Ruby Flashcards
alias
alias :newname :oldname
Creates an alias/ second name for the method.
Thus, method defined for newname and oldname are
the same.
BEGIN
BEGIN {
` some code `
}
begin
begin
` #some code `
rescue
` #some code `
ensure
` #some code `
end
module
Creates an interface/helper that allows code to
from the module to be executed in any
other ruby files that require
the module.
next
Jumps to the next iteration in the
most internal loop.
case
case number
when 0...3
` some code`
when 4
` some code`
else
` some code`
end
Equivalent of switch statement.
defined?
Checks whether an expression is defined.
Returns false if expression isn’t defined.
retry
If retry appears in rescue clause of begin expression, restart from the beginning of the begin body.
If retry appears in the iterator, the block, or the body of the for expression, restarts the invocation of the iterator call.
redo
Restarts the iteration of the most internal loop.
then
Optional keyword for if statements.
i.e
if john == jack then
puts "John and Jack are twins"
end
undef
Cancels the method definition. Undef can not appear in the method body. By using undef and alias, the interface of the class can be modified independently from the superclass, but notice it may be broke programs by the internal method call to self.
unless
unless $baby feed\_meat else feed\_milk end
unless expressions are used for reverse conditional execution. It is equivalent to:
if !(cond) ... else ... end
until
Examples:
until sunrise sleep end
Syntax:
until expr [do] ... end
Executes body until condition expression returns true.
i.e. work until tired
yield
Examples:
yield data
Syntax:
yield `(' [expr [`,' expr...]]) yield [expr [`,' expr...]]
Evaluates the block given to the current method with arguments, if no argument is given, nil is used as an argument. The argument assignment to the block parameter is done just like multiple assignment. If the block is not supplied for the current method, the exception is raised.
\a
A backslash escape
The BEL character. Rings the console bell.
\b
A backslash escape for the Backspace character.
\f
A backslash escape for the Form Feed character. Using a page break sends a Form Feed character
A Form Feed character forces the printer to eject the current page and to continue printing at the top of another. Often, it will also cause a carriage return.
\n
The escape sequence for the Newline character.
\v
The escape sequence for the vertical tab character.
\r
The escape sequence for the Carriage Return character.
::
(two colons)
The :: is a unary operator that allows: constants, instance methods and class methods defined within a class or module, to be accessed from anywhere outside the class or module.
===
(three equals)
Used to test equality within a when clause of a case statement.
i.e. (1…10) === 5 returns true.
**
Exponentiation
<<
>>
Binary left and right shift operators
i.e. a= 0011
a << 2
^
Binary XOR Operator copies the bit if it is set in one operand but not both.
a = 1100
b = 1010
(a^b) = 0110
~
Binary Ones Complement Operator is unary and has the efect of ‘flipping’ bits.
a = 0101 0011
~a = 1010 1100
&
Binary AND Operator copies a bit to the result if it exists in both operands.
a = 0101
b = 0100
a&b = 0100
|
(pipe)
Binary OR Operator copies a bit if it exists in either operand.
a = 0101
b= 0110
a|b = 0111
<=>
Combined comparison operator. Returns 0 if first operand equals second, 1 if first operand is greater than the second and -1 if first operand is less than the second.
