Ruby Diary 1

1.IRB parameter Configuration

~/.irbrc

IRB.conf[:PROMPT_MODE] = :SIMPLE #Simplify the irb prompt and disable some annoying auto-shrinking
IRB.conf[:AUTO_INDENT_MODE] = false

2. Notes:

#Single line

=begin

...... MultiRow

=end

3. String

String connection

>> "JK" + "JK" = "JKJK"

string interpolation

>> one = "foo" + "foo" >> "#{one} is one" and "Foo is one"

String printing

>> puts "jk" # comes with a newline after printing
Jk
=> nil
>> p "jk" #Print out the same as the original
"jk"
=> "jk"
>> print "jk" #Print does not wrap
Jk=> nil

Single double quote string

>> ‘jk\n#{one}‘ #Do not transfer characters and interpolate operations
=> "jk\\n\#{one}"
>> "jk\n#{one}" #output the escaped characters and interpolation operations
=> "jk\nfoo"

Object and Message Delivery

>> "jk".length
=> 2
>> "".empty?
=> true
>> "jk".nil?
=> false
>> "jk".include?("j")
=> true

When judging, you can cooperate with && (and) | | (OR)! (not) to operate

>> one = "foo" 
=> "foo"
>> two = ""
=> ""
>> if one.empty? && two.empty?
>> print "both empty"
>> elsif one.empty? || two.empty?
>> print "empty exist"
>> elsif !x.empty?
>> print "x is not empty"
>> end
empty exist=> nil

To_s can convert any object into a string

>> nil.to_s.empty?=> True

Unless judgment

>> two = "dasd"
=> "dasd"
>> print "ss" unless two.empty?
ss=> nil

Use!! Can be reversed twice to convert the object to a Boolean type

>> !!nil #nil object is boolean
=> false
>> !!0 #Others are true
=> true

Values and Ranges

Split method to split a string into a desired character array

>> "dasjkd das d dasd".split #default to remove spaces
=> ["dasjkd", "das", "d", "dasd"]
>> "fdjaskl,jfdskl,jfklasd".split(",") #Setup, split
=> ["fdjaskl", "jfdskl", "jfklasd"]

Index of the array

>> a=[12,34,45,67,89,8]=> [8]>> a[0]=> 12>> a[2]=> 45>> a[-4] #索引可. is negative = 45
>> a.fifth #Can look like this, but this is the effect rails adds
= 89
>> A.first
= 12
>> A.last
= 8

>> a=[12,34,45,67,89,08] #Note numbers cannot have 0 before, warning error Invalid decimal
SyntaxError: (IRB): 40: invalid octal digit
A=[12,34,45,67,89,08]
^

A series of methods for arrays

>> a.length
=> 6
>> a.include?(45)
=> true
>> a.sort # Arrange in ascending order (do not change the original array)
=> [8, 12, 34, 45, 67, 89]
>> a.reverse #order in turn
=> [8, 89, 67, 45, 34, 12]
>> a.shuffle #Random chaos => [45, 12, 8, 34, 67, 89]
>> a.sort! #Arrange in ascending order (change original array)
=> [8, 12, 34, 45, 67, 89]
>> a.push(4) #Add element (change original array)
=> [8, 12, 34, 45, 67, 89, 4]
>> a << 3 #Add elements (change the original array)
=> [8, 12, 34, 45, 67, 89, 4, 3]
>> a << "tu" << "re" #Add in series, and other types of elements can be added to the array
=> [8, 12, 34, 45, 67, 89, 4, 3, "tu", "re"]
>> a.join #merge strings
=> "8123445678943ture"
>> a.join(",") #add connector
=> "8,12,34,45,67,89,4,3,tu,re"

Range operations

>> (0...9). To_a # remove the last value, converting to an array
= = [0, 1, 2, 3, 4, 5, 6, 7, 8]
>> (0..9). To_a # Keep all to
= = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]>> a= (0..9). to_a
= = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
>> a[4: ( A.length)] #using the length method
= = [4, 5, 6, 7, 8, 9]
>> A[4..-2] #小技巧
= = [4, 5, 6, 7, 8]

Block

>> (1..9). Do |f|? > Print f*f>> end149162536496481
>> (1..9). Map {|i| I*i} #transform each element and return a map
= = [1, 4, 9, 16, 25, 36, 49, 64, 81]
>> (1..9). reduce {|i| I*i} #convert the entire array to a value return
= 1
>>%w{das das das} #%w transform element to string return
= = ["Das", "Das", "Das"]

Hashes and symbols

>> user = {} #initialize hash
== {}
>> user["one"] = "yz00"
= "Yz00"
>> user["both"] = "yz01"
= "yz01" >> user["one"] #Get hash
= "Yz00"
>> User
+ = {"One" = "yz00", "One" and "yz01"}>> user = {"One" = "yz00", "one" = "yz01"} # can also be assigned this way
+ = {"One" = "yz00", "One" and "yz01"} #Note that there is a space after the comma, the conventional

You can think of a symbol as a string without constraints, so it can be written in the following form

>> user = {: one = "yz00",: "yz01"} #Do not initialize == {:one=> "yz00",:two=> "yz01"}

Since the symbol is used more as a key, it is defined after 1.9

>> user = {one: "yz00", "One", "yz01"}
= = {:one=> "yz00",:two=> "yz01"}

Nested hashes

>> Users[:user] = user
= = {:one=> "yz00",:two=> "yz01"}
>> Users
= = {:user=>{:one=> "yz00",:two=> "Yz01"}}
>> Users[:user][:one]
= "Yz00"
>> print (1..5). to_a
[1, 2, 3, 4, 5]=> Nil
>> puts (1..5). to_a
1
2
3
4
5
= Nil
>> puts (1..5). To_a.inspect #inspect method outputs the literal form of the array, the output object is equivalent to the P method
[1, 2, 3, 4, 5]
= Nil
>> p (1..5). to_a
[1, 2, 3, 4, 5]
= = [1, 2, 3, 4, 5]

Ruby Diary 1