Class: NumRu::Misc::KeywordOpt

Inherits:
Object
  • Object
show all
Defined in:
lib/numru/misc/keywordopt.rb

Overview

Overview

A class to facilitate optional keyword arguments. More specifically, it helps the use of a Hash to mimic the keyword argument system. With this, you can set default values and description to each keyword argument.

Classes defined supplementarilly

class NumRu::Misc::HelpMessagingException < StandardError

This is for your convenience. See the usage example below.

Usage example

Suppose that you introduce keyword arguments “flag” and “number” to the method “hoge” in a class/module Foo. It can be done as follows:

require 'numru/misc'  # or, specifically, require 'numru/misc/keywordopt'
include NumRu

class Foo
  @@opt_hoge = Misc::KeywordOpt.new(
    ['flag',   false, 'whether or not ...'],
    ['number', 1,     'number of ...'],
    ['help',   false, 'show help message']
  )
  def hoge(regular_arg1, regular_arg2, options=nil)
    opt = @@opt_hoge.interpret(options)
    if opt['help']
      puts @@opt_hoge.help
      puts ' Current values='+opt.inspect
      raise Misc::HelpMessagingException, '** show help message and raise **'
    end
    # do what you want below 
    # (options are set in the Hash opt: opt['flag'] and opt['number'])
  end
end

Here, the options are defined in the class variable @@opt_hoge with option names, default values, and descriptions (for help messaging). One can use the method hoge as follows:

foo = Foo.new
...
x = ...
y = ...
...
foo.hoge( x, y, {'flag'=>true, 'number'=>10} )

Or equivalently,

foo.hoge( x, y, 'flag'=>true, 'number'=>10 )

because ‘{}’ can be omitted here.

Tails of options names can be shortened as long as unambiguous:

foo.hoge( x, y, 'fla'=>true, 'num'=>10 )

To show the help message, call

foo.hoge( x, y, 'help'=>true )

This will cause the following help message printed with the exception HelpMessagingException raised.

<< Description of options >>
 option name => default value   description:
  "flag" =>     false   whether or not ...
  "number" =>   1       number of ...
  "help" =>     false   show help message
Current values={"help"=>true, "number"=>1, "flag"=>false}
NumRu::Misc::HelpMessagingException: ** help messaging done **
       from (irb):78:in "hoge"
       from (irb):83

Do not affraid to write long descriptions. The help method

breaks lines nicely if they are long.

Direct Known Subclasses

KeywordOptAutoHelp

Instance Method Summary collapse

Constructor Details

#initialize(*args) ⇒ KeywordOpt

Constructor.

ARGUMENTS
* args : (case 1) arrays of two or three elements: [option name, 
  default value, description ], or [option name, default value]
  if you do not want to write descriptions. Option names and 
  descriptions must be String. (case 2) another KeywordOpt.
  Cases 1 and 2 can be mixed. 

  When case 2, a link to the other KeywordOpt is kept. Thus, change
  of values in it is reflected to the current one. However,
  the link is deleted if values are changed by <b>#set</b>.

RETURN VALUE
* a KeywordOpt object

EXAMPLE
* case 1
    opt = Misc::KeywordOpt.new(
      ['flag',   false, 'whether or not ...'],
      ['help',   false, 'show help message']
    )
* case 2
    opt = Misc::KeywordOpt.new( optA, optB )
* case 1 & 2
    opt = Misc::KeywordOpt.new(
      ['flag',   false, 'whether or not ...'],
      optA
    )



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# File 'lib/numru/misc/keywordopt.rb', line 122

def initialize(*args)
	# USAGE:
	#    KeywordOpt.new([key,val,description],[key,val,description],..)
	#    where key is a String, and description can be omitted.
	@val=Hash.new
	@description=Hash.new
	@keys = []
	args.each{ |x|
	  case x
	  when Array
	    unless (x[0]=='help') && @keys.include?(x[0])
 #^only 'help' can overwrap in the arguments
 @keys.push(x[0])
 @val[x[0]] = x[1]
 @description[x[0]] = ( (x.length>=3) ? x[2] : '' )
	    end
	  when KeywordOpt
	    x.keys.each{|k|
 unless k=='help' && @keys.include?(k)
   #^only 'help' can overwrap in the arguments
		@keys.push(k)
		@val[k] = x  #.val[k]
		@description[k] = x.description[k]
 end
	    }
	    def @val.[](k)
 val = super(k)
 val.is_a?(KeywordOpt) ? val[k] : val
	    end
	    def @val.dup
 out = Hash.new
 each{|k,val| out[k] = (val.is_a?(KeywordOpt) ? val[k] : val)}
 out
	    end
	  else
	    raise ArgumentError, "invalid argument: #{x.inspect}"
	  end
	}
	@keys_sort = @keys.sort
	if @keys_sort.length != @keys_sort.uniq.length
	  raise ArgumentError, "keys are not unique"
	end
end

