Table of contents

Introduction

Solution

Example

Frequently Asked Questions

4.1.

What is the cycle of a bug?

4.2.

What are a bug report's essential components?

4.3.

What do Ruby exceptions mean?

4.4.

What distinguishes raise/rescue from throw/catch?

4.5.

What are Ruby methods' three levels of access control called?

Conclusion

Last Updated: Mar 27, 2024

Fixing Bugs in Someone Else’s Class

Author Mayank Goyal

Introduction

Imagine that you are utilizing a class with a problem in one of its methods. You are aware of the problem and how to resolve it, but you are unable or unwilling to alter the source code.

Solution

From within your program, extend the class and replace the problematic method with a workaround. To still access the flawed version of the technique, create an alias for it.

Suppose we’re trying to use the buggy method in the rexa class defined here:

class rexa
 def function(pleasure)
 return pleasure * 3 # FIXME: Actually triples your pleasure.
 end
end

m = rexa.new
m.function(6) # => 18
Reopen the class, alias the buggy method to another name, and then redefine it with a
correct implementation:
class rexa
 alias :function_BUGGY :function
 def function(pleasure)
 return pleasure * 2
 end
end
m.function(6) # => 12
m.function_BUGGY(6) # => 18

A class, function, or method cannot be changed after it has been defined in many programming languages. This action is permissible but discouraged in other languages.

The ability to change classes on the fly is another tool in the arsenal for Ruby programmers to employ as needed. Although adding new code to a class is its most frequent usage, it can also be used to deploy a drop-in replacement for a method's sluggish or defective implementation.

Since Ruby is a purely interpreted language, we should be able to find the source code of any Ruby class used by our program. If a method in one of the classes has a bug, we should be able to copy and paste the original Ruby implementation into our code and fix the bug in the new copy. It's not an efficient technique, but it’s better than distributing a slightly modified version of the entire class or library (that is, copying and pasting a whole file).

You should report your corrections to the software's maintainer in addition to fixing the problematic behavior. The sooner the fix is implemented in your code, the better. You should at least publish the fix online so that others can find it if the software package has been abandoned.

Instead of redefining an existing method if it isn't broken but doesn't do what you want it to, add a new method to the class (or make a subclass). The behavior of the technique may be used by methods you are unaware of.

Of course, there might be techniques that rely on a technique's poor behavior, but that's less likely.

Example

Ruby will typically attempt to call the specified method if it comes across an identifier that does not refer to a defined local variable. Ruby, however, considers address = an as a local variable initialization when it comes across it in the initialize method and fails to call the setter. This happens when Ruby comes across an identifier on the left side of an assignment operator that starts with a lowercase character or an underscore. The answer is to add the self keyword before the address to indicate that we wish to call the writer method. The initializing procedure is seen below in replication:

def initialize(a)
  self.address = a
end

Alternatively, we could also fix the bug by directly assigning the value to the instance variable within the initialize method like so:

def initialize(a)
  @address = clean(a)
end

Frequently Asked Questions

What is the cycle of a bug?

A defect's voyage through a defect cycle, commonly referred to as a bug life cycle, occurs throughout the defect's existence. As the bug is governed by the software testing process and dependent on the tools employed, it differs in organizations and from project to project.

What are a bug report's essential components?

A good bug report should be dense with information, clear and simple, and contain only one bug. It should provide user instructