Marcos Dione: ruby-cheatsheet-for-pythonistas

module Foo  # this is the root of this namespace# everything defined here must be referenced as Foo::thing, as in
Foo::CamelCase::real_method():symbol# symbols are the simplest objects, wich only have a name and a unique value:'symbol with spaces!'"#{interpolated_expression}"# how to iterpolate expressions in strings/regular_expression/# very Perl-ish

generator { |item| block }  # this is related to yield%q{quote words}  # à la perl!%w{words}  # same?defclassless_method_aka_function(default=:value)# Ruby calls these methods too
    block  # ruby custom indents by 2!end

method_call :without :parensclassCamelCase<SuperClass# simple inheritanceinclude Bar  # this is a mixin;# Bar is a module and the class 'inherits' all its 'methods'

    public :real_method,:assign_method=
    protected :mutator_method!
    private :query_method?self# here is the class!defreal_method(*args)# splat argument, can be anywhere# no **kwargs?super# this calls SuperClass::real_method(*args)# comapre withsuper()# this calls SuperClass::real_method()!

        local_variable
        @instance_variable# always private@@class_variable# always private$global_variablereturn self# alternativelyself# as the implicit return value is the last statement executed# and all statements produce a valueenddef assign_method=()# conventionally for this kind of syntactic sugar:# When the interpreter sees the message "name" followed by " =",# it automatically ignores the space before the equal sign# and reads the single message "name=" -# a call to the method whose name is name=endclass<<self# this is in metaclass context!end

    protected
    def mutator_method!(a, *more, b)# conventionally this modifies the instanceend

    private
    def query_method?()# conventionally returns true/falseendend# extending classesclassCamelCase# do I need to respecify the inheritance here?defmore_methods()endend

obj.send(:method_name_as_symbol, args, ...)begin
    raise 'exceptions can be strings'rescueOneType=> e  # bind the exception to e# rescuedrescueAnotherType# alsoensure# finallyelse# fallbackend=beginLongcommentblocks!=end

statement; statement

long \
line

# everything is true exceptfalse# andnil

variable ||= default_value

`shell`

AConstant  # technically class names are constants# so do module names
A_CONSTANT  # conventionally; always public# The Ruby interpreter does not actually enforce the constancy of constants,# but it does issue a warning if a program changes the value of a constant# case is an expression
foo =casewhen true then100when false then200else300enddo|args; another_local_variable|# args are local variables of this block# whose scope ends with the block# and which can eclipse another variable of the same name# in the containing scope# another_local_variable is declared local but does not# consume parametersend

{ |args| ... }  # another block, conventionally single lined# Matz says that any method can be called with a block as an implicit argument.# Inside the method, you can call the block using the yield keyword with a value.# Matz is Joe Ruby# yield is not what python does# see http://rubylearning.com/satishtalim/ruby_blocks.html# block_given?

a= []# array
a[0] ==nilENV# hash holding envvarsARGV# array with CL arguments(1..10)# range(0...10)# python like5=== (1..10)# true, 'case equality operator'

{ :symbol => 'value' } == { symbol: 'value' }  # hashes, not blocks :)

lambda { ... }  # convert a block into a Proc object# you cannot pass methods into other methods (but you can pass Procs into methods),# and methods cannot return other methods (but they can return Procs).

load 'foo.rb'# #include likerequire'foo'# import, uses $:
require_relative 'bar'# import from local dir