dictionary with key/value pairs. -# Hashes are denoted with curly braces: +# Hashes are denoted with curly braces. hash = { 'color' => 'green', 'number' => 5 } hash.keys #=> ['color', 'number'] -# Hashes can be quickly looked up by key: -hash['color'] #=> 'green' +# Hashes can be quickly looked up by key. +hash['color'] #=> "green" hash['number'] #=> 5 -# Asking a hash for a key that doesn't exist returns nil: +# Asking a hash for a key that doesn't exist returns nil. hash['nothing here'] #=> nil -# When using symbols for keys in a hash, you can use this alternate syntax: +# When using symbols for keys in a hash, you can use an alternate syntax. -new_hash = { defcon: 3, action: true } +hash = { :defcon => 3, :action => true } +hash.keys #=> [:defcon, :action] -new_hash.keys #=> [:defcon, :action] +hash = { defcon: 3, action: true } +hash.keys #=> [:defcon, :action] # Check existence of keys and values in hash -new_hash.key?(:defcon) #=> true -new_hash.value?(3) #=> true +hash.key?(:defcon) #=> true +hash.value?(3) #=> true -# Tip: Both Arrays and Hashes are Enumerable -# They share a lot of useful methods such as each, map, count, and more +# Tip: Both Arrays and Hashes are Enumerable! +# They share a lot of useful methods such as each, map, count, and more. # Control structures +# Conditionals if true 'if statement' elsif false @@ -242,28 +243,26 @@ else 'else, also optional' end - +# Loops # In Ruby, traditional `for` loops aren't very common. Instead, these -# basic loops are implemented using enumerable, which hinges on `each`: - +# basic loops are implemented using enumerable, which hinges on `each`. (1..5).each do |counter| puts "iteration #{counter}" end -# Which is roughly equivalent to this, which is unusual to see in Ruby: - +# Which is roughly equivalent to the following, which is unusual to see in Ruby. for counter in 1..5 puts "iteration #{counter}" end -# The `do |variable| ... end` construct above is called a “block”. Blocks are similar +# The `do |variable| ... end` construct above is called a 'block'. Blocks are similar # to lambdas, anonymous functions or closures in other programming languages. They can -# be passed around as objects, called, or attached as methods. +# be passed around as objects, called, or attached as methods. # -# The "each" method of a range runs the block once for each element of the range. +# The 'each' method of a range runs the block once for each element of the range. # The block is passed a counter as a parameter. -# You can also surround blocks in curly brackets: +# You can also surround blocks in curly brackets. (1..5).each { |counter| puts "iteration #{counter}" } # The contents of data structures can also be iterated using each. @@ -274,8 +273,8 @@ hash.each do |key, value| puts "#{key} is #{value}" end -# If you still need an index you can use "each_with_index" and define an index -# variable +# If you still need an index you can use 'each_with_index' and define an index +# variable. array.each_with_index do |element, index| puts "#{element} is number #{index} in the array" end @@ -291,9 +290,9 @@ end #=> iteration 4 #=> iteration 5 -# There are a bunch of other helpful looping functions in Ruby, -# for example "map", "reduce", "inject", the list goes on. Map, -# for instance, takes the array it's looping over, does something +# There are a bunch of other helpful looping functions in Ruby. +# For example: 'map', 'reduce', 'inject', the list goes on. +# Map, for instance, takes the array it's looping over, does something # to it as defined in your block, and returns an entirely new array. array = [1,2,3,4,5] doubled = array.map do |element| @@ -304,6 +303,7 @@ puts doubled puts array #=> [1,2,3,4,5] +# Case construct grade = 'B' case grade @@ -322,7 +322,7 @@ else end #=> "Better luck next time" -# cases can also use ranges +# Cases can also use ranges grade = 82 case grade when 90..100 @@ -334,9 +334,9 @@ else end #=> "OK job" -# exception handling: +# Exception handling begin - # code here that might raise an exception + # Code here that might raise an exception raise NoMemoryError, 'You ran out of memory.' rescue NoMemoryError => exception_variable puts 'NoMemoryError was raised', exception_variable @@ -354,10 +354,10 @@ def double(x) x * 2 end -# Methods (and