ruby on rails 继续ing

ruby API http://ruby-doc.org/core-1.9.3/

rails API http://api.rubyonrails.org/v3.2.0/classes/ActionView/Helpers/AssetTagHelper/StylesheetTagHelpers.html#method-i-stylesheet_link_tag

 0 (and everything other than nil and false itself) is true

>>  "foo bar  baz".split     # Split a string into a three-element array
=> ["foo", "bar", "baz"]   将字符串转为array

>> "fooxbarxbazx".split('x')
=> ["foo", "bar", "baz"]

>> a = [42, 8, 17]
=> [42, 8, 17]
>> a[0]               # Ruby uses square brackets for array access.
=> 42

>> a                  # Just a reminder of what 'a' is
=> [42, 8, 17]
>> a.first

42

感叹号的作用

>> a
=> [42, 8, 17]
>> a.sort
=> [8, 17, 42]
>> a.reverse
=> [17, 8, 42]
>> a.shuffle
=> [17, 42, 8]
>> a
=> [42, 8, 17]

>> a
=> [42, 8, 17]
>> a.sort!
=> [8, 17, 42]
>> a
=> [8, 17, 42]

>> a.push(6)                  # Pushing 6 onto an array
=> [42, 8, 17, 6]
>> a << 7                     # Pushing 7 onto an array
=> [42, 8, 17, 6, 7]
>> a << "foo" << "bar"        # Chaining array pushes
=> [42, 8, 17, 6, 7, "foo", "bar"]

join

>> a
=> [42, 8, 17, 7, "foo", "bar"]
>> a.join                       # Join on nothing
=> "428177foobar"
>> a.join(', ')                 # Join on comma-space
=> "42, 8, 17, 7, foo, bar"

>> a = %w[foo bar baz quux]         # Use %w to make a string array.
=> ["foo", "bar", "baz", "quux"]
>> a[0..2]
=> ["foo", "bar", "baz"]

>> (0..9).to_a                                    # Use parentheses to call to_a on the range
=> [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]

>> ('a'..'e').to_a
=> ["a", "b", "c", "d", "e"]

>> (1..5).each { |i| puts 2 * i }

>> (1..5).each do |i|
?>   puts 2 * i
>> end

(1..5).map { |i| i**2 }  

=> [1, 4, 9, 16, 25]

the map method returns the result of applying the given block to each element in the array or range.

hash用法

>> user = {}                          # {} is an empty hash.
=> {}
>> user["first_name"] = "Michael"     # Key "first_name", value "Michael"
=> "Michael"
>> user["last_name"] = "Hartl"        # Key "last_name", value "Hartl"
=> "Hartl"
>> user["first_name"]                 # Element access is like arrays.
=> "Michael"
>> user                               # A literal representation of the hash
=> {"last_name"=>"Hartl", "first_name"=>"Michael"}

>> user = { "first_name" => "Michael", "last_name" => "Hartl" }

symbo用法

>> user = { :name => "Michael Hartl", :email => "michael@example.com" }
=> {:name=>"Michael Hartl", :email=>"michael@example.com"}

{ name: "Michael Hartl", email: "michael@example.com" }   //上面这两个是一样的

>> user[:name]              # Access the value corresponding to :name.
=> "Michael Hartl"
>> user[:password]          # Access the value of an undefined key.
=> nil

嵌套的hash symbol

> params = {}        # Define a hash called 'params' (short for 'parameters').
=> {}
>> params[:user] = { name: "Michael Hartl", email: "mhartl@example.com" }
=> {:name=>"Michael Hartl", :email=>"mhartl@example.com"}
>> params
=> {:user=>{:name=>"Michael Hartl", :email=>"mhartl@example.com"}}
>>  params[:user][:email]
=> "mhartl@example.com"

>> flash = { success: "It worked!", error: "It failed." }
=> {:success=>"It worked!", :error=>"It failed."}

inspect用法

puts "It worked!", "It worked!".inspect
It worked!
"It worked!"

>> a = Array.new([1, 3, 2])

=> [1, 3, 2]           类实例化

自己修改String基类

>> class String
>>   # Returns true if the string is its own reverse.
>>   def palindrome?
>>     self == self.reverse
>>   end
>> end
=> nil
>> "deified".palindrome?
=> true

class User
  attr_accessor :name, :email
 def initialize(attributes = {})
    @name  = attributes[:name]
    @email = attributes[:email]
  end
  def formatted_email
    "#{@name} <#{@email}>"
  end
end

   In Rails, the principal importance of instance variables is that they are automatically available in the views, but in general they are used for variables that need to be available throughout a Ruby class.When we execute User.new. This particular initialize takes one argument, attributes。

如何引入一个类

>> require './example_user'     # This is how you load the example_user code.

=> ["User"]
>> example = User.new

    user = User.new(name: "Michael Hartl", email: "mhartl@example.com")