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IVar.html
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IVar.html
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<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>
Class: Concurrent::IVar
— Concurrent Ruby
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<div id="content"><h1>Class: Concurrent::IVar
</h1>
<div class="box_info">
<dl>
<dt>Inherits:</dt>
<dd>
<span class="inheritName"><span class='object_link'>Synchronization::LockableObject</span></span>
<ul class="fullTree">
<li>Object</li>
<li class="next"><span class='object_link'>Synchronization::LockableObject</span></li>
<li class="next">Concurrent::IVar</li>
</ul>
<a href="#" class="inheritanceTree">show all</a>
</dd>
</dl>
<dl>
<dt>Includes:</dt>
<dd><span class='object_link'><a href="Concern/Obligation.html" title="Concurrent::Concern::Obligation (module)">Concern::Obligation</a></span>, <span class='object_link'><a href="Concern/Observable.html" title="Concurrent::Concern::Observable (module)">Concern::Observable</a></span></dd>
</dl>
<dl>
<dt>Defined in:</dt>
<dd>lib/concurrent/ivar.rb</dd>
</dl>
</div>
<h2>Overview</h2><div class="docstring">
<div class="discussion">
<p>An <code>IVar</code> is like a future that you can assign. As a future is a value that
is being computed that you can wait on, an <code>IVar</code> is a value that is waiting
to be assigned, that you can wait on. <code>IVars</code> are single assignment and
deterministic.</p>
<p>Then, express futures as an asynchronous computation that assigns an <code>IVar</code>.
The <code>IVar</code> becomes the primitive on which <a href="Future">futures</a> and
<a href="Dataflow">dataflow</a> are built.</p>
<p>An <code>IVar</code> is a single-element container that is normally created empty, and
can only be set once. The I in <code>IVar</code> stands for immutable. Reading an
<code>IVar</code> normally blocks until it is set. It is safe to set and read an <code>IVar</code>
from different threads.</p>
<p>If you want to have some parallel task set the value in an <code>IVar</code>, you want
a <code>Future</code>. If you want to create a graph of parallel tasks all executed
when the values they depend on are ready you want <code>dataflow</code>. <code>IVar</code> is
generally a low-level primitive.</p>
<h2>Examples</h2>
<p>Create, set and get an <code>IVar</code></p>
<pre class="code ruby"><code class="ruby"><span class='id identifier rubyid_ivar'>ivar</span> <span class='op'>=</span> <span class='const'><span class='object_link'><a href="../Concurrent.html" title="Concurrent (module)">Concurrent</a></span></span><span class='op'>::</span><span class='const'>IVar</span><span class='period'>.</span><span class='id identifier rubyid_new'><span class='object_link'><a href="#initialize-instance_method" title="Concurrent::IVar#initialize (method)">new</a></span></span>
<span class='id identifier rubyid_ivar'>ivar</span><span class='period'>.</span><span class='id identifier rubyid_set'>set</span> <span class='int'>14</span>
<span class='id identifier rubyid_ivar'>ivar</span><span class='period'>.</span><span class='id identifier rubyid_value'>value</span> <span class='comment'>#=> 14
</span><span class='id identifier rubyid_ivar'>ivar</span><span class='period'>.</span><span class='id identifier rubyid_set'>set</span> <span class='int'>2</span> <span class='comment'># would now be an error
</span></code></pre>
<h2>See Also</h2>
<ol>
<li>For the theory: Arvind, R. Nikhil, and K. Pingali.
<a href="http://dl.acm.org/citation.cfm?id=69562">I-Structures: Data structures for parallel computing</a>.