blocks) implicitly return the value of the last statement +# Methods (and blocks) implicitly return the value of the last statement. double(2) #=> 4 -# Parentheses are optional where the interpretation is unambiguous +# Parentheses are optional where the interpretation is unambiguous. double 3 #=> 6 double double 3 #=> 12 @@ -366,15 +366,14 @@ def sum(x, y) x + y end -# Method arguments are separated by a comma +# Method arguments are separated by a comma. sum 3, 4 #=> 7 sum sum(3, 4), 5 #=> 12 # yield -# All methods have an implicit, optional block parameter -# it can be called with the 'yield' keyword - +# All methods have an implicit, optional block parameter. +# Tt can be called with the 'yield' keyword. def surround puts '{' yield @@ -383,45 +382,43 @@ end surround { puts 'hello world' } -# { -# hello world -# } +#=> { +#=> hello world +#=> } - -# Blocks can be converted into a `proc` object, which wraps the block +# Blocks can be converted into a 'proc' object, which wraps the block # and allows it to be passed to another method, bound to a different scope, # or manipulated otherwise. This is most common in method parameter lists, -# where you frequently see a trailing `&block` parameter that will accept -# the block, if one is given, and convert it to a `Proc`. The naming here is -# convention; it would work just as well with `&pineapple`: +# where you frequently see a trailing '&block' parameter that will accept +# the block, if one is given, and convert it to a 'Proc'. The naming here is +# convention; it would work just as well with '&pineapple'. def guests(&block) block.class #=> Proc block.call(4) end -# The `call` method on the Proc is similar to calling `yield` when a block is -# present. The arguments passed to `call` will be forwarded to the block as arugments: +# The 'call' method on the Proc is similar to calling 'yield' when a block is +# present. The arguments passed to 'call' will be forwarded to the block as arugments. guests { |n| "You have #{n} guests." } # => "You have 4 guests." -# You can pass a list of arguments, which will be converted into an array -# That's what splat operator ("*") is for +# You can pass a list of arguments, which will be converted into an array. +# That's what splat operator ("*") is for. def guests(*array) array.each { |guest| puts guest } end # Destructuring -# Ruby will automatically destructure arrays on assignment to multiple variables: +# Ruby will automatically destructure arrays on assignment to multiple variables. a, b, c = [1, 2, 3] a #=> 1 b #=> 2 c #=> 3 # In some cases, you will want to use the splat operator: `*` to prompt destructuring -# of an array into a list: - +# of an array into a list. ranked_competitors = ["John", "Sally", "Dingus", "Moe", "Marcy"] def best(first, second, third) @@ -430,7 +427,7 @@ end best *ranked_competitors.first(3) #=> Winners are John, Sally, and Dingus. -# The splat operator can also be used in parameters: +# The splat operator can also be used in parameters. def best(first, second, third, *others) puts "Winners are #{first}, #{second}, and #{third}." puts "There were #{others.count} other participants." @@ -440,21 +437,23 @@ best *ranked_competitors #=> Winners are John, Sally, and Dingus. #=> There were 2 other participants. -# By convention, all methods that return booleans end with a question mark -5.even? # false -5.odd? # true +# By convention, all methods that return booleans end with a question mark. +5.even? #=> false +5.odd? #=> true -# And if a method ends with an exclamation mark, it does something destructive +# By convention, if a method name ends with an exclamation mark, it does something destructive # like mutate the receiver. Many methods have a ! version to make a change, and -# a non-! version to just return a new changed version +# a non-! version to just return a new changed version. company_name = "Dunder Mifflin" company_name.upcase #=> "DUNDER MIFFLIN" company_name #=> "Dunder Mifflin" -company_name.upcase! # we're mutating company_name this time! +# We're mutating company_name this time. +company_name.upcase! #=> "DUNDER MIFFLIN" company_name #=> "DUNDER MIFFLIN" +# Classes -# Define a class with the class keyword +# You can define a class with the 'class' keyword. class Human # A class variable. It