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<h3>Parent</h3>
<p class="link"><a href="Object.html">Object</a>
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<!-- Method Quickref -->
<div id="method-list-section" class="nav-section">
<h3>Methods</h3>
<ul class="link-list" role="directory">
<li ><a href="#method-i-eval">#eval</a>
<li ><a href="#method-i-irb">#irb</a>
<li ><a href="#method-i-local_variable_defined-3F">#local_variable_defined?</a>
<li ><a href="#method-i-local_variable_get">#local_variable_get</a>
<li ><a href="#method-i-local_variable_set">#local_variable_set</a>
<li ><a href="#method-i-local_variables">#local_variables</a>
<li ><a href="#method-i-receiver">#receiver</a>
<li ><a href="#method-i-source_location">#source_location</a>
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<main role="main" aria-labelledby="class-Binding">
<h1 id="class-Binding" class="class">
class Binding
</h1>
<section class="description">
<p>Objects of class <a href="Binding.html"><code>Binding</code></a> encapsulate the execution context at some particular place in the code and retain this context for future use. The variables, methods, value of <code>self</code>, and possibly an iterator block that can be accessed in this context are all retained. <a href="Binding.html"><code>Binding</code></a> objects can be created using <a href="Kernel.html#method-i-binding"><code>Kernel#binding</code></a>, and are made available to the callback of <a href="Kernel.html#method-i-set_trace_func"><code>Kernel#set_trace_func</code></a> and instances of <a href="TracePoint.html"><code>TracePoint</code></a>.</p>
<p>These binding objects can be passed as the second argument of the <a href="Kernel.html#method-i-eval"><code>Kernel#eval</code></a> method, establishing an environment for the evaluation.</p>
<pre class="ruby"><span class="ruby-keyword">class</span> <span class="ruby-constant">Demo</span>
<span class="ruby-keyword">def</span> <span class="ruby-identifier ruby-title">initialize</span>(<span class="ruby-identifier">n</span>)
<span class="ruby-ivar">@secret</span> = <span class="ruby-identifier">n</span>
<span class="ruby-keyword">end</span>
<span class="ruby-keyword">def</span> <span class="ruby-identifier ruby-title">get_binding</span>
<span class="ruby-identifier">binding</span>
<span class="ruby-keyword">end</span>
<span class="ruby-keyword">end</span>
<span class="ruby-identifier">k1</span> = <span class="ruby-constant">Demo</span>.<span class="ruby-identifier">new</span>(<span class="ruby-value">99</span>)
<span class="ruby-identifier">b1</span> = <span class="ruby-identifier">k1</span>.<span class="ruby-identifier">get_binding</span>
<span class="ruby-identifier">k2</span> = <span class="ruby-constant">Demo</span>.<span class="ruby-identifier">new</span>(<span class="ruby-value">-3</span>)
<span class="ruby-identifier">b2</span> = <span class="ruby-identifier">k2</span>.<span class="ruby-identifier">get_binding</span>
<span class="ruby-identifier">eval</span>(<span class="ruby-string">"@secret"</span>, <span class="ruby-identifier">b1</span>) <span class="ruby-comment">#=> 99</span>
<span class="ruby-identifier">eval</span>(<span class="ruby-string">"@secret"</span>, <span class="ruby-identifier">b2</span>) <span class="ruby-comment">#=> -3</span>
<span class="ruby-identifier">eval</span>(<span class="ruby-string">"@secret"</span>) <span class="ruby-comment">#=> nil</span>
</pre>
<p><a href="Binding.html"><code>Binding</code></a> objects have no class-specific methods.</p>
</section>
<section id="5Buntitled-5D" class="documentation-section">