In Proceedings of Workshop on Graph Reduction, 1986.</li>
<li>For recent application:
<a href="http://www.cs.rice.edu/%7Evs3/hjlib/doc/edu/rice/hj/api/HjDataDrivenFuture.html">DataDrivenFuture in Habanero Java from Rice</a>.</li>
</ol>
</div>
</div>
<div class="tags">
</div><div id="subclasses">
<h2>Direct Known Subclasses</h2>
<p class="children"><span class='object_link'><a href="Future.html" title="Concurrent::Future (class)">Future</a></span>, <span class='object_link'><a href="Promise.html" title="Concurrent::Promise (class)">Promise</a></span>, <span class='object_link'><a href="ScheduledTask.html" title="Concurrent::ScheduledTask (class)">ScheduledTask</a></span></p>
</div>
<h2>
Instance Method Summary
<small><a href="#" class="summary_toggle">collapse</a></small>
</h2>
<ul class="summary">
<li class="public ">
<span class="summary_signature">
<a href="#add_observer-instance_method" title="#add_observer (instance method)">#<strong>add_observer</strong>(observer = nil, func = :update, &block) ⇒ undocumented </a>
</span>
<span class="summary_desc"><div class='inline'><p>Add an observer on this object that will receive notification on update.</p>
</div></span>
</li>
<li class="public ">
<span class="summary_signature">
<a href="#complete%3F-instance_method" title="#complete? (instance method)">#<strong>complete?</strong> ⇒ Boolean </a>
</span>
<span class="note title not_defined_here">
included
from <span class='object_link'><a href="Concern/Obligation.html#complete%3F-instance_method" title="Concurrent::Concern::Obligation#complete? (method)">Concern::Obligation</a></span>
</span>
<span class="summary_desc"><div class='inline'><p>Has the obligation completed processing?.</p>
</div></span>
</li>
<li class="public ">
<span class="summary_signature">
<a href="#count_observers-instance_method" title="#count_observers (instance method)">#<strong>count_observers</strong> ⇒ Integer </a>
</span>
<span class="note title not_defined_here">
included
from <span class='object_link'><a href="Concern/Observable.html#count_observers-instance_method" title="Concurrent::Concern::Observable#count_observers (method)">Concern::Observable</a></span>
</span>
<span class="summary_desc"><div class='inline'><p>Return the number of observers associated with this object.</p>
</div></span>
</li>
<li class="public ">
<span class="summary_signature">
<a href="#delete_observer-instance_method" title="#delete_observer (instance method)">#<strong>delete_observer</strong>(observer) ⇒ Object </a>
</span>
<span class="note title not_defined_here">
included
from <span class='object_link'><a href="Concern/Observable.html#delete_observer-instance_method" title="Concurrent::Concern::Observable#delete_observer (method)">Concern::Observable</a></span>
</span>
<span class="summary_desc"><div class='inline'><p>Remove <code>observer</code> as an observer on this object so that it will no longer receive notifications.</p>
</div></span>
</li>
<li class="public ">
<span class="summary_signature">
<a href="#delete_observers-instance_method" title="#delete_observers (instance method)">#<strong>delete_observers</strong> ⇒ Observable </a>
</span>
<span class="note title not_defined_here">
included
from <span class='object_link'><a href="Concern/Observable.html#delete_observers-instance_method" title="Concurrent::Concern::Observable#delete_observers (method)">Concern::Observable</a></span>
</span>
<span class="summary_desc"><div class='inline'><p>Remove all observers associated with this object.</p>
</div></span>
</li>
<li class="public ">
<span class="summary_signature">
<a href="#exception-instance_method" title="#exception (instance method)">#<strong>exception</strong>(*args) ⇒ undocumented </a>
</span>
<span class="note title not_defined_here">
included
from <span class='object_link'><a href="Concern/Obligation.html#exception-instance_method" title="Concurrent::Concern::Obligation#exception (method)">Concern::Obligation</a></span>
</span>
<span class="summary_desc"><div class='inline'></div></span>
</li>
<li class="public ">
<span class="summary_signature">
<a href="#fail-instance_method" title="#fail (instance method)">#<strong>fail</strong>(reason = StandardError.new) ⇒ IVar </a>
</span>
<span class="summary_desc"><div class='inline'><p>Set the <code>IVar</code> to failed due to some error and wake or notify all threads waiting on it.</p>
</div></span>
</li>
<li class="public ">
<span class="summary_signature">
<a href="#fulfilled%3F-instance_method" title="#fulfilled? (instance method)">#<strong>fulfilled?</strong> ⇒ Boolean </a>
(also: #realized?)