is shared by all instances of this class. @@ -462,7 +461,7 @@ class Human # Basic initializer def initialize(name, age = 0) - # Assign the argument to the "name" instance variable for the instance + # Assign the argument to the 'name' instance variable for the instance. @name = name # If no age given, we will fall back to the default in the arguments list. @age = age @@ -478,10 +477,10 @@ class Human @name end - # The above functionality can be encapsulated using the attr_accessor method as follows + # The above functionality can be encapsulated using the attr_accessor method as follows. attr_accessor :name - # Getter/setter methods can also be created individually like this + # Getter/setter methods can also be created individually like this. attr_reader :name attr_writer :name @@ -496,13 +495,11 @@ class Human end end - -# Instantiate a class +# Instantiating of a class jim = Human.new('Jim Halpert') - dwight = Human.new('Dwight K. Schrute') -# Let's call a couple of methods +# You can call the methods of the generated object. jim.species #=> "H. sapiens" jim.name #=> "Jim Halpert" jim.name = "Jim Halpert II" #=> "Jim Halpert II" @@ -510,30 +507,30 @@ jim.name #=> "Jim Halpert II" dwight.species #=> "H. sapiens" dwight.name #=> "Dwight K. Schrute" -# Call the class method +# Calling of a class method Human.say('Hi') #=> "Hi" # Variable's scopes are defined by the way we name them. -# Variables that start with $ have global scope +# Variables that start with $ have global scope. $var = "I'm a global var" defined? $var #=> "global-variable" -# Variables that start with @ have instance scope +# Variables that start with @ have instance scope. @var = "I'm an instance var" defined? @var #=> "instance-variable" -# Variables that start with @@ have class scope +# Variables that start with @@ have class scope. @@var = "I'm a class var" defined? @@var #=> "class variable" -# Variables that start with a capital letter are constants +# Variables that start with a capital letter are constants. Var = "I'm a constant" defined? Var #=> "constant" -# Class is also an object in ruby. So class can have instance variables. -# Class variable is shared among the class and all of its descendants. +# Class is also an object in ruby. So a class can have instance variables. +# A class variable is shared among the class and all of its descendants. -# base class +# Base class class Human @@foo = 0 @@ -546,18 +543,17 @@ class Human end end -# derived class +# Derived class class Worker < Human end -Human.foo # 0 -Worker.foo # 0 - -Human.foo = 2 # 2 -Worker.foo # 2 +Human.foo #=> 0 +Worker.foo #=> 0 -# Class instance variable is not shared by the class's descendants. +Human.foo = 2 +Worker.foo #=> 2 +# A class instance variable is not shared by the class's descendants. class Human @bar = 0 @@ -573,8 +569,8 @@ end class Doctor < Human end -Human.bar # 0 -Doctor.bar # nil +Human.bar #=> 0 +Doctor.bar #=> nil module ModuleExample def foo @@ -582,9 +578,8 @@ module ModuleExample end end -# Including modules binds their methods to the class instances -# Extending modules binds their methods to the class itself - +# Including modules binds their methods to the class instances. +# Extending modules binds their methods to the class itself. class Person include ModuleExample end @@ -593,13 +588,12 @@ class Book extend ModuleExample end -Person.foo # => NoMethodError: undefined method `foo' for Person:Class -Person.new.foo # => 'foo' -Book.foo # => 'foo' -Book.new.foo # => NoMethodError: undefined method `foo' +Person.foo #=> NoMethodError: undefined method `foo' for Person:Class +Person.new.foo #=> "foo" +Book.foo #=> "foo" +Book.new.foo #=> NoMethodError: undefined method `foo' # Callbacks are executed when including and extending a module - module ConcernExample def self.included(base) base.extend(ClassMethods) @@ -623,10 +617,10 @@ class Something include ConcernExample end -Something.bar # => 'bar' -Something.qux # => NoMethodError: undefined method `qux' -Something.new.bar # => NoMethodError: undefined method `bar' -Something.new.qux # => 'qux' +Something.bar #=> "bar" +Something.qux #=> NoMethodError: undefined method `qux' +Something.new.bar #=> NoMethodError: undefined method `bar' +Something.new.qux #=> "qux" ``` ## Additional resources |