Returns first n
elements from the array.
If a negative number is given, raises an ArgumentError
.
See also Array#drop
a = [1, 2, 3, 4, 5, 0] a.take(3) #=> [1, 2, 3]
The primary interface to this library. Use to setup delegation when defining your class.
class MyClass < DelegateClass(ClassToDelegateTo) # Step 1 def initialize super(obj_of_ClassToDelegateTo) # Step 2 end end
Here’s a sample of use from Tempfile
which is really a File
object with a few special rules about storage location and when the File
should be deleted. That makes for an almost textbook perfect example of how to use delegation.
class Tempfile < DelegateClass(File) # constant and class member data initialization... def initialize(basename, tmpdir=Dir::tmpdir) # build up file path/name in var tmpname... @tmpfile = File.open(tmpname, File::RDWR|File::CREAT|File::EXCL, 0600) # ... super(@tmpfile) # below this point, all methods of File are supported... end # ... end
Mark the object as tainted.
Objects that are marked as tainted will be restricted from various built-in methods. This is to prevent insecure data, such as command-line arguments or strings read from Kernel#gets
, from inadvertently compromising the user’s system.
To check whether an object is tainted, use tainted?
.
You should only untaint a tainted object if your code has inspected it and determined that it is safe. To do so use untaint
.
Yields self to the block, and then returns self. The primary purpose of this method is to “tap into” a method chain, in order to perform operations on intermediate results within the chain.
(1..10) .tap {|x| puts "original: #{x}" } .to_a .tap {|x| puts "array: #{x}" } .select {|x| x.even? } .tap {|x| puts "evens: #{x}" } .map {|x| x*x } .tap {|x| puts "squares: #{x}" }
Returns int
truncated (toward zero) to a precision of ndigits
decimal digits (default: 0).
When the precision is negative, the returned value is an integer with at least ndigits.abs
trailing zeros.
Returns self
when ndigits
is zero or positive.
1.truncate #=> 1 1.truncate(2) #=> 1 18.truncate(-1) #=> 10 (-18).truncate(-1) #=> -10
Returns self.
Returns 1.
Returns the value as a rational. The optional argument eps
is always ignored.
Returns a complex object which denotes the given rectangular form.
Complex.rectangular(1, 2) #=> (1+2i)
Returns the numerator.
1 2 3+4i <- numerator - + -i -> ---- 2 3 6 <- denominator c = Complex('1/2+2/3i') #=> ((1/2)+(2/3)*i) n = c.numerator #=> (3+4i) d = c.denominator #=> 6 n / d #=> ((1/2)+(2/3)*i) Complex(Rational(n.real, d), Rational(n.imag, d)) #=> ((1/2)+(2/3)*i)
See denominator.
Returns the denominator (lcm of both denominator - real and imag).
See numerator.
Returns the value as a rational if possible (the imaginary part should be exactly zero).
Complex(1.0/3, 0).rationalize #=> (1/3) Complex(1, 0.0).rationalize # RangeError Complex(1, 2).rationalize # RangeError
See to_r.
Returns zero as a rational. The optional argument eps
is always ignored.
Returns an array; [num, 0].
Returns self.
Returns num
truncated (toward zero) to a precision of ndigits
decimal digits (default: 0).
Numeric
implements this by converting its value to a Float
and invoking Float#truncate
.
Returns true
if num
is less than 0.
Returns the numerator.
Returns the denominator (always positive).
Converts pattern to a Regexp
(if it isn’t already one), then invokes its match
method on str. If the second parameter is present, it specifies the position in the string to begin the search.
'hello'.match('(.)\1') #=> #<MatchData "ll" 1:"l"> 'hello'.match('(.)\1')[0] #=> "ll" 'hello'.match(/(.)\1/)[0] #=> "ll" 'hello'.match(/(.)\1/, 3) #=> nil 'hello'.match('xx') #=> nil
If a block is given, invoke the block with MatchData
if match succeed, so that you can write
str.match(pat) {|m| ...}
instead of
if m = str.match(pat) ... end
The return value is a value from block execution in this case.
Converts pattern to a Regexp
(if it isn’t already one), then returns a true
or false
indicates whether the regexp is matched str or not without updating $~
and other related variables. If the second parameter is present, it specifies the position in the string to begin the search.
"Ruby".match?(/R.../) #=> true "Ruby".match?(/R.../, 1) #=> false "Ruby".match?(/P.../) #=> false $& #=> nil