</span>
<span class="note title not_defined_here">
included
from <span class='object_link'><a href="Concern/Obligation.html#fulfilled%3F-instance_method" title="Concurrent::Concern::Obligation#fulfilled? (method)">Concern::Obligation</a></span>
</span>
<span class="summary_desc"><div class='inline'><p>Has the obligation been fulfilled?.</p>
</div></span>
</li>
<li class="public ">
<span class="summary_signature">
<a href="#incomplete%3F-instance_method" title="#incomplete? (instance method)">#<strong>incomplete?</strong> ⇒ Boolean </a>
</span>
<span class="note title not_defined_here">
included
from <span class='object_link'><a href="Concern/Obligation.html#incomplete%3F-instance_method" title="Concurrent::Concern::Obligation#incomplete? (method)">Concern::Obligation</a></span>
</span>
<span class="summary_desc"><div class='inline'><p>Is the obligation still awaiting completion of processing?.</p>
</div></span>
</li>
<li class="public ">
<span class="summary_signature">
<a href="#initialize-instance_method" title="#initialize (instance method)">#<strong>initialize</strong>(value = NULL, opts = {}, &block) ⇒ IVar </a>
</span>
<span class="note title constructor">constructor</span>
<span class="summary_desc"><div class='inline'><p>Create a new <code>IVar</code> in the <code>:pending</code> state with the (optional) initial value.</p>
</div></span>
</li>
<li class="public ">
<span class="summary_signature">
<a href="#pending%3F-instance_method" title="#pending? (instance method)">#<strong>pending?</strong> ⇒ Boolean </a>
</span>
<span class="note title not_defined_here">
included
from <span class='object_link'><a href="Concern/Obligation.html#pending%3F-instance_method" title="Concurrent::Concern::Obligation#pending? (method)">Concern::Obligation</a></span>
</span>
<span class="summary_desc"><div class='inline'><p>Is obligation completion still pending?.</p>
</div></span>
</li>
<li class="public ">
<span class="summary_signature">
<a href="#reason-instance_method" title="#reason (instance method)">#<strong>reason</strong> ⇒ Exception </a>
</span>
<span class="note title not_defined_here">
included
from <span class='object_link'><a href="Concern/Obligation.html#reason-instance_method" title="Concurrent::Concern::Obligation#reason (method)">Concern::Obligation</a></span>
</span>
<span class="summary_desc"><div class='inline'><p>If an exception was raised during processing this will return the exception object.</p>
</div></span>
</li>
<li class="public ">
<span class="summary_signature">
<a href="#rejected%3F-instance_method" title="#rejected? (instance method)">#<strong>rejected?</strong> ⇒ Boolean </a>
</span>
<span class="note title not_defined_here">
included
from <span class='object_link'><a href="Concern/Obligation.html#rejected%3F-instance_method" title="Concurrent::Concern::Obligation#rejected? (method)">Concern::Obligation</a></span>
</span>
<span class="summary_desc"><div class='inline'><p>Has the obligation been rejected?.</p>
</div></span>
</li>
<li class="public ">
<span class="summary_signature">
<a href="#set-instance_method" title="#set (instance method)">#<strong>set</strong>(value = NULL) { ... } ⇒ IVar </a>
</span>
<span class="summary_desc"><div class='inline'><p>Set the <code>IVar</code> to a value and wake or notify all threads waiting on it.</p>
</div></span>
</li>
<li class="public ">
<span class="summary_signature">
<a href="#state-instance_method" title="#state (instance method)">#<strong>state</strong> ⇒ Symbol </a>
</span>
<span class="note title not_defined_here">
included
from <span class='object_link'><a href="Concern/Obligation.html#state-instance_method" title="Concurrent::Concern::Obligation#state (method)">Concern::Obligation</a></span>
</span>
<span class="summary_desc"><div class='inline'><p>The current state of the obligation.</p>
</div></span>
</li>
<li class="public ">
<span class="summary_signature">
<a href="#try_set-instance_method" title="#try_set (instance method)">#<strong>try_set</strong>(value = NULL) { ... } ⇒ Boolean </a>
</span>
<span class="summary_desc"><div class='inline'><p>Attempt to set the <code>IVar</code> with the given value or block.</p>
</div></span>
</li>
<li class="public ">
<span class="summary_signature">
<a href="#unscheduled%3F-instance_method" title="#unscheduled? (instance method)">#<strong>unscheduled?</strong> ⇒ Boolean </a>
