U:RDoc::TopLevel[	iI"syntax/methods.rdoc:EFcRDoc::Parser::Simpleo:RDoc::Markup::Document:@parts[
»S:RDoc::Markup::Heading:
leveli:	textI"Methods;To:RDoc::Markup::BlankLineo:RDoc::Markup::Paragraph;[I"SMethods implement the functionality of your program.  Here is a simple method ;TI"definition:;T@
o:RDoc::Markup::Verbatim;[I"def one_plus_one
;TI"
  1 + 1
;TI"	end
;T:@format0o;
;[I"SA method definition consists of the +def+ keyword, a method name, the body of ;TI"Tthe method, +return+ value and the +end+ keyword.  When called the method will ;TI">execute the body of the method.  This method returns +2+.;T@
o;
;[I"TThis section only covers defining methods.  See also the {syntax documentation ;TI"?on calling methods}[rdoc-ref:syntax/calling_methods.rdoc].;T@
S;	;
i;I"Method Names;T@
o;
;[	I"TMethod names may be one of the operators or must start a letter or a character ;TI"Pwith the eight bit set. It may contain letters, numbers, an <code>_</code> ;TI"T(underscore or low line) or a character with the eight bit set. The convention ;TI"His to use underscores to separate words in a multiword method name:;T@
o;;[I"def method_name
;TI"0  puts "use underscores to separate words"
;TI"	end
;T;0o;
;[
I"RRuby programs must be written in a US-ASCII-compatible character set such as ;TI"NUTF-8, ISO-8859-1 etc. In such character sets if the eight bit is set it ;TI"Uindicates an extended character. Ruby allows method names and other identifiers ;TI"Sto contain such characters. Ruby programs cannot contain some characters like ;TI""ASCII NUL (<code>\x00<code>).;T@
o;
;[I":The following are the examples of valid ruby methods:;T@
o;;[I"def hello
;TI"  "hello"
;TI"	end
;TI"
;TI"def こんにちは
;TI"&  puts "means hello in Japanese"
;TI"	end
;T;0o;
;[I"PTypically method names are US-ASCII compatible since the keys to type them ;TI"exist on all keyboards.;T@
o;
;[I"NMethod names may end with a <code>!</code> (bang or exclamation mark), a ;TI"B<code>?</code> (question mark) or <code>=</code> equals sign.;T@
o;
;[I"OThe bang methods(<code>!</code> at the end of method name) are called and ;TI"Sexecuted just like any other method. However, by convention, a method with an ;TI"Qexclamation point or bang is considered dangerous. In ruby core library the ;TI"Sdangerous method implies that when a method ends with a bang(<code>!</code>), ;TI"Pit indicates that unlike its non-bang equivalent, permanently modifies its ;TI"Ereceiver. Almost always, Ruby core library will have a non-bang ;TI"Scounterpart(method name which does NOT end with <code>!</code>) of every bang ;TI"Omethod (method name which does end with <code>!</code>) that has does not ;TI"Umodify the receiver. This convention is typically true for ruby core libary but ;TI"4may/may not hold true for other ruby libraries.;T@
o;
;[I"RMethods that end with a question mark by convention return boolean. But they ;TI"Rmay not always return just +true+ or +false+.  Often they will may return an ;TI"9object to indicate a true value (or "truthy" value).;T@
o;
;[I"NMethods that end with an equals sign indicate an assignment method.  For ;TI"Passignment methods the return value is ignored, the arguments are returned ;TI"
instead.;T@
o;
;[I"KThese are method names for the various ruby operators.  Each of these ;TI"Poperators accept only one argument.  Following the operator is the typical ;TI"Ruse or name of the operator.  Creating an alternate meaning for the operator ;TI"Lmay lead to confusion as the user expects plus to add things, minus to ;TI"Qsubtract things, etc.  Additionally, you cannot alter the precedence of the ;TI"operators.;T@
o:RDoc::Markup::List:
@type:	NOTE:@items[o:RDoc::Markup::ListItem:@label[I"<code>+</code>   ;T;[o;
