Results for: "module_function"

Hash#select!

With a block given, calls the block with each entry’s key and value; removes from self each entry for which the block returns false or nil.

Returns self if any entries were removed, nil otherwise:

h = {foo: 0, bar: 1, baz: 2}
h.select! {|key, value| value < 2 } # => {foo: 0, bar: 1}
h.select! {|key, value| value < 2 } # => nil

With no block given, returns a new Enumerator.

Related: see Methods for Deleting.

ENV::select

Yields each environment variable name and its value as a 2-element Array, returning a Hash of the names and values for which the block returns a truthy value:

ENV.replace('foo' => '0', 'bar' => '1', 'baz' => '2')
ENV.select { |name, value| name.start_with?('b') } # => {"bar"=>"1", "baz"=>"2"}
ENV.filter { |name, value| name.start_with?('b') } # => {"bar"=>"1", "baz"=>"2"}

Returns an Enumerator if no block given:

e = ENV.select # => #<Enumerator: {"bar"=>"1", "baz"=>"2", "foo"=>"0"}:select>
e.each { |name, value | name.start_with?('b') } # => {"bar"=>"1", "baz"=>"2"}
e = ENV.filter # => #<Enumerator: {"bar"=>"1", "baz"=>"2", "foo"=>"0"}:filter>
e.each { |name, value | name.start_with?('b') } # => {"bar"=>"1", "baz"=>"2"}

Yields each environment variable name and its value as a 2-element Array, deleting each entry for which the block returns false or nil, and returning ENV if any deletions made, or nil otherwise:

ENV.replace('foo' => '0', 'bar' => '1', 'baz' => '2')
ENV.select! { |name, value| name.start_with?('b') } # => ENV
ENV # => {"bar"=>"1", "baz"=>"2"}
ENV.select! { |name, value| true } # => nil

ENV.replace('foo' => '0', 'bar' => '1', 'baz' => '2')
ENV.filter! { |name, value| name.start_with?('b') } # => ENV
ENV # => {"bar"=>"1", "baz"=>"2"}
ENV.filter! { |name, value| true } # => nil

Returns an Enumerator if no block given:

ENV.replace('foo' => '0', 'bar' => '1', 'baz' => '2')
e = ENV.select! # => #<Enumerator: {"bar"=>"1", "baz"=>"2"}:select!>
e.each { |name, value| name.start_with?('b') } # => ENV
ENV # => {"bar"=>"1", "baz"=>"2"}
e.each { |name, value| true } # => nil

ENV.replace('foo' => '0', 'bar' => '1', 'baz' => '2')
e = ENV.filter! # => #<Enumerator: {"bar"=>"1", "baz"=>"2"}:filter!>
e.each { |name, value| name.start_with?('b') } # => ENV
ENV # => {"bar"=>"1", "baz"=>"2"}
e.each { |name, value| true } # => nil

Ractor::select

TBD

Ractor#monitor

Register port as a monitoring port. If the ractor terminated, the port received a Symbol object. :exited will be sent if the ractor terminated without an exception. :aborted will be sent if the ractor terminated with a exception.

r = Ractor.new{ some_task() }
r.monitor(port = Ractor::Port.new)
port.receive #=> :exited and r is terminated

r = Ractor.new{ raise "foo" }
r.monitor(port = Ractor::Port.new)
port.receive #=> :terminated and r is terminated with an exception "foo"

Kernel#select

Invokes system call select(2), which monitors multiple file descriptors, waiting until one or more of the file descriptors becomes ready for some class of I/O operation.

Not implemented on all platforms.

Each of the arguments read_ios, write_ios, and error_ios is an array of IO objects.

Argument timeout is a numeric value (such as integer or float) timeout interval in seconds. timeout can also be nil or Float::INFINITY. nil and Float::INFINITY means no timeout.

The method monitors the IO objects given in all three arrays, waiting for some to be ready; returns a 3-element array whose elements are:

An array of the objects in read_ios that are ready for reading.
An array of the objects in write_ios that are ready for writing.
An array of the objects in error_ios have pending exceptions.

If no object becomes ready within the given timeout, nil is returned.