</span>
<span class="note title not_defined_here">
included
from <span class='object_link'><a href="Concern/Obligation.html#unscheduled%3F-instance_method" title="Concurrent::Concern::Obligation#unscheduled? (method)">Concern::Obligation</a></span>
</span>
<span class="summary_desc"><div class='inline'><p>Is the obligation still unscheduled?.</p>
</div></span>
</li>
<li class="public ">
<span class="summary_signature">
<a href="#value-instance_method" title="#value (instance method)">#<strong>value</strong>(timeout = nil) ⇒ Object </a>
</span>
<span class="note title not_defined_here">
included
from <span class='object_link'><a href="Concern/Obligation.html#value-instance_method" title="Concurrent::Concern::Obligation#value (method)">Concern::Obligation</a></span>
</span>
<span class="summary_desc"><div class='inline'><p>The current value of the obligation.</p>
</div></span>
</li>
<li class="public ">
<span class="summary_signature">
<a href="#value!-instance_method" title="#value! (instance method)">#<strong>value!</strong>(timeout = nil) ⇒ Object </a>
</span>
<span class="note title not_defined_here">
included
from <span class='object_link'><a href="Concern/Obligation.html#value!-instance_method" title="Concurrent::Concern::Obligation#value! (method)">Concern::Obligation</a></span>
</span>
<span class="summary_desc"><div class='inline'><p>The current value of the obligation.</p>
</div></span>
</li>
<li class="public ">
<span class="summary_signature">
<a href="#wait-instance_method" title="#wait (instance method)">#<strong>wait</strong>(timeout = nil) ⇒ Obligation </a>
</span>
<span class="note title not_defined_here">
included
from <span class='object_link'><a href="Concern/Obligation.html#wait-instance_method" title="Concurrent::Concern::Obligation#wait (method)">Concern::Obligation</a></span>
</span>
<span class="summary_desc"><div class='inline'><p>Wait until obligation is complete or the timeout has been reached.</p>
</div></span>
</li>
<li class="public ">
<span class="summary_signature">
<a href="#wait!-instance_method" title="#wait! (instance method)">#<strong>wait!</strong>(timeout = nil) ⇒ Obligation </a>
(also: #no_error!)
</span>
<span class="note title not_defined_here">
included
from <span class='object_link'><a href="Concern/Obligation.html#wait!-instance_method" title="Concurrent::Concern::Obligation#wait! (method)">Concern::Obligation</a></span>
</span>
<span class="summary_desc"><div class='inline'><p>Wait until obligation is complete or the timeout is reached.</p>
</div></span>
</li>
<li class="public ">
<span class="summary_signature">
<a href="#with_observer-instance_method" title="#with_observer (instance method)">#<strong>with_observer</strong>(observer = nil, func = :update, &block) ⇒ Observable </a>
</span>
<span class="note title not_defined_here">
included
from <span class='object_link'><a href="Concern/Observable.html#with_observer-instance_method" title="Concurrent::Concern::Observable#with_observer (method)">Concern::Observable</a></span>
</span>
<span class="summary_desc"><div class='inline'><p>As <code>#add_observer</code> but can be used for chaining.</p>
</div></span>
</li>
</ul>
<div id="constructor_details" class="method_details_list">
<h2>Constructor Details</h2>
<div class="method_details first">
<h3 class="signature first" id="initialize-instance_method">
#<strong>initialize</strong>(value = NULL, opts = {}, &block) ⇒ <tt><span class='object_link'><a href="" title="Concurrent::IVar (class)">IVar</a></span></tt>
</h3><div class="docstring">
<div class="discussion">
<p>Create a new <code>IVar</code> in the <code>:pending</code> state with the (optional) initial value.</p>
</div>
</div>
<div class="tags">
<p class="tag_title">Parameters:</p>
<ul class="param">
<li>
<span class='name'>value</span>
<span class='type'>(<tt>Object</tt>)</span>
<em class="default">(defaults to: <tt>NULL</tt>)</em>
—
<div class='inline'><p>the initial value</p>
</div>
</li>
<li>
<span class='name'>opts</span>
<span class='type'>(<tt><span class='object_link'><a href="Hash.html" title="Concurrent::Hash (class)">Hash</a></span></tt>)</span>
<em class="default">(defaults to: <tt>{}</tt>)</em>
—
<div class='inline'><p>the options to create a message with</p>
</div>
</li>
</ul>
