ruby data type String

1. String creation

1. Single quotes are included, escape characters and embedded expressions #{} (interpolation characters) are not supported
   

   str  = 'hello world!'

    

2. double quotes contain
   

   str = "hello world!"

    

3. Use %, %Q, %q (followed by <>, {}, ||, [], etc.)
   

   str = %|\there is test!|
   puts str     #=> here is test!  str = %Q|\there is test!| puts str #=> here is test!  str = %q|\there is test!| puts str #=> \there is test!

   %Q is equivalent to " " to create a string, %q is equivalent to ' ' to create a string
   Usage scenario: you need to construct a very long string, and it contains a lot of single quotes and double quotes
   
   

4. HERE document representation method (especially suitable for representing large paragraphs of text with multiple lines)
   

   str = <<HERE
   This is a here document!
   You can enter " multi-line content " in this block HERE 
   
   here HERE must be written at the beginning of the line, otherwise it will not be considered as a closing identifier
   

   str = <<-HERE 
   This is a here document! 
   You can enter " multiline content" in this block 
    HERE

   <<- closing identifier, spaces and tabs before the closing identifier will be ignored; so that it does not need to be written at the beginning of the line
   

   Support for escape characters and embedded strings

 

2. Basic operation

• [] string element reference
  

  str = 'Element reference test' puts str[1] #=> l　　 puts str[0, 7] #=> Element puts str[0..3] #=> Elem puts str[-4, 4] #=> test puts str[/n([a-z])/] #=> nt puts str[/n([a-z])/, 1] #=> t puts str['ref'] #=> ref puts str['hello'] #=> nil

  The above shows 6 methods of str[int], str[int, int], str[range], str[regexp], str[regexp, int], str[string]

• []= string element assignment
  

  str = 'Element reference test' str[0] = 'e' puts str #=> element reference test  str[0, 7] = 'ABCD' puts str #=> ABCD reference test

   

• *, +, <<
  

  str = ' test '  puts str*3 # => testtesttest puts str + ' ! ' # => test! puts str # => test puts str << ' ! ' # => test! puts str # => test! < < will change the original object

   

3. Common methods

str.length, str.size #=> returns the length of the string
str.concat(obj)　　#=> Append string, similar to <<
str.capitalize　　#=> Capitalize the first letter of the string, and lowercase the rest
str.delete(string)　　#=> Delete the string and return the deleted part 
str.each_byte{ |int| ...}　　#=> Iterate over each byte in the string
str.each_line{ |line| ...}　　#=> Iterate over each line of the string
str.strip　　#=> Remove invisible characters (spaces) from the end of the string 
str.chop　　#=>Remove the last character in str
 str.chomp　　#=>Remove the record separator from the end of the string 
str.downcase　　# => string converted to lowercase
str.upcase　　#=> convert string to uppercase
str.include?(obj)　　#=> Return true if string is included, otherwise return false
str.index(string)　　#=> Returns the position where the string string appears for the first time in the string; the rindex method starts to retrieve from the back
str.reverse　　#=> reverse the string
str.split(pattern, <limit> )　　#=> Split the string str into several substrings based on the delimiter pattern and return it as an array
str.scan(pattern)　　#=> Search for all matching patterns in str 
str.sub( pattern, replacement )　　#=>Replace the first string matching pattern with replacement
 str.gsub(pattern, replacement)　　#=> Replace All strings matching pattern are replacement
 str.count(string, ...) #=> Count the number of occurrences of string