IO.select peeks the buffer of IO objects for testing readability. If the IO buffer is not empty, IO.select immediately notifies readability. This “peek” only happens for IO objects. It does not happen for IO-like objects such as OpenSSL::SSL::SSLSocket.

The best way to use IO.select is invoking it after non-blocking methods such as read_nonblock, write_nonblock, etc. The methods raise an exception which is extended by IO::WaitReadable or IO::WaitWritable. The modules notify how the caller should wait with IO.select. If IO::WaitReadable is raised, the caller should wait for reading. If IO::WaitWritable is raised, the caller should wait for writing.

So, blocking read (readpartial) can be emulated using read_nonblock and IO.select as follows:

begin
  result = io_like.read_nonblock(maxlen)
rescue IO::WaitReadable
  IO.select([io_like])
  retry
rescue IO::WaitWritable
  IO.select(nil, [io_like])
  retry
end

Especially, the combination of non-blocking methods and IO.select is preferred for IO like objects such as OpenSSL::SSL::SSLSocket. It has to_io method to return underlying IO object. IO.select calls to_io to obtain the file descriptor to wait.

This means that readability notified by IO.select doesn’t mean readability from OpenSSL::SSL::SSLSocket object.

The most likely situation is that OpenSSL::SSL::SSLSocket buffers some data. IO.select doesn’t see the buffer. So IO.select can block when OpenSSL::SSL::SSLSocket#readpartial doesn’t block.

However, several more complicated situations exist.

SSL is a protocol which is sequence of records. The record consists of multiple bytes. So, the remote side of SSL sends a partial record, IO.select notifies readability but OpenSSL::SSL::SSLSocket cannot decrypt a byte and OpenSSL::SSL::SSLSocket#readpartial will block.

Also, the remote side can request SSL renegotiation which forces the local SSL engine to write some data. This means OpenSSL::SSL::SSLSocket#readpartial may invoke write system call and it can block. In such a situation, OpenSSL::SSL::SSLSocket#read_nonblock raises IO::WaitWritable instead of blocking. So, the caller should wait for ready for writability as above example.

The combination of non-blocking methods and IO.select is also useful for streams such as tty, pipe socket socket when multiple processes read from a stream.

Finally, Linux kernel developers don’t guarantee that readability of select(2) means readability of following read(2) even for a single process; see select(2)

Invoking IO.select before IO#readpartial works well as usual. However it is not the best way to use IO.select.

The writability notified by select(2) doesn’t show how many bytes are writable. IO#write method blocks until given whole string is written. So, IO#write(two or more bytes) can block after writability is notified by IO.select. IO#write_nonblock is required to avoid the blocking.

Blocking write (write) can be emulated using write_nonblock and IO.select as follows: IO::WaitReadable should also be rescued for SSL renegotiation in OpenSSL::SSL::SSLSocket.

while 0 < string.bytesize
  begin
    written = io_like.write_nonblock(string)
  rescue IO::WaitReadable
    IO.select([io_like])
    retry
  rescue IO::WaitWritable
    IO.select(nil, [io_like])
    retry
  end
  string = string.byteslice(written..-1)
end

Example:

rp, wp = IO.pipe
mesg = "ping "
100.times {
  # IO.select follows IO#read.  Not the best way to use IO.select.
  rs, ws, = IO.select([rp], [wp])
  if r = rs[0]
    ret = r.read(5)
    print ret
    case ret
    when /ping/
      mesg = "pong\n"
    when /pong/
      mesg = "ping "
    end
  end
  if w = ws[0]
    w.write(mesg)
  end
}

Output:

ping pong
ping pong
ping pong
(snipped)
ping

Enumerable#select

Returns an array containing elements selected by the block.

With a block given, calls the block with successive elements; returns an array of those elements for which the block returns a truthy value:

(0..9).select {|element| element % 3 == 0 } # => [0, 3, 6, 9]
a = {foo: 0, bar: 1, baz: 2}.select {|key, value| key.start_with?('b') }
a # => {:bar=>1, :baz=>2}

With no block given, returns an Enumerator.

Related: reject.

Enumerable#collect

Returns an array of objects returned by the block.

With a block given, calls the block with successive elements; returns an array of the objects returned by the block:

(0..4).map {|i| i*i }                               # => [0, 1, 4, 9, 16]
{foo: 0, bar: 1, baz: 2}.map {|key, value| value*2} # => [0, 2, 4]

With no block given, returns an Enumerator.

