Novel Eval

Novel Eval seems to have several descriptions in memos ... In order to manipulate words, images and expressions and to re-create themselves comfortably, most people come to hand Advanced biomedical technology that can not be inserted is necessary.

EVAL. In many interpreted languages ​​(Pyon, Ruby, JavaScript, etc.), there is an eval function that uses the language's grammar string and calls the language's interpreter for that string. With this language's evaluation tool you can use very powerful features with very little code. This is the Query language. Consistently applying appropriate validation or escaping to all code that interacts with the query API is a difficult and error-prone process, and implementing this feature will repeatedly increase the risk of vulnerability being injected. Use or develop an API to mediate application code and interfaces based on the original query language (SQL, LDAP, etc.), and publish a safer API. Avoid code to construct queries based on the binding of special strings and doubt unreliable data based on fixed query section

Define_method is used to dynamically define methods at run time. In Part 1 of the series you learned how to dynamically define methods using eval, class_eval, or instance eval. The main problem of defining methods using this method is that errors are prone to error because methods are defined using strings. A good time to use `define_method` to oppose the use of explicitly defined methods is that you have to create a set of methods that all have the same basic structure. Const_get is used to retrieve constants of the same name as strings or symbols passed as parameters to the `const_get` method. It can be used to load ruby ​​classes from strings. The method behind ActiveSupport 's constantize method. On the other hand, const_set can be used to create a new constant or update an existing constant.