blocks|key|2968053|text|在rails中，您只需执行以下操作：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2968054|clazz+=+'ExampleClass'.constantize|code-block|syntax|javascript|2968055|在纯红宝石中：|2968056|clazz+=+Object.const_get('ExampleClass')|2968057|使用模块：|2968058|module+Foo
++class+Bar
++end
end|2968059|您将使用|2968060|>+clazz+=+'Foo::Bar'.split('::').inject(Object)+{%7Co,c%7C+o.const_get+c}
++=>+Foo::Bar+
>+clazz.new
++=>+#<Foo::Bar:0x0000010110a4f8>+|2968061|entityMap^0|0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|U|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|V|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|W|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|X|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|Y|8|@]|9|@]|A|$]]|$1|M|3|N|5|D|7|Z|8|@]|9|@]|A|$E|F]]|$1|O|3|P|5|6|7|10|8|@]|9|@]|A|$]]|$1|Q|3|R|5|D|7|11|8|@]|9|@]|A|$E|F]]|$1|S|3|-4|5|6|7|12|8|@]|9|@]|A|$]]]|T|$]]

In rails you can just do:

<pre><code>clazz = 'ExampleClass'.constantize
</code></pre>

In pure ruby:

<pre><code>clazz = Object.const_get('ExampleClass')
</code></pre>

with modules:

<pre><code>module Foo
 class Bar
 end
end
</code></pre>

you would use

<pre><code>&gt; clazz = 'Foo::Bar'.split('::').inject(Object) {|o,c| o.const_get c}
 =&gt; Foo::Bar 
&gt; clazz.new
 =&gt; #&lt;Foo::Bar:0x0000010110a4f8&gt; 
</code></pre>

blocks|key|267404|text|在Rails中非常简单:使用String#constantize|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|267405|class_name+=+"MyClass"
instance+=+class_name.constantize.new|code-block|syntax|javascript|267406|entityMap|0|LINK|mutability|MUTABLE|url|http://api.rubyonrails.org/classes/String.html#method-i-constantize^0|E|I|E|I|0|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@$9|T|A|U|B|C]]|D|@$9|V|A|W|1|X]]|E|$]]|$1|F|3|G|5|H|7|Y|8|@]|D|@]|E|$I|J]]|$1|K|3|-4|5|6|7|Z|8|@]|D|@]|E|$]]]|L|$M|$5|N|O|P|E|$Q|R]]]]

Very simple in Rails: use <a href="http://api.rubyonrails.org/classes/String.html#method-i-constantize" rel="noreferrer"><code>String#constantize</code></a>

<pre><code>class_name = "MyClass"
instance = class_name.constantize.new
</code></pre>

blocks|key|3181898|text|试试这个：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3181899|Kernel.const_get("MyClass").new|code-block|syntax|javascript|3181900|然后循环遍历对象的实例变量：|3181901|obj.instance_variables.each+do+%7Cv%7C
++#+do+something
end|3181902|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|N|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|O|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

Try this:

<pre><code>Kernel.const_get("MyClass").new
</code></pre>

Then to loop through an object's instance variables: 

<pre><code>obj.instance_variables.each do |v|
 # do something
end
</code></pre>

blocks|key|2968123|text|module+One
++module+Two
++++class+Three
++++++def+say_hi
++++++++puts+"say+hi"
++++++end
++++end
++end
end

one+=+Object.const_get+"One"

puts+one.class+#+=>+Module

three+=+One::Two.const_get+"Three"

puts+three.class+#+=>+Class

three.new.say_hi+#+=>+"say+hi"|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|2968124|在Ruby2.0和更早的版本中，Object.const_get将在像Foo::Bar这样的命名空间上进行recursively+perform+a+lookup。上面的示例是提前知道名称空间的，并强调了可以在模块上直接调用const_get的事实，而不是在Object上独占调用。|unstyled|offset|length|style|CODE|2968125|entityMap|0|LINK|mutability|MUTABLE|url|http://ruby-doc.org/core-2.0.0/Module.html#method-i-const_get^0|0|G|G|Z|8|34|9|3L|6|1H|S|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@]|A|$B|C]]|$1|D|3|E|5|F|7|T|8|@$G|U|H|V|I|J]|$G|W|H|X|I|J]|$G|Y|H|Z|I|J]|$G|10|H|11|I|J]]|9|@$G|12|H|13|1|14]]|A|$]]|$1|K|3|-4|5|F|7|15|8|@]|9|@]|A|$]]]|L|$M|$5|N|O|P|A|$Q|R]]]]

<pre><code>module One
 module Two
 class Three
 def say_hi
 puts "say hi"
 end
 end
 end
end

one = Object.const_get "One"

puts one.class # =&gt; Module

three = One::Two.const_get "Three"

puts three.class # =&gt; Class

three.new.say_hi # =&gt; "say hi"
</code></pre>

In ruby 2.0 and, possibly earlier releases, <code>Object.const_get</code> will <a href="http://ruby-doc.org/core-2.0.0/Module.html#method-i-const_get" rel="noreferrer">recursively perform a lookup</a> on a namespaces like <code>Foo::Bar</code>. The example above is when the namespace is known ahead of time and highlights the fact that <code>const_get</code> can be called on modules directly as opposed to exclusively on <code>Object</code>.

I have the name of a class and I want to create an instance of that class so that I can loop through each rails attribute that is present in the schema of that class.

How would I go about doing that?

<ol>
<li>I have the name as a string of the class I want to check</li>
<li>I guess I need to instantiate a class instance so that I can</li>
<li>Loop through it's attributes and print them.</li>
</ol>

How do I create a class instance from a string name in ruby?

Kernel

我有一个类的名称，我想创建该类的一个实例，这样我就可以遍历该类的模式中存在的每个rails属性。我该怎么做呢？我有一个字符串形式的类名我想要检查我猜我需要实例化一个类实例，这样我就可以循环遍历它的属性并打印它们。

问如何从ruby中的字符串名创建类实例？
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