<section id="public-instance-5Buntitled-5D-method-details" class="method-section">
<header>
<h3>Public Instance Methods</h3>
</header>
<div id="method-i-eval" class="method-detail ">
<div class="method-heading">
<span class="method-callseq">
eval(string [, filename [,lineno]]) → obj
</span>
<span class="method-click-advice">click to toggle source</span>
</div>
<div class="method-description">
<p>Evaluates the Ruby expression(s) in <em>string</em>, in the <em>binding</em>'s context. If the optional <em>filename</em> and <em>lineno</em> parameters are present, they will be used when reporting syntax errors.</p>
<pre class="ruby"><span class="ruby-keyword">def</span> <span class="ruby-identifier ruby-title">get_binding</span>(<span class="ruby-identifier">param</span>)
<span class="ruby-identifier">binding</span>
<span class="ruby-keyword">end</span>
<span class="ruby-identifier">b</span> = <span class="ruby-identifier">get_binding</span>(<span class="ruby-string">"hello"</span>)
<span class="ruby-identifier">b</span>.<span class="ruby-identifier">eval</span>(<span class="ruby-string">"param"</span>) <span class="ruby-comment">#=> "hello"</span>
</pre>
<div class="method-source-code" id="eval-source">
<pre>static VALUE
bind_eval(int argc, VALUE *argv, VALUE bindval)
{
VALUE args[4];
rb_scan_args(argc, argv, "12", &args[0], &args[2], &args[3]);
args[1] = bindval;
return rb_f_eval(argc+1, args, Qnil /* self will be searched in eval */);
}</pre>
</div>
</div>
</div>
<div id="method-i-irb" class="method-detail ">
<div class="method-heading">
<span class="method-name">irb</span><span
class="method-args">()</span>
<span class="method-click-advice">click to toggle source</span>
</div>
<div class="method-description">
<p>Opens an IRB session where <code>binding.irb</code> is called which allows for interactive debugging. You can call any methods or variables available in the current scope, and mutate state if you need to.</p>
<p>Given a Ruby file called <code>potato.rb</code> containing the following code:</p>
<pre class="ruby"><span class="ruby-keyword">class</span> <span class="ruby-constant">Potato</span>
<span class="ruby-keyword">def</span> <span class="ruby-identifier ruby-title">initialize</span>
<span class="ruby-ivar">@cooked</span> = <span class="ruby-keyword">false</span>
<span class="ruby-identifier">binding</span>.<span class="ruby-identifier">irb</span>
<span class="ruby-identifier">puts</span> <span class="ruby-node">"Cooked potato: #{@cooked}"</span>
<span class="ruby-keyword">end</span>
<span class="ruby-keyword">end</span>
<span class="ruby-constant">Potato</span>.<span class="ruby-identifier">new</span>
</pre>
<p>Running <code>ruby potato.rb</code> will open an IRB session where <code>binding.irb</code> is called, and you will see the following:</p>
<pre>$ ruby potato.rb
From: potato.rb @ line 4 :
1: class Potato
2: def initialize
3: @cooked = false
=> 4: binding.irb
5: puts "Cooked potato: #{@cooked}"
6: end
7: end
8:
9: Potato.new
irb(#<Potato:0x00007feea1916670>):001:0></pre>
<p>You can type any valid Ruby code and it will be evaluated in the current context. This allows you to debug without having to run your code repeatedly:</p>
<pre>irb(#<Potato:0x00007feea1916670>):001:0> @cooked
=> false
irb(#<Potato:0x00007feea1916670>):002:0> self.class
=> Potato
irb(#<Potato:0x00007feea1916670>):003:0> caller.first
=> ".../2.5.1/lib/ruby/2.5.0/irb/workspace.rb:85:in `eval'"
irb(#<Potato:0x00007feea1916670>):004:0> @cooked = true
=> true</pre>
