Ruby on Rails Tutorial fourth the other data types of ruby behind Rails

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1. Arrays and Ranges

2, Block

Convention: Use curly braces when there is only a single line of code in the block, when the block is a long line of code, or when there are many rows using do. End form. For example:

>> (1..5). Each{|i| putsi} (1..5). Each do |i|puts*I puts'-'End>> 3.times{puts"Betelgeuse"}>> (1..5). map{|i| i**2}>>%w[a b c].map{|char|Char.upcase}>>%w[a B c].map{|char|Char.downcase}>>%w[a B C].map (&:d owncase)>> ('a'..'Z'). To_a.shuffle[0..7].join#generate a random two-level domain name

3. Hashes and symbols

A hash is essentially an array, and its index is not limited to numbers. The index of the hash can use any object. A hash is represented by a pair of curly braces that contains some key-value pairs. The biggest difference between hashes and arrays is that hash elements do not have a specific order. Hash the value of a key that is not defined is nil

>> user={}#{} is an empty hash>> user["first_name"]="Amy">> user["last_name"]="Sun">> user["first_name"]="Amy">>User= = {"first_name"="Amy","last_name"="Sun"}>> user["e-Mail"]=Nil>> user={"first_name"="Amy","last_name"="Sun" }=>{"first_name"="Amy","last_name"="Sun"}

symbol : A unique data type in Ruby, a string with no constraints

>> user={:name=>"Amysun",:email=>"12***[email protected]**.com" }= {:name=>"Amysun",:email=>"12***[email protected]**.com"}>>User[:name]="Amysun">>user[:p Assword]=Nil>> h1={:name=>"Amysun",:email=>"12***[email protected]**.com" }= {:name=>"Amysun",:email=>"12***[email protected]**.com"}>> h1={Name:"Amysun", Email:"12***[email protected]**.com"}#:name=> and name: the same, so {:name=> "Amysun"} and {name: "Amysun"} are equivalent, but only: name represents the symbol= {:name=>"Amysun",:email=>"12***[email protected]**.com"}>> h1==H2= True

Nested hashes

>> params={}= {}>> params[:user]={Name:"Amysun", Email:"12***[email protected]**.com" }= {:name=>"Amysun",:email=>"12***[email protected]**.com"}>>params= {:user=>{:name=>"Amysun",:email=>"12***[email protected]**.com"}}>>Params[:user][:email]= 12***[email protected]**.com

Each method of hash

>> user={Success:"It worked!", Danger:"It failed." }= {:success=>"It worked!",:d anger=>"It failed."}user.each Do|key,value|puts"Key #{key.inspect} has value #{value.inspect}"End#Results#key:success has value "It worked!"#key:failed has value "It failed."

Where the inspect method returns the string literal representation of the called object, for example:

>> puts (1..5) to_a.inspect[1,2,3,4,5]>> puts:name,:name.inspectname:name " It worked! ","It worked! " . Inspectit worked! " It worked! ">> p:name  # equivalent to ' Puts:name.inspect ': Name

4. Introduction of CSS Instructions

' Application ', media:'all','data-trubolinks-track'=>true% >

Description: When calling a function, if the hash is the last argument, you can omit the curly brace, because Data-trubolinks-track has hyphens, so it cannot be written as Data-trubolinks-track: The true style generates HTML source code as follows:

<link data-trubolinks-track="true" href="/assets/application.css " media="alll" rel="stylesheet "/>

Ruby on Rails Tutorial fourth the other data types of ruby behind Rails

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