Digest::hexencode

Generates a hex-encoded version of a given string.

Process::daemon

Detaches the current process from its controlling terminal and runs it in the background as system daemon; returns zero.

By default:

Changes the current working directory to the root directory.
Redirects $stdin, $stdout, and $stderr to the null device.

If optional argument nochdir is true, does not change the current working directory.

If optional argument noclose is true, does not redirect $stdin, $stdout, or $stderr.

ObjectSpace::trace_object_allocations_clear

Clear recorded tracing information.

DidYouMean::TreeSpellChecker#dictionary_without_leaves

No documentation available

Gem::Command::add_common_option

No documentation available

Net::HTTPGenericRequest#encode_multipart_form_data

No documentation available

Enumerator::Lazy#_enumerable_collect

Like Enumerable#map, but chains operation to be lazy-evaluated.

(1..Float::INFINITY).lazy.map {|i| i**2 }
#=> #<Enumerator::Lazy: #<Enumerator::Lazy: 1..Infinity>:map>
(1..Float::INFINITY).lazy.map {|i| i**2 }.first(3)
#=> [1, 4, 9]

Enumerator::Lazy#_enumerable_select

Like Enumerable#select, but chains operation to be lazy-evaluated.

Net::HTTPResponse#body_encoding=

Sets the encoding that should be used when reading the body:

If the given value is an Encoding object, that encoding will be used.
Otherwise if the value is a string, the value of Encoding#find(value) will be used.
Otherwise an encoding will be deduced from the body itself.

Examples:

http = Net::HTTP.new(hostname)
req = Net::HTTP::Get.new('/')

http.request(req) do |res|
  p res.body.encoding # => #<Encoding:ASCII-8BIT>
end

http.request(req) do |res|
  res.body_encoding = "UTF-8"
  p res.body.encoding # => #<Encoding:UTF-8>
end

DidYouMean::TreeSpellChecker#plausible_dimensions

No documentation available

Gem::Resolver#amount_constrained

returns an integer in (-infty, 0] a number closer to 0 means the dependency is less constraining

dependencies w/ 0 or 1 possibilities (ignoring version requirements) are given very negative values, so they always sort first, before dependencies that are unconstrained

Fiber::Scheduler#io_select

Invoked by IO.select to ask whether the specified descriptors are ready for specified events within the specified timeout.

Expected to return the 3-tuple of Array of IOs that are ready.

OpenURI::Meta#content_encoding

Returns a list of encodings in Content-Encoding field as an array of strings.

The encodings are downcased for canonicalization.

Gem::BundlerVersionFinder::lockfile_version

No documentation available

Object#remove_instance_variable

Removes the named instance variable from obj, returning that variable’s value. The name can be passed as a symbol or as a string.

class Dummy
  attr_reader :var
  def initialize
    @var = 99
  end
  def remove
    remove_instance_variable(:@var)
  end
end
d = Dummy.new
d.var      #=> 99
d.remove   #=> 99
d.var      #=> nil

Object#define_singleton_method

Defines a public singleton method in the receiver. The method parameter can be a Proc, a Method or an UnboundMethod object. If a block is specified, it is used as the method body. If a block or a method has parameters, they’re used as method parameters.

class A
  class << self
    def class_name
      to_s
    end
  end
end
A.define_singleton_method(:who_am_i) do
  "I am: #{class_name}"
end
A.who_am_i   # ==> "I am: A"

guy = "Bob"
guy.define_singleton_method(:hello) { "#{self}: Hello there!" }
guy.hello    #=>  "Bob: Hello there!"

chris = "Chris"
chris.define_singleton_method(:greet) {|greeting| "#{greeting}, I'm Chris!" }
chris.greet("Hi") #=> "Hi, I'm Chris!"

BasicObject#singleton_method_added

Invoked as a callback whenever a singleton method is added to the receiver.

module Chatty
  def Chatty.singleton_method_added(id)
    puts "Adding #{id.id2name}"
  end
  def self.one()     end
  def two()          end
  def Chatty.three() end
end

produces:

Adding singleton_method_added
Adding one
Adding three