ruby学习笔记（3）- 新手入门

这里是一个Ruby开发的快速参考指南:

Ruby是什么 ?

Ruby是一种纯粹的面向对象编程语言。它由日本松本幸创建于1993年。 Ruby是一种通用的解释编程语言如Perl和Python.

IRb是什么 ?

交互式Ruby（IRB）为实验提供了一个shell。内置IRB shell，你可以立即一行行查看表达式的结果。
该工具自带Ruby安装，所以你必须做一些额外的IRB工作无关。只需键入在命令提示符IRB和交互式Ruby会话将启动.

Ruby语法:

• Ruby代码一般忽略空白字符，如空格和制表符，除非当他们出现在字符串.

• Ruby的解释分号作为语句的结尾换行符。但是，如果ruby遇到运算符，如+， - ，或在一行的末尾的反斜杠，他们的声明中表示延续.

• 标识符名称的变量，常量和方法。 Ruby的标识符是大小写敏感。这意味着Ram和RAM是两个不同的标识符在Ruby.

• Ruby注释开始与pound/sharp (#)字符，去行结束(EOL).

保留字:

以下列表显示了在Ruby中的保留字。然而，这些保留字不应该被用来作为程序中的常量或变量名，被用来作为方法名称.

BEGIN	do	next	then
END	else	nill	true
alias	elsif	not	undef
and	end	or	unless
begin	ensure	redo	until
break	false	rescue	when
case	for	retry	while
class	if	return	while
def	in	self	__FILE__
defined?	module	super	__LINE__

Ruby定界符文本:

下面是不同的例子:

#!/usr/bin/ruby -w
print <<EOF
    This is the first way of creating
    her document ie. multiple line string.
EOF
print <<"EOF";                # same as above by www.yiibai.com
    This is the second way of creating
    her document ie. multiple line string.
EOF
print <<`EOC`                 # execute commands
	echo hi there
	echo lo there
EOC
print <<"foo", <<"bar"  # you can stack them
	I said foo.
foo
	I said bar.
bar

Ruby数据类型:

基本类型是数字，字符串，范围，数组和哈希值，.

Ruby中的整数:

123                  # Fixnum decimal
1_6889               # Fixnum decimal with underline
-5000                # Negative Fixnum
0377                 # octal
0xee                 # hexadecimal
0b1011011            # binary
?b                   # character code for 'b'
?\n                  # code for a newline (0x0a)
12345678901234567890 # Bignum

Ruby中的浮点数:

1023.4               # floating point value
1.0e6                # scientific notation
4E20                 # dot not required
4e+20                # sign before exponential

字符串常量:

Ruby字符串简单的8位字节的序列，他们是String类的对象.

• 'VariableName': No interpolation will be done
• "#{VariableName} and Backslashes \n:" Interpolation will be done
• %q(VariableName): No interpolation will be done
• %Q(VariableName and Backslashes \n): Interpolation will be done
• %(VariableName and Backslashes \n): Interpolation will be done
• `echo command interpretation with interpolation and backslashes`
• %x(echo command interpretation with interpolation and backslashes)

反斜线符号:

以下是由Ruby支持反斜线符号列表:

Notation	Character represented
\n	Newline (0x0a)
\r	Carriage return (0x0d)
\f	Formfeed (0x0c)
\b	Backspace (0x08)
\a	Bell (0x07)
\e	Escape (0x1b)
\s	Space (0x20)
\nnn	Octal notation (n being 0-7)
\xnn	Hexadecimal notation (n being 0-9, a-f, or A-F)
\cx, \C-x	Control-x
\M-x	Meta-x (c | 0x80)
\M-\C-x	Meta-Control-x
\x	Character x

Ruby数组:

创建对象引用方括号内放置一个逗号分隔的一系列Ruby数组的文字。一个被忽略尾随逗号.

例子:

#!/usr/bin/ruby
ary = [  "Ali", 10, 3.14, "This is a string", "last element", ]
ary.each do |i|
   puts i
end

这将产生以下结果:

Ali
10
3.14
This is a string
last element

Ruby 哈希:

文字的Ruby创建哈希放在括号之间的键/值对的列表，用逗号或=>之间的键和值序列。一个被忽略尾随逗号.