<p>You can exit the IRB session with the <code>exit</code> command. Note that exiting will resume execution where <code>binding.irb</code> had paused it, as you can see from the output printed to standard output in this example:</p>
<pre>irb(#<Potato:0x00007feea1916670>):005:0> exit
Cooked potato: true</pre>
<p>See IRB for more information.</p>
<div class="method-source-code" id="irb-source">
<pre><span class="ruby-comment"># File lib/irb.rb, line 901</span>
<span class="ruby-keyword">def</span> <span class="ruby-identifier ruby-title">irb</span>
<span class="ruby-constant">IRB</span>.<span class="ruby-identifier">setup</span>(<span class="ruby-identifier">source_location</span>[<span class="ruby-value">0</span>], <span class="ruby-value">argv:</span> [])
<span class="ruby-identifier">workspace</span> = <span class="ruby-constant">IRB</span><span class="ruby-operator">::</span><span class="ruby-constant">WorkSpace</span>.<span class="ruby-identifier">new</span>(<span class="ruby-keyword">self</span>)
<span class="ruby-constant">STDOUT</span>.<span class="ruby-identifier">print</span>(<span class="ruby-identifier">workspace</span>.<span class="ruby-identifier">code_around_binding</span>)
<span class="ruby-identifier">binding_irb</span> = <span class="ruby-constant">IRB</span><span class="ruby-operator">::</span><span class="ruby-constant">Irb</span>.<span class="ruby-identifier">new</span>(<span class="ruby-identifier">workspace</span>)
<span class="ruby-identifier">binding_irb</span>.<span class="ruby-identifier">context</span>.<span class="ruby-identifier">irb_path</span> = <span class="ruby-constant">File</span>.<span class="ruby-identifier">expand_path</span>(<span class="ruby-identifier">source_location</span>[<span class="ruby-value">0</span>])
<span class="ruby-identifier">binding_irb</span>.<span class="ruby-identifier">run</span>(<span class="ruby-constant">IRB</span>.<span class="ruby-identifier">conf</span>)
<span class="ruby-keyword">end</span></pre>
</div>
</div>
</div>
<div id="method-i-local_variable_defined-3F" class="method-detail ">
<div class="method-heading">
<span class="method-callseq">
local_variable_defined?(symbol) → obj
</span>
<span class="method-click-advice">click to toggle source</span>
</div>
<div class="method-description">
<p>Returns <code>true</code> if a local variable <code>symbol</code> exists.</p>
<pre class="ruby"><span class="ruby-keyword">def</span> <span class="ruby-identifier ruby-title">foo</span>
<span class="ruby-identifier">a</span> = <span class="ruby-value">1</span>
<span class="ruby-identifier">binding</span>.<span class="ruby-identifier">local_variable_defined?</span>(<span class="ruby-value">:a</span>) <span class="ruby-comment">#=> true</span>
<span class="ruby-identifier">binding</span>.<span class="ruby-identifier">local_variable_defined?</span>(<span class="ruby-value">:b</span>) <span class="ruby-comment">#=> false</span>
<span class="ruby-keyword">end</span>
</pre>
<p>This method is the short version of the following code:</p>
<pre class="ruby"><span class="ruby-identifier">binding</span>.<span class="ruby-identifier">eval</span>(<span class="ruby-node">"defined?(#{symbol}) == 'local-variable'"</span>)
</pre>
<div class="method-source-code" id="local_variable_defined-3F-source">
<pre>static VALUE
bind_local_variable_defined_p(VALUE bindval, VALUE sym)
{
ID lid = check_local_id(bindval, &sym);
const rb_binding_t *bind;
const rb_env_t *env;
if (!lid) return Qfalse;
GetBindingPtr(bindval, bind);
env = VM_ENV_ENVVAL_PTR(vm_block_ep(&bind->block));
return get_local_variable_ptr(&env, lid) ? Qtrue : Qfalse;
}</pre>
</div>
</div>
</div>