<p class="tag_title">Options Hash (<tt>opts</tt>):</p>
<ul class="option">
<li>
<span class="name">:dup_on_deref</span>
<span class="type">(<tt>String</tt>)</span>
<span class="default">
— default:
<tt>false</tt>
</span>
— <div class='inline'><p>call <code>#dup</code> before returning
the data</p>
</div>
</li>
<li>
<span class="name">:freeze_on_deref</span>
<span class="type">(<tt>String</tt>)</span>
<span class="default">
— default:
<tt>false</tt>
</span>
— <div class='inline'><p>call <code>#freeze</code> before
returning the data</p>
</div>
</li>
<li>
<span class="name">:copy_on_deref</span>
<span class="type">(<tt>String</tt>)</span>
<span class="default">
— default:
<tt>nil</tt>
</span>
— <div class='inline'><p>call the given <code>Proc</code> passing
the internal value and returning the value returned from the proc</p>
</div>
</li>
</ul>
</div><table class="source_code">
<tr>
<td>
<pre class="lines">
61
62
63
64
65
66
67</pre>
</td>
<td>
<pre class="code"><span class="info file"># File 'lib/concurrent/ivar.rb', line 61</span>
<span class='kw'>def</span> <span class='id identifier rubyid_initialize'>initialize</span><span class='lparen'>(</span><span class='id identifier rubyid_value'>value</span> <span class='op'>=</span> <span class='const'>NULL</span><span class='comma'>,</span> <span class='id identifier rubyid_opts'>opts</span> <span class='op'>=</span> <span class='lbrace'>{</span><span class='rbrace'>}</span><span class='comma'>,</span> <span class='op'>&</span><span class='id identifier rubyid_block'>block</span><span class='rparen'>)</span>
<span class='kw'>if</span> <span class='id identifier rubyid_value'>value</span> <span class='op'>!=</span> <span class='const'>NULL</span> <span class='op'>&&</span> <span class='id identifier rubyid_block_given?'>block_given?</span>
<span class='id identifier rubyid_raise'>raise</span> <span class='const'>ArgumentError</span><span class='period'>.</span><span class='id identifier rubyid_new'>new</span><span class='lparen'>(</span><span class='tstring'><span class='tstring_beg'>'</span><span class='tstring_content'>provide only a value or a block</span><span class='tstring_end'>'</span></span><span class='rparen'>)</span>
<span class='kw'>end</span>
<span class='kw'>super</span><span class='lparen'>(</span><span class='op'>&</span><span class='kw'>nil</span><span class='rparen'>)</span>
<span class='id identifier rubyid_synchronize'>synchronize</span> <span class='lbrace'>{</span> <span class='id identifier rubyid_ns_initialize'>ns_initialize</span><span class='lparen'>(</span><span class='id identifier rubyid_value'>value</span><span class='comma'>,</span> <span class='id identifier rubyid_opts'>opts</span><span class='comma'>,</span> <span class='op'>&</span><span class='id identifier rubyid_block'>block</span><span class='rparen'>)</span> <span class='rbrace'>}</span>
<span class='kw'>end</span></pre>
</td>
</tr>
</table>
</div>
</div>
<div id="instance_method_details" class="method_details_list">
<h2>Instance Method Details</h2>
<div class="method_details first">
<h3 class="signature first" id="add_observer-instance_method">
#<strong>add_observer</strong>(observer = nil, func = :update, &block) ⇒ <tt>undocumented</tt>
</h3><div class="docstring">
<div class="discussion">
<p>Add an observer on this object that will receive notification on update.</p>
<p>Upon completion the <code>IVar</code> will notify all observers in a thread-safe way.
The <code>func</code> method of the observer will be called with three arguments: the
<code>Time</code> at which the <code>Future</code> completed the asynchronous operation, the
final <code>value</code> (or <code>nil</code> on rejection), and the final <code>reason</code> (or <code>nil</code> on
fulfillment).</p>
</div>
</div>
<div class="tags">
<p class="tag_title">Parameters:</p>
<ul class="param">
<li>
<span class='name'>observer</span>
<span class='type'>(<tt>Object</tt>)</span>
<em class="default">(defaults to: <tt>nil</tt>)</em>
—
<div class='inline'><p>the object that will be notified of changes</p>
</div>
</li>
<li>
<span class='name'>func</span>
<span class='type'>(<tt>Symbol</tt>)</span>
<em class="default">(defaults to: <tt>:update</tt>)</em>
—
<div class='inline'><p>symbol naming the method to call when this
<code>Observable</code> has changes`</p>
</div>
</li>
</ul>