例子:

#!/usr/bin/ruby
hsh = colors = { "red" => 0xf00, "green" => 0x0f0 }
hsh.each do |key, value|
   print key, " is ", value, "\n"
end

这将产生以下结果:

green is 240
red is 3840

Ruby范围:

一个范围代表一个开始和结束值interval.a集。范围可使用.. E和...é文字，或使用Range.new构建.

范围使用......包含从开始运行到结束。那些使用...排除最终价值。作为一个迭代器使用时，范围返回序列中的每个值.

一个范围（1 .. 5）意味着它包括1，2，3，4，5个值和范围（1 ... 5）意味着它包括2，3，4值.

例子:

#!/usr/bin/ruby
(10..15).each do |n|
   print n, ' '
end

这将产生以下结果:

10 11 12 13 14 15

变量类型:

• $global_variable（全局变量)

• @@class_variable(类变量)

• @instance_variable

• [OtherClass::]CONSTANT

• local_variable

Ruby的伪变量:

他们是特殊的变量，局部变量的外观，但像常数。你不能指定任何这些变量的值.

• self: The receiver object of the current method.

• true: Value representing true.

• false: Value representing false.

• nil: Value representing undefined.

• __FILE__: The name of the current source file.

• __LINE__: The current line number in the source file.

Ruby的预定义变量:

下表列出了所有Ruby的预定义变量.

Variable Name	Description
$!	The last exception object raised. The exception object can also be accessed using => in rescue clause.
$@	The stack backtrace for the last exception raised. The stack backtrace information can retrieved by Exception#backtrace method of the last exception.
$/	The input record separator (newline by default). gets, readline,etc., take their input record separator as optional argument.
$\	The output record separator (nil by default).
$,	The output separator between the arguments to print and Array#join (nil by default). You can specify separator explicitly to Array#join.
$;	The default separator for split (nil by default). You can specify separator explicitly for String#split.
$.	The number of the last line read from the current input file. Equivalent to ARGF.lineno.
$<	Synonym for ARGF.
$>	Synonym for $defout.
$0	The name of the current Ruby program being executed.
$$	The process pid of the current Ruby program being executed.
$?	The exit status of the last process terminated.
$:	Synonym for $LOAD_PATH.
$DEBUG	True if the -d or --debug command-line option is specified.
$defout	The destination output for print and printf ($stdout by default).
$F	The variable that receives the output from split when -a is specified. This variable is set if the -a command-line option is specified along with the -p or -n option.
$FILENAME	The name of the file currently being read from ARGF. Equivalent to ARGF.filename.
$LOAD_PATH	An array holding the directories to be searched when loading files with the load and require methods.
$SAFE	The security level 0 --> No checks are performed on externally supplied (tainted) data. (default) 1 --> Potentially dangerous operations using tainted data are forbidden. 2 --> Potentially dangerous operations on processes and files are forbidden. 3 --> All newly created objects are considered tainted. 4 --> Modification of global data is forbidden.
$stdin	Standard input (STDIN by default).
$stdout	Standard output (STDOUT by default).
$stderr	Standard error (STDERR by default).
$VERBOSE	True if the -v, -w, or --verbose command-line option is specified.
$- x	The value of interpreter option -x (x=0, a, d, F, i, K, l, p, v). These options are listed below
$-0	The value of interpreter option -x and alias of $/.
$-a	The value of interpreter option -x and true if option -a is set. Read-only.
$-d	The value of interpreter option -x and alias of $DEBUG
$-F	The value of interpreter option -x and alias of $;.
$-i	The value of interpreter option -x and in in-place-edit mode, holds the extension, otherwise nil. Can enable or disable in-place-edit mode.
$-I	The value of interpreter option -x and alias of $:.
$-l	The value of interpreter option -x and true if option -lis set. Read-only.
$-p	The value of interpreter option -x and true if option -pis set. Read-only.
$_	The local variable, last string read by gets or readline in the current scope.
$~	The local variable, MatchData relating to the last match. Regex#match method returns the last match information.
$ n ($1, $2, $3...)	The string matched in the nth group of the last pattern match. Equivalent to m[n], where m is a MatchData object.
$&	The string matched in the last pattern match. Equivalent to m[0], where m is a MatchData object.
$`	The string preceding the match in the last pattern match. Equivalent to m.pre_match, where m is a MatchData object.
$'	The string following the match in the last pattern match. Equivalent to m.post_match, where m is a MatchData object.
$+	The string corresponding to the last successfully matched group in the last pattern match.
$+	The string corresponding to the last successfully matched group in the last pattern match.