<div id="method-i-local_variable_get" class="method-detail ">
<div class="method-heading">
<span class="method-callseq">
local_variable_get(symbol) → obj
</span>
<span class="method-click-advice">click to toggle source</span>
</div>
<div class="method-description">
<p>Returns the value of the local variable <code>symbol</code>.</p>
<pre class="ruby"><span class="ruby-keyword">def</span> <span class="ruby-identifier ruby-title">foo</span>
<span class="ruby-identifier">a</span> = <span class="ruby-value">1</span>
<span class="ruby-identifier">binding</span>.<span class="ruby-identifier">local_variable_get</span>(<span class="ruby-value">:a</span>) <span class="ruby-comment">#=> 1</span>
<span class="ruby-identifier">binding</span>.<span class="ruby-identifier">local_variable_get</span>(<span class="ruby-value">:b</span>) <span class="ruby-comment">#=> NameError</span>
<span class="ruby-keyword">end</span>
</pre>
<p>This method is the short version of the following code:</p>
<pre class="ruby"><span class="ruby-identifier">binding</span>.<span class="ruby-identifier">eval</span>(<span class="ruby-node">"#{symbol}"</span>)
</pre>
<div class="method-source-code" id="local_variable_get-source">
<pre>static VALUE
bind_local_variable_get(VALUE bindval, VALUE sym)
{
ID lid = check_local_id(bindval, &sym);
const rb_binding_t *bind;
const VALUE *ptr;
const rb_env_t *env;
if (!lid) goto undefined;
GetBindingPtr(bindval, bind);
env = VM_ENV_ENVVAL_PTR(vm_block_ep(&bind->block));
if ((ptr = get_local_variable_ptr(&env, lid)) == NULL) {
sym = ID2SYM(lid);
undefined:
rb_name_err_raise("local variable `%1$s' is not defined for %2$s",
bindval, sym);
}
return *ptr;
}</pre>
</div>
</div>
</div>
<div id="method-i-local_variable_set" class="method-detail ">
<div class="method-heading">
<span class="method-callseq">
local_variable_set(symbol, obj) → obj
</span>
<span class="method-click-advice">click to toggle source</span>
</div>
<div class="method-description">
<p><a href="Set.html"><code>Set</code></a> local variable named <code>symbol</code> as <code>obj</code>.</p>
<pre class="ruby"><span class="ruby-keyword">def</span> <span class="ruby-identifier ruby-title">foo</span>
<span class="ruby-identifier">a</span> = <span class="ruby-value">1</span>
<span class="ruby-identifier">bind</span> = <span class="ruby-identifier">binding</span>
<span class="ruby-identifier">bind</span>.<span class="ruby-identifier">local_variable_set</span>(<span class="ruby-value">:a</span>, <span class="ruby-value">2</span>) <span class="ruby-comment"># set existing local variable `a'</span>
<span class="ruby-identifier">bind</span>.<span class="ruby-identifier">local_variable_set</span>(<span class="ruby-value">:b</span>, <span class="ruby-value">3</span>) <span class="ruby-comment"># create new local variable `b'</span>
<span class="ruby-comment"># `b' exists only in binding</span>
<span class="ruby-identifier">p</span> <span class="ruby-identifier">bind</span>.<span class="ruby-identifier">local_variable_get</span>(<span class="ruby-value">:a</span>) <span class="ruby-comment">#=> 2</span>
<span class="ruby-identifier">p</span> <span class="ruby-identifier">bind</span>.<span class="ruby-identifier">local_variable_get</span>(<span class="ruby-value">:b</span>) <span class="ruby-comment">#=> 3</span>
<span class="ruby-identifier">p</span> <span class="ruby-identifier">a</span> <span class="ruby-comment">#=> 2</span>
<span class="ruby-identifier">p</span> <span class="ruby-identifier">b</span> <span class="ruby-comment">#=> NameError</span>
<span class="ruby-keyword">end</span>
</pre>
