We provide you with all the mostly used Ruby modules and corresponding function and feature list. You can click on the feature and see more details about the feature with example code. We hope you will enjoy the cheat sheet and developer hints very much.
Arrays are ordered, integer-indexed collections of any object.
Array indexing starts at 0, as in C or Java. A negative index is assumed to be relative to the end of the array---that is, an index of -1 indicates the last element of the array, -2 is the next to last element in the array, and so on.
BasicObject is the parent class of all classes in Ruby. It's an explicit blank class.
BasicObject can be used for creating object hierarchies independent of Ruby's object hierarchy, proxy objects like the Delegator class, or other uses where namespace pollution from Ruby's methods and classes must be avoided.
ENV is a hash-like accessor for environment variables.
When you get the value for a name in ENV, the value is retrieved from among the current environment variables.
When you create or set a name-value pair in ENV, the name and value are immediately set in the environment variables.
When you delete a name-value pair in ENV, it is immediately deleted from the environment variables.
A String.
An object that responds to #to_str by returning a String, in which case that String will be used as the name or value.
May not be the empty string:
May not contain character "=":
May not be a non-String that does not respond to #to_str:
May not contain the NUL character "\0":
May not have an ASCII-incompatible encoding such as UTF-16LE or ISO-2022-JP:
A Hash returned by an ENV method.
An Enumerator returned by an ENV method.
An Array returned by ::keys, ::values, or ::to_a.
The String returned by ::inspect.
The Array returned by ::shift.
The name returned by ::key.
A File is an abstraction of any file object
accessible by the program and is closely associated with class IO. File includes the methods
of module FileTest as class methods, allowing
you to write (for example) File.exist?("foo").
In the description of File methods, permission bits are a platform-specific set of bits that indicate permissions of a file. On Unix-based systems, permissions are viewed as a set of three octets, for the owner, the group, and the rest of the world. For each of these entities, permissions may be set to read, write, or execute the file:
Float objects represent inexact real numbers using the native architecture's double-precision floating point representation.
Floating point has a different arithmetic and is an inexact number. So you should know its esoteric system. See following:
docs.sun.com/source/806-3568/ncg_goldberg.html
github.com/rdp/ruby_tutorials_core/wiki/Ruby-Talk-FAQ#floats_imprecise
A Hash is a dictionary-like collection of unique keys and their values. Also called associative arrays, they are similar to Arrays, but where an Array uses integers as its index, a Hash allows you to use any object type.
Hashes enumerate their values in the order that the corresponding keys were inserted.
The IO class is the basis for all input and output in Ruby. An I/O stream may be duplexed (that is, bidirectional), and so may use more than one native operating system stream.
Many of the examples in this section use the File class, the only standard subclass of IO. The two classes are closely associated. Like the File class, the Socket library subclasses from IO (such as TCPSocket or UDPSocket).
A plain string represents a filename suitable for the underlying operating system.
A string starting with "|" indicates a subprocess.
The remainder of the string following the "|" is
invoked as a process with appropriate input/output channels connected to
it.
A string equal to "|-" will create another Ruby
instance as a subprocess.
IO::console
IO#raw
IO#raw!
IO#cooked
IO#cooked!
IO#getch
IO#echo=
IO#echo?
IO#noecho
IO#winsize
IO#winsize=
IO#iflush
IO#ioflush
IO#oflush
Holds Integer values. You cannot add a singleton method to an Integer object, any attempt to do so will raise a TypeError.
The Kernel module is included by class Object, so its methods are available in every Ruby object.
The Kernel instance methods are documented in class Object while the module methods are documented here. These methods are called without a receiver and thus can be called in functional form:
Method objects are created by Object#method, and are associated with a particular object (not just with a class). They may be used to invoke the method within the object, and as a block associated with an iterator. They may also be unbound from one object (creating an UnboundMethod) and bound to another.
Numeric is the class from which all higher-level numeric classes should inherit.
Numeric allows instantiation of heap-allocated objects. Other core numeric classes such as Integer are implemented as immediates, which means that each Integer is a single immutable object which is always passed by value.
A Range represents an interval—a set of values
with a beginning and an end. Ranges may be constructed using the
s..e and
s...e literals, or with ::new. Ranges constructed using
.. run from the beginning to the end inclusively. Those
created using ... exclude the end value. When used as an
iterator, ranges return each value in the sequence.
begin of beginless range and end of endless range
are nil;
each of beginless range raises an exception;
each of endless range enumerates infinite sequence (may be
useful in combination with Enumerable#take_while or
similar methods);
(1..) and (1...) are not equal, although
technically representing the same sequence.
A String object holds and manipulates an arbitrary sequence of bytes, typically representing characters. String objects may be created using ::new or as literals.
Because of aliasing issues, users of strings should be aware of the methods that modify the contents of a String object. Typically, methods with names ending in “!” modify their receiver, while those without a “!” return a new String. However, there are exceptions, such as #[]=.
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