Ruby预定义的常量:

下表列出了所有Ruby的预定义常量.

注: TRUE, FALSE 和 NIL 无是向后兼容的。这是最好用 true, false, and nil.

Constant Name	Description
TRUE	Synonym for true.
FALSE	Synonym for false.
NIL	Synonym for nil.
ARGF	An object providing access to virtual concatenation of files passed as command-line arguments or standard input if there are no command-line arguments. A synonym for $<.
ARGV	An array containing the command-line arguments passed to the program. A synonym for $*.
DATA	An input stream for reading the lines of code following the __END__ directive. Not defined if __END__ isn't present in code.
ENV	A hash-like object containing the program's environment variables. ENV can be handled as a hash.
RUBY_PLATFORM	A string indicating the platform of the Ruby interpreter.
RUBY_RELEASE_DATE	A string indicating the release date of the Ruby interpreter
RUBY_VERSION	A string indicating the version of the Ruby interpreter.
STDERR	Standard error output stream. Default value of $stderr.
STDIN	Standard input stream. Default value of $stdin.
STDOUT	Standard output stream. Default value of $stdout.
TOPLEVEL_BINDING	A Binding object at Ruby's top level.

正则表达式:

语法:

/pattern/
/pattern/im    # option can be specified
%r!/usr/local! # general delimited regular expression

修饰符:

Modifier	Description
i	Ignore case when matching text.
o	Perform #{} interpolations only once, the first time the regexp literal is evaluated.
x	Ignores whitespace and allows comments in regular expressions
m	Matches multiple lines, recognizing newlines as normal characters
u,e,s,n	Interpret the regexp as Unicode (UTF-8), EUC, SJIS, or ASCII. If none of these modifiers is specified, the regular expression is assumed to use the source encoding.

各种模式:

Pattern	Description
^	Matches beginning of line.
$	Matches end of line.
.	Matches any single character except newline. Using m option allows it to match newline as well.
[...]	Matches any single character in brackets.
[^...]	Matches any single character not in brackets
re*	Matches 0 or more occurrences of preceding expression.
re+	Matches 0 or 1 occurrence of preceding expression.
re{ n}	Matches exactly n number of occurrences of preceding expression.
re{ n,}	Matches n or more occurrences of preceding expression.
re{ n, m}	Matches at least n and at most m occurrences of preceding expression.
a| b	Matches either a or b.
(re)	Groups regular expressions and remembers matched text.
(?imx)	Temporarily toggles on i, m, or x options within a regular expression. If in parentheses, only that area is affected.
(?-imx)	Temporarily toggles off i, m, or x options within a regular expression. If in parentheses, only that area is affected.
(?: re)	Groups regular expressions without remembering matched text.
(?imx: re)	Temporarily toggles on i, m, or x options within parentheses.
(?-imx: re)	Temporarily toggles off i, m, or x options within parentheses.
(?#...)	Comment.
(?= re)	Specifies position using a pattern. Doesn't have a range.
(?! re)	Specifies position using pattern negation. Doesn't have a range.
(?> re)	Matches independent pattern without backtracking.
\w	Matches word characters.
\W	Matches nonword characters.
\s	Matches whitespace. Equivalent to [\t\n\r\f].
\S	Matches nonwhitespace.
\d	Matches digits. Equivalent to [0-9].
\D	Matches nondigits.
\A	Matches beginning of string.
\Z	Matches end of string. If a newline exists, it matches just before newline.
\z	Matches end of string.
\G	Matches point where last match finished.
\b	Matches word boundaries when outside brackets. Matches backspace (0x08) when inside brackets.
\B	Matches nonword boundaries.
\n, \t, etc.	Matches newlines, carriage returns, tabs, etc.
\1...\9	Matches nth grouped subexpression.
\10	Matches nth grouped subexpression if it matched already. Otherwise refers to the octal representation of a character code.

