diff options
Diffstat (limited to 'ruby.html.markdown')
| -rw-r--r-- | ruby.html.markdown | 145 |
1 files changed, 83 insertions, 62 deletions
diff --git a/ruby.html.markdown b/ruby.html.markdown index e0a6bb6e..bbc8c558 100644 --- a/ruby.html.markdown +++ b/ruby.html.markdown @@ -15,32 +15,28 @@ contributors: - ["Gabriel Halley", "https://github.com/ghalley"] - ["Persa Zula", "http://persazula.com"] - ["Jake Faris", "https://github.com/farisj"] + - ["Corey Ward", "https://github.com/coreyward"] --- ```ruby # This is a comment -=begin -This is a multiline comment -No-one uses them -You shouldn't either -=end +# In Ruby, (almost) everything is an object. +# This includes numbers… +3.class #=> Integer -# First and foremost: Everything is an object. - -# Numbers are objects - -3.class #=> Fixnum - -3.to_s #=> "3" +# …strings… +"Hello".class #=> String +# …even methods! +"Hello".method(:class).class #=> Method # Some basic arithmetic 1 + 1 #=> 2 8 - 1 #=> 7 10 * 2 #=> 20 35 / 5 #=> 7 -2**5 #=> 32 +2 ** 5 #=> 32 5 % 3 #=> 2 # Bitwise operators @@ -52,6 +48,7 @@ You shouldn't either # for calling a method on an object 1.+(3) #=> 4 10.* 5 #=> 50 +100.methods.include?(:/) #=> true # Special values are objects nil # equivalent to null in other languages @@ -72,9 +69,10 @@ false.class #=> FalseClass # apart from false itself, nil is the only other 'falsey' value -!nil #=> true -!false #=> true -!0 #=> false +!!nil #=> false +!!false #=> false +!!0 #=> true +!!"" #=> true # More comparisons 1 < 10 #=> true @@ -82,7 +80,8 @@ false.class #=> FalseClass 2 <= 2 #=> true 2 >= 2 #=> true -# Combined comparison operator +# Combined comparison operator (returns `1` when the first argument is greater, +# `-1` when the second argument is greater, and `0` otherwise) 1 <=> 10 #=> -1 10 <=> 1 #=> 1 1 <=> 1 #=> 0 @@ -90,7 +89,6 @@ false.class #=> FalseClass # Logical operators true && false #=> false true || false #=> true -!true #=> false # There are alternate versions of the logical operators with much lower # precedence. These are meant to be used as flow-control constructs to chain @@ -101,23 +99,17 @@ do_something() and do_something_else() # `log_error` only called if `do_something` fails. do_something() or log_error() - -# Strings are objects - -'I am a string'.class #=> String -"I am a string too".class #=> String +# String interpolation placeholder = 'use string interpolation' "I can #{placeholder} when using double quoted strings" #=> "I can use string interpolation when using double quoted strings" -# Prefer single quoted strings to double quoted ones where possible -# Double quoted strings perform additional inner calculations - -# Combine strings, but not with numbers +# You can combine strings using `+`, but not with other types 'hello ' + 'world' #=> "hello world" 'hello ' + 3 #=> TypeError: can't convert Fixnum into String 'hello ' + 3.to_s #=> "hello 3" +"hello #{3}" #=> "hello 3" # Combine strings and operators 'hello ' * 3 #=> "hello hello hello " @@ -150,9 +142,8 @@ snake_case = true # Use descriptive variable names path_to_project_root = '/good/name/' -path = '/bad/name/' +m = '/bad/name/' -# Symbols (are objects) # Symbols are immutable, reusable constants represented internally by an # integer value. They're often used instead of strings to efficiently convey # specific, meaningful values @@ -167,6 +158,11 @@ status == 'pending' #=> false status == :approved #=> false +Strings can be converted into symbols and vice versa: + +status.to_s #=> "pending" +"argon".to_sym #=> :argon + # Arrays # This is an array @@ -196,7 +192,7 @@ array.last #=> 5 array[2, 3] #=> [3, 4, 5] # Reverse an Array -a=[1,2,3] +a = [1,2,3] a.reverse! #=> [3,2,1] # Or with a range @@ -223,7 +219,7 @@ hash['number'] #=> 5 # Asking a hash for a key that doesn't exist returns nil: hash['nothing here'] #=> nil -# Since Ruby 1.9, there's a special syntax when using symbols as keys: +# When using symbols for keys in a hash, you can use this alternate syntax: new_hash = { defcon: 3, action: true } @@ -246,33 +242,26 @@ else 'else, also optional' end + +# In Ruby, traditional `for` loops aren't very common. Instead, these +# 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: + for counter in 1..5 puts "iteration #{counter}" end -#=> iteration 1 -#=> iteration 2 -#=> iteration 3 -#=> iteration 4 -#=> iteration 5 -# HOWEVER, No-one uses for loops. -# Instead you should use the "each" method and pass it a block. -# A block is a bunch of code that you can pass to a method like "each". -# It is analogous to lambdas, anonymous functions or closures in other -# programming languages. +# 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. # # 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. -# Calling the "each" method with a block looks like this: - -(1..5).each do |counter| - puts "iteration #{counter}" -end -#=> iteration 1 -#=> iteration 2 -#=> iteration 3 -#=> iteration 4 -#=> iteration 5 # You can also surround blocks in curly brackets: (1..5).each { |counter| puts "iteration #{counter}" } @@ -365,10 +354,10 @@ def double(x) x * 2 end -# Methods (and all 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 result is unambiguous +# Parentheses are optional where the interpretation is unambiguous double 3 #=> 6 double double 3 #=> 12 @@ -399,25 +388,57 @@ surround { puts 'hello world' } # } -# You can pass a block to a method -# "&" marks a reference to a passed 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`: def guests(&block) - block.call 'some_argument' + 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: + +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 def guests(*array) array.each { |guest| puts guest } end -# If a method returns an array, you can use destructuring assignment -def foods - ['pancake', 'sandwich', 'quesadilla'] +# Destructuring + +# Ruby will automatically destrucure 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: + +ranked_competitors = ["John", "Sally", "Dingus", "Moe", "Marcy"] + +def best(first, second, third) + puts "Winners are #{first}, #{second}, and #{third}." end -breakfast, lunch, dinner = foods -breakfast #=> 'pancake' -dinner #=> 'quesadilla' + +best *ranked_competitors.first(3) #=> Winners are John, Sally, and Dingus. + +# 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." +end + +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 |