Instance Method Details

#[](k) ⇒ Object

Returns a value associated with the key (exact matching unlike interpret)



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# File 'lib/numru/misc/keywordopt.rb', line 302

def [](k)
	v = @val[k]
	if v.is_a?(KeywordOpt)
	  v = v.val[k]
	end
	v
end

#help ⇒ Object

Returns a help message

RETURN VALUE
* a String describing the option names, default values, and descriptions



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# File 'lib/numru/misc/keywordopt.rb', line 294

def help
	 "  option name\tdefault value\t# description:\n" +
	 @keys.collect{|k| 
	   __line_feed("  #{k.inspect}\t#{@val[k].inspect}\t# #{@description[k]}", 66)
	 }.join("\n")
end

#interpret(hash) ⇒ Object

POSSIBLE EXCEPTION

* hash has a key that does not match any of the option names.
* hash has a key that is ambiguous



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# File 'lib/numru/misc/keywordopt.rb', line 185

def interpret(hash)
	return @val.dup if hash.nil?
	##
	len = @val.length
	im = 0
	out = @val.dup
	hash.keys.sort.each do |key|
	  rkey = /^#{key}/
	  loop do
	    if rkey =~ @keys_sort[im]
 if im<len-1 && rkey=~@keys_sort[im+1] &&
		 key != @keys_sort[im]   # not identical
		raise ArgumentError, "Ambiguous key specification '#{key}'." 
 end
 out[@keys_sort[im]]=hash[key]
 break
	    end
	    im += 1
	    if im==len
 raise ArgumentError, "'#{key}' does not match any of the keys."
	    end
	  end
	end
	out
end

#keys ⇒ Object

Returns the keys.



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# File 'lib/numru/misc/keywordopt.rb', line 311

def keys
	@keys.dup
end

#select_existent(hash_or_keys) ⇒ Object

Copies hash_or_keys, exclude ones that are not included in the option

(by comparing keys), and returns it. I.e. select only the ones 
exsitent. 

NOTE: ambiguity is not checked, so the resultant value is not 
necessarily accepted by <b>#interpret</b>.

ARGUMENTS
* hash_or_keys (Hash or Array)

RETURN VALUE
* a Hash or Array depending on the class of the argument hash_or_keys



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# File 'lib/numru/misc/keywordopt.rb', line 223

def select_existent(hash_or_keys)
	hash_or_keys = hash_or_keys.dup         # not to alter the original
	len = @val.length
	im = 0
	kys = ( Array === hash_or_keys ? hash_or_keys : hash_or_keys.keys )
	kys.sort.each do |key|
	  rkey = /^#{key}/
	  loop do
	    break if rkey =~ @keys_sort[im]
	    im += 1
	    if im==len
 hash_or_keys.delete(key)
 im = 0           # rewind
        break
	    end
	  end
	end
	hash_or_keys
end

#set(hash) ⇒ Object

Similar to #interpret but changes internal values.

ARGUMENTS
* hash (Hash) : see <b>#interpret</b>. (Here, nil is not permitted though)

RETURN VALUE
* a Hash containing the values replaced (the ones before calling this 
  method)

POSSIBLE EXCEPTION
* the argument is not a Hash
* others are same as in <b>#interpret</b>

Raises:

  • (ArgumentError) 


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# File 'lib/numru/misc/keywordopt.rb', line 255

def set(hash)
	raise ArgumentError, "not a hash" if !hash.is_a?(Hash)
	##
	replaced = Hash.new
	len = @val.length
	im = 0
	hash.keys.sort.each do |key|
	  rkey = /^#{key}/
	  loop do
	    if rkey =~ @keys_sort[im]
 if im<len-1 && rkey=~@keys_sort[im+1]
		raise "Ambiguous key specification '#{key}'." 
 end
 replaced[@keys_sort[im]] = @val[@keys_sort[im]]
 @val[@keys_sort[im]]=hash[key]
 break
	    end
	    im += 1
	    raise "'#{key}' does not match any of the keys." if im==len
	  end
	end
	replaced
end