;[I"add;To;;[I"<code>-</code>   ;T;[o;
;[I"
subtract;To;;[I"<code>*</code>   ;T;[o;
;[I"
multiply;To;;[I"<code>**</code>  ;T;[o;
;[I"
power;To;;[I"<code>/</code>   ;T;[o;
;[I"divide;To;;[I"<code>%</code>   ;T;[o;
;[I"modulus division, String#%;To;;[I"<code>&</code>   ;T;[o;
;[I"AND;To;;[I"<code>^</code>   ;T;[o;
;[I"XOR (exclusive OR);To;;[I"<code>>></code>  ;T;[o;
;[I"right-shift;To;;[I"<code><<</code>  ;T;[o;
;[I"left-shift, append;To;;[I"<code>==</code>  ;T;[o;
;[I"
equal;To;;[I"<code>!=</code>  ;T;[o;
;[I"not equal;To;;[I"<code>===</code> ;T;[o;
;[I"#case equality.  See Object#===;To;;[I"<code>=~</code>  ;T;[o;
;[I"7pattern match.  (Not just for regular expressions);To;;[I"<code>!~</code>  ;T;[o;
;[I"does not match;To;;[I"<code><=></code> ;T;[o;
;[I"7comparison aka spaceship operator.  See Comparable;To;;[I"<code><</code>   ;T;[o;
;[I"less-than;To;;[I"<code><=</code>  ;T;[o;
;[I"less-than or equal;To;;[I"<code>></code>   ;T;[o;
;[I"greater-than;To;;[I"<code>>=</code>  ;T;[o;
;[I"greater-than or equal;T@
o;
;[I"TTo define unary methods minus, plus, tilde and not (<code>!</code>) follow the ;TI"Noperator with an <code>@</code> as in <code>+@</code> or <code>!@</code>:;T@
o;;[I"
class C
;TI"  def -@
;TI")    puts "you inverted this object"
;TI"  end
;TI"	end
;TI"
;TI"obj = C.new
;TI"
;TI".-obj # prints "you inverted this object"
;T;0o;
;[I")Unary methods accept zero arguments.;T@
o;
;[I"PAdditionally, methods for element reference and assignment may be defined: ;TI"R<code>[]</code> and <code>[]=</code> respectively. Both can take one or more ;TI"4arguments, and element reference can take none.;T@
o;;[I"
class C
;TI"  def [](a, b)
;TI"    puts a + b
;TI"  end
;TI"
;TI"  def []=(a, b, c)
;TI"    puts a * b + c
;TI"  end
;TI"	end
;TI"
;TI"obj = C.new
;TI"
;TI" obj[2, 3]     # prints "5"
;TI"!obj[2, 3] = 4 # prints "10"
;T;0S;	;
i;I"Return Values;T@
o;
;[	I"UBy default, a method returns the last expression that was evaluated in the body ;TI"Tof the method.  In the example above, the last (and only) expression evaluated ;TI"Qwas the simple sum <code>1 + 1</code>.  The +return+ keyword can be used to ;TI"4make it explicit that a method returns a value.;T@
o;;[I"def one_plus_one
;TI"  return 1 + 1
;TI"	end
;T;0o;
;[I"OIt can also be used to make a method return before the last expression is ;TI"evaluated.;T@
o;;[	I"def two_plus_two
;TI"  return 2 + 2
;TI"3  1 + 1  # this expression is never evaluated
;TI"	end
;T;0o;
;[I"ONote that for assignment methods the return value will always be ignored. ;TI"+Instead the argument will be returned:;T@
o;;[
I"def a=(value)
;TI"  return 1 + value
;TI"	end
;TI"
;TI"p(a = 5) # prints 5
;T;0S;	;
i;I"
Scope;T@
o;
;[I",The standard syntax to define a method:;T@
o;;[I"def my_method
;TI"
  # ...
;TI"	end
;T;0o;
;[I"Radds the method to a class.  You can define an instance method on a specific ;TI"$class with the +class+ keyword:;T@
o;;[
I"
class C
;TI"  def my_method
;TI"    # ...
;TI"  end
;TI"	end
;T;0o;
;[I"TA method may be defined on another object.  You may define a "class method" (a ;TI"Rmethod that is defined on the class, not an instance of the class) like this:;T@
o;;[
I"
class C
;TI"  def self.my_method
;TI"    # ...
;TI"  end
;TI"	end
;T;0o;
;[I"THowever, this is simply a special case of a greater syntactical power in Ruby, ;TI"Othe ability to add methods to any object.  Classes are objects, so adding ;TI"@class methods is simply adding methods to the Class object.;T@
o;
;[I"?The syntax for adding a method to an object is as follows:;T@
o;;[I"greeting = "Hello"
;TI"
;TI"def greeting.broaden
;TI"  self + ", world!"
;TI"	end
;TI"
;TI"0greeting.broaden # returns "Hello, world!"