<p>This method behaves similarly to the following code:</p>
<pre class="ruby"><span class="ruby-identifier">binding</span>.<span class="ruby-identifier">eval</span>(<span class="ruby-node">"#{symbol} = #{obj}"</span>)
</pre>
<p>if <code>obj</code> can be dumped in Ruby code.</p>
<div class="method-source-code" id="local_variable_set-source">
<pre>static VALUE
bind_local_variable_set(VALUE bindval, VALUE sym, VALUE val)
{
ID lid = check_local_id(bindval, &sym);
rb_binding_t *bind;
const VALUE *ptr;
const rb_env_t *env;
if (!lid) lid = rb_intern_str(sym);
GetBindingPtr(bindval, bind);
env = VM_ENV_ENVVAL_PTR(vm_block_ep(&bind->block));
if ((ptr = get_local_variable_ptr(&env, lid)) == NULL) {
/* not found. create new env */
ptr = rb_binding_add_dynavars(bindval, bind, 1, &lid);
env = VM_ENV_ENVVAL_PTR(vm_block_ep(&bind->block));
}
RB_OBJ_WRITE(env, ptr, val);
return val;
}</pre>
</div>
</div>
</div>
<div id="method-i-local_variables" class="method-detail ">
<div class="method-heading">
<span class="method-callseq">
local_variables → Array
</span>
<span class="method-click-advice">click to toggle source</span>
</div>
<div class="method-description">
<p>Returns the names of the binding's local variables as symbols.</p>
<pre class="ruby"><span class="ruby-keyword">def</span> <span class="ruby-identifier ruby-title">foo</span>
<span class="ruby-identifier">a</span> = <span class="ruby-value">1</span>
<span class="ruby-value">2</span>.<span class="ruby-identifier">times</span> <span class="ruby-keyword">do</span> <span class="ruby-operator">|</span><span class="ruby-identifier">n</span><span class="ruby-operator">|</span>
<span class="ruby-identifier">binding</span>.<span class="ruby-identifier">local_variables</span> <span class="ruby-comment">#=> [:a, :n]</span>
<span class="ruby-keyword">end</span>
<span class="ruby-keyword">end</span>
</pre>
<p>This method is the short version of the following code:</p>
<pre class="ruby"><span class="ruby-identifier">binding</span>.<span class="ruby-identifier">eval</span>(<span class="ruby-string">"local_variables"</span>)
</pre>
<div class="method-source-code" id="local_variables-source">
<pre>static VALUE
bind_local_variables(VALUE bindval)
{
const rb_binding_t *bind;
const rb_env_t *env;
GetBindingPtr(bindval, bind);
env = VM_ENV_ENVVAL_PTR(vm_block_ep(&bind->block));
return rb_vm_env_local_variables(env);
}</pre>
</div>
</div>
</div>
<div id="method-i-receiver" class="method-detail ">
<div class="method-heading">
<span class="method-callseq">
receiver → object
</span>
<span class="method-click-advice">click to toggle source</span>
</div>
<div class="method-description">
<p>Returns the bound receiver of the binding object.</p>
<div class="method-source-code" id="receiver-source">
<pre>static VALUE
bind_receiver(VALUE bindval)
{
const rb_binding_t *bind;
GetBindingPtr(bindval, bind);
return vm_block_self(&bind->block);
}</pre>
</div>
</div>
</div>
<div id="method-i-source_location" class="method-detail ">
<div class="method-heading">
<span class="method-callseq">
source_location → [String, Integer]
</span>
<span class="method-click-advice">click to toggle source</span>
</div>
<div class="method-description">
<p>Returns the Ruby source filename and line number of the binding object.</p>
<div class="method-source-code" id="source_location-source">
<pre>static VALUE
bind_location(VALUE bindval)
{
VALUE loc[2];
const rb_binding_t *bind;
GetBindingPtr(bindval, bind);
loc[0] = pathobj_path(bind->pathobj);
loc[1] = INT2FIX(bind->first_lineno);
return rb_ary_new4(2, loc);
}</pre>
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