文件I/O:

常见的方法包括：:

• File.join(p1, p2, ... pN) => "p1/p2/.../pN"  独立于平台路径

• File.new(path, modestring="r") => file

• File.new(path, modenum [, permnum]) => file

• File.open(fileName, aModeString="r") {|file| block} -> nil

• File.open(fileName [, aModeNum [, aPermNum ]]) {|file| block} -> nil

• IO.foreach(path, sepstring=$/) {|line| block}

• IO.readlines(path) => array

这里是一个不同的模式打开一个文件列表:

Modes	Description
r	Read-only mode. The file pointer is placed at the beginning of the file. This is the default mode.
r+	Read-write mode. The file pointer will be at the beginning of the file.
w	Write-only mode. Overwrites the file if the file exists. If the file does not exist, creates a new file for writing.
w+	Read-write mode. Overwrites the existing file if the file exists. If the file does not exist, creates a new file for reading and writing.
a	Write-only mode. The file pointer is at the end of the file if the file exists. That is, the file is in the append mode. If the file does not exist, it creates a new file for writing.
a+	Read and write mode. The file pointer is at the end of the file if the file exists. The file opens in the append mode. If the file does not exist, it creates a new file for reading and writing.

运算符和优先级:

从上到下:

:: .
[]
**
-(unary) +(unary) ! ~
*  /  %
+  -
<<  >>
&
|  ^
>  >=  <  <=
<=> == === != =~ !~
&&
||
.. ...
=(+=, -=...)
not
and or

以上都只是除了这些方法:

=, ::, ., .., ..., !, not, &&, and, ||, or, !=, !~

此外，赋值运算符（+=等）用户可定义.

控制表达式:

S.N.	Control Expression
1	if bool-expr [then] body elsif bool-expr [then] body else body end
2	unless bool-expr [then] body else body end
3	expr if bool-expr
4	expr unless bool-expr
5	case target-expr when comparison [, comparison]... [then] body when comparison [, comparison]... [then] body ... [else body] end
6	loop do body end
7	while bool-expr [do] body end
8	until bool-expr [do] body end
9	begin body end while bool-expr
10	begin body end until bool-expr
11	for name[, name]... in expr [do] body end
12	expr.each do | name[, name]... | body end
13	expr while bool-expr
14	expr until bool-expr

• break 立即终止循环.
• redo 立即重复w/w重新运行条件.
• next 通过循环开始下一次迭代.
• retry 重启循环，重新运行条件.

定义一个类:

类名w/ 资本开始字符.

class Identifier [< superclass ]
  expr..
end

Singleton类，一个实例添加方法

class << obj
  expr..
end

定义模块:

以下是Ruby中一般来定义一个模块的语法

module Identifier
  expr..
end

定义方法:

以下是Ruby中一般来定义一个方法的语法

def method_name(arg_list, *list_expr, &block_expr)
  expr..
end
# singleton method
def expr.identifier(arg_list, *list_expr, &block_expr)
  expr..
end

• All items of the arg list, including parens, are optional.
• Arguments may have default values (name=expr).
• Method_name may be operators (see above).
• The method definitions can not be nested.
• Methods may override following operators:
  • .., |, ^, &, <=>, ==, ===, =~,
  • >, >=, <, <=,
  • +, -, *, /, %, **, <<, >>,
  • ~, +@, -@, [], []= (2 args)

访问限制:

• public - 完全访问.

• protected - 只能通过访问类和直接后裔的实例。即使是通过一个关系。 （见下文）

• private - 只能通过类的实例访问（必须在调用nekkid没有“self”或其他）.

例子:

class A
  protected
  def protected_method
    # nothing
  end
end
class B < A
  public
  def test_protected
    myA = A.new
    myA.protected_method
  end
end
b = B.new.test_protected

抛出和挽救异常:

以下是语法:

raise ExceptionClass[, "message"]
begin
  expr..
[rescue [error_type [=> var],..]
  expr..]..
[else
  expr..]
[ensure
  expr..]
end

捕捉和抛出异常:

• catch (:label) do ... end
• throw :label jumps back to matching catch and terminates the block.
• + can be external to catch, but has to be reached via calling scope.
• + Hardly ever needed.

异常类:

以下是Exception类的类层次结构:

• Exception
  • NoMemoryError
  • ScriptError
    • LoadError
    • NotImplementedError
    • SyntaxError
  • SignalException
    • Interrupt
  • StandardError (default for rescue)
    • ArgumentError
    • IOError
      • EOFError
    • IndexError
    • LocalJumpError
    • NameError
      • NoMethodError
    • RangeError
      • FloatDomainError
    • RegexpError
    • RuntimeError (default for raise)
    • SecurityError
    • SystemCallError
      • Errno::*
    • SystemStackError
    • ThreadError
    • TypeError
    • ZeroDivisionError
  • SystemExit
  • fatal

Ruby命令行选项:

$ ruby [ options ] [.] [ programfile ] [ arguments ... ]

解释器可以调用任何下列选项来控制环境和行为的解释.

Option	Description
-a	Used with -n or -p to split each line. Check -n and -p options.
-c	Checks syntax only, without executing program.
-C dir	Changes directory before executing (equivalent to -X).
-d	Enables debug mode (equivalent to -debug).
-F pat	Specifies pat as the default separator pattern ($;) used by split.
-e prog	Specifies prog as the program from the command line. Specify multiple -e options for multiline programs.
-h	Displays an overview of command-line options.
-i [ ext]	Overwrites the file contents with program output. The original file is saved with the extension ext. If ext isn't specified, the original file is deleted.
-I dir	Adds dir as the directory for loading libraries.
-K [ kcode]	Specifies the multibyte character set code (e or E for EUC (extended Unix code); s or S for SJIS (Shift-JIS); u or U for UTF-8; and a, A, n, or N for ASCII).
-l	Enables automatic line-end processing. Chops a newline from input lines and appends a newline to output lines.
-n	Places code within an input loop (as in while gets; ... end).
-0[ octal]	Sets default record separator ($/) as an octal. Defaults to \0 if octal not specified.
-p	Places code within an input loop. Writes $_ for each iteration.
-r lib	Uses require to load lib as a library before executing.
-s	Interprets any arguments between the program name and filename arguments fitting the pattern -xxx as a switch and defines the corresponding variable.
-T [level]	Sets the level for tainting checks (1 if level not specified).
-v	Displays version and enables verbose mode
-w	Enables verbose mode. If programfile not specified, reads from STDIN.
-x [dir]	Strips text before #!ruby line. Changes directory to dir before executing ifdir is specified.
-X dir	Changes directory before executing (equivalent to -C).
-y	Enables parser debug mode.
--copyright	Displays copyright notice.
--debug	Enables debug mode (equivalent to -d).
--help	Displays an overview of command-line options (equivalent to -h).
--version	Displays version.
--verbose	Enables verbose mode (equivalent to -v). Sets $VERBOSE to true
--yydebug	Enables parser debug mode (equivalent to -y).

Ruby环境变量:

Ruby解释器使用以下环境变量来控制其行为。在env对象包含了所有当前的环境变量设置列表.

Variable	Description
DLN_LIBRARY_PATH	Search path for dynamically loaded modules.
HOME	Directory moved to when no argument is passed to Dir::chdir. Also used by File::expand_path to expand "~".
LOGDIR	Directory moved to when no arguments are passed to Dir::chdir and environment variable HOME isn't set.
PATH	Search path for executing subprocesses and searching for Ruby programs with the -S option. Separate each path with a colon (semicolon in DOS and Windows).
RUBYLIB	Search path for libraries. Separate each path with a colon (semicolon in DOS and Windows).
RUBYLIB_PREFIX	Used to modify the RUBYLIB search path by replacing prefix of library path1 with path2 using the format path1;path2 or path1path2.
RUBYOPT	Command-line options passed to Ruby interpreter. Ignored in taint mode (Where $SAFE is greater than 0).
RUBYPATH	With -S option, search path for Ruby programs. Takes precedence over PATH. Ignored in taint mode (where $SAFE is greater than 0).
RUBYSHELL	Specifies shell for spawned processes. If not set, SHELL or COMSPEC are checked.