;T;0o;
;[	I"M+self+ is a keyword referring to the current object under consideration ;TI"Mby the compiler, which might make the use of +self+ in defining a class ;TI"Mmethod above a little clearer.  Indeed, the example of adding a +hello+ ;TI"8method to the class +String+ can be rewritten thus:;T@
o;;[I"def String.hello
;TI"  "Hello, world!"
;TI"	end
;T;0o;
;[I"UA method defined like this is called a "singleton method".  +broaden+ will only ;TI"Uexist on the string instance +greeting+.  Other strings will not have +broaden+.;T@
S;	;
i;I"Overriding;T@
o;
;[
I"TWhen Ruby encounters the +def+ keyword, it doesn't consider it an error if the ;TI"Dmethod already exists: it simply redefines it.  This is called ;TI"N_overriding_.  Rather like extending core classes, this is a potentially ;TI"Udangerous ability, and should be used sparingly because it can cause unexpected ;TI"6results.  For example, consider this irb session:;T@
o;;[I">> "43".to_i
;TI"=> 43
;TI">> class String
;TI">>   def to_i
;TI">>     42
;TI">>   end
;TI">> end
;TI"=> nil
;TI">> "43".to_i
;TI"=> 42
;T;0o;
;[I"KThis will effectively sabotage any code which makes use of the method ;TI"<<code>String#to_i</code> to parse numbers from strings.;T@
S;	;
i;I"Arguments;T@
o;
;[I"OA method may accept arguments.  The argument list follows the method name:;T@
o;;[I"def add_one(value)
;TI"  value + 1
;TI"	end
;T;0o;
;[	I"RWhen called, the user of the +add_one+ method must provide an argument.  The ;TI"Targument is a local variable in the method body.  The method will then add one ;TI"Kto this argument and return the value.  If given +1+ this method will ;TI"return +2+.;T@
o;
;[I"7The parentheses around the arguments are optional:;T@
o;;[I"def add_one value
;TI"  value + 1
;TI"	end
;T;0o;
;[I"1Multiple arguments are separated by a comma:;T@
o;;[I"def add_values(a, b)
;TI"
  a + b
;TI"	end
;T;0o;
;[I"OWhen called, the arguments must be provided in the exact order.  In other ;TI")words, the arguments are positional.;T@
S;	;
i;I"Default Values;T@
o;
;[I"'Arguments may have default values:;T@
o;;[I"def add_values(a, b = 1)
;TI"
  a + b
;TI"	end
;T;0o;
;[I"RThe default value does not need to appear first, but arguments with defaults ;TI"+must be grouped together.  This is ok:;T@
o;;[I"%def add_values(a = 1, b = 2, c)
;TI"  a + b + c
;TI"	end
;T;0o;
;[I"#This will raise a SyntaxError:;T@
o;;[I"%def add_values(a = 1, b, c = 1)
;TI"  a + b + c
;TI"	end
;T;0S;	;
i;I"Array Decomposition;T@
o;
;[I"LYou can decompose (unpack or extract values from) an Array using extra ;TI""parentheses in the arguments:;T@
o;;[
I"def my_method((a, b))
;TI"  p a: a, b: b
;TI"	end
;TI"
;TI"my_method([1, 2])
;T;0o;
;[I"This prints:;T@
o;;[I"{:a=>1, :b=>2}
;T;0o;
;[I"JIf the argument has extra elements in the Array they will be ignored:;T@
o;;[
I"def my_method((a, b))
;TI"  p a: a, b: b
;TI"	end
;TI"
;TI"my_method([1, 2, 3])
;T;0o;
;[I"'This has the same output as above.;T@
o;
;[I"SYou can use a <code>*</code> to collect the remaining arguments.  This splits ;TI"0an Array into a first element and the rest:;T@
o;;[
I"def my_method((a, *b))
;TI"  p a: a, b: b
;TI"	end
;TI"
;TI"my_method([1, 2, 3])
;T;0o;
;[I"This prints:;T@
o;;[I"{:a=>1, :b=>[2, 3]}
;T;0o;
;[I"QThe argument will be decomposed if it responds to #to_ary.  You should only ;TI"Ddefine #to_ary if you can use your object in place of an Array.;T@
o;
;[I"OUse of the inner parentheses only uses one of the sent arguments.  If the ;TI"Oargument is not an Array it will be assigned to the first argument in the ;TI"Rdecomposition and the remaining arguments in the decomposition will be +nil+:;T@
o;;[
I"!def my_method(a, (b, c), d)
;TI"   p a: a, b: b, c: c, d: d
;TI"	end
;TI"
;TI"my_method(1, 2, 3)
;T;0o;
;[I"This prints:;T@
o;;[I"${:a=>1, :b=>2, :c=>nil, :d=>3}
;T;0o;
;[I",You can nest decomposition arbitrarily:;T@
o;;[I" def my_method(((a, b), c))
;TI"
  # ...
;TI"	end
;T;0S;	;
i;I"Array/Hash Argument;T@
o;
;[I"TPrefixing an argument with <code>*</code> causes any remaining arguments to be ;TI"converted to an Array:;T@
o;;[
I"&def gather_arguments(*arguments)
;TI"  p arguments
;TI"	end
;TI"
;TI"1gather_arguments 1, 2, 3 # prints [1, 2, 3]
;T;0o;
;[I"TThe array argument must be the last positional argument, it must appear before ;TI"any keyword arguments.;T@
o;
;[I"TThe array argument will capture a Hash as the last entry if a hash was sent by ;TI"/the caller after all positional arguments.;T@
o;;[I"4gather_arguments 1, a: 2 # prints [1, {:a=>2}]
;T;0o;
;[I"THowever, this only occurs if the method does not declare any keyword arguments.;T@
o;;[I"=def gather_arguments_keyword(*positional, keyword: nil)
;TI"1 p positional: positional, keyword: keyword
;TI"	end
;TI"
;TI"-gather_arguments_keyword 1, 2, three: 3
;TI"8#=> raises: unknown keyword: three (ArgumentError)
;T;0o;
;[I"KAlso, note that a bare <code>*</code> can be used to ignore arguments:;T@
o;;[I"def ignore_arguments(*)
;TI"	end
;T;0S;	;
i;I"Keyword Arguments;T@
o;
;[I"OKeyword arguments are similar to positional arguments with default values:;T@
o;;[I")def add_values(first: 1, second: 2)
;TI"  first + second
;TI"	end
;T;0o;
;[I"GArbitrary keyword arguments will be accepted with <code>**</code>:;T@
o;;[I".def gather_arguments(first: nil, **rest)
;TI"  p first, rest
;TI"	end
;TI"
;TI"4gather_arguments first: 1, second: 2, third: 3
;TI"-# prints 1 then {:second=>2, :third=>3}
;T;0o;
;[I"RWhen calling a method with keyword arguments the arguments may appear in any ;TI"Sorder.  If an unknown keyword argument is sent by the caller an ArgumentError ;TI"is raised.;T@
o;
;[I"LWhen mixing keyword arguments and positional arguments, all positional ;TI"8arguments must appear before any keyword arguments.;T@
S;	;
i;I"Block Argument;T@
o;
;[I"JThe block argument is indicated by <code>&</code> and must come last:;T@
o;;[I"def my_method(&my_block)
;TI"  my_block.call(self)
;TI"	end
;T;0o;
;[I"RMost frequently the block argument is used to pass a block to another method:;T@
o;;[I"def each_item(&block)
;TI"  @items.each(&block)
;TI"	end
;T;0o;
;[	I"RIf you are only going to call the block and will not otherwise manipulate it ;TI"Oor send it to another method using <code>yield</code> without an explicit ;TI"Rblock parameter is preferred.  This method is equivalent to the first method ;TI"in this section:;T@
o;;[I"def my_method
;TI"  yield self
;TI"	end
;T;0o;
;[	I"OThere is also a performance benefit to using yield over a calling a block ;TI"Rparameter.  When a block argument is assigned to a variable a Proc object is ;TI"Ncreated which holds the block.  When using yield this Proc object is not ;TI"
created.;T@
o;
;[I"RIf you only need to use the block sometimes you can use Proc.new to create a ;TI"Sproc from the block that was passed to your method.  See Proc.new for further ;TI"
details.;T@
S;	;
i;I"Exception Handling;T@
o;
;[I"PMethods have an implied exception handling block so you do not need to use ;TI"2+begin+ or +end+ to handle exceptions.  This:;T@
o;;[I"def my_method
;TI"
  begin
;TI",    # code that may raise an exception
;TI"  rescue
;TI"    # handle exception
;TI"  end
;TI"	end
;T;0o;
;[I"May be written as:;T@
o;;[
I"def my_method
;TI"*  # code that may raise an exception
;TI"rescue
;TI"  # handle exception
;TI"	end
;T;0o;
;[I"UIf you wish to rescue an exception for only part of your method use +begin+ and ;TI"9+end+.  For more details see the page on {exception ;TI"0handling}[rdoc-ref:syntax/exceptions.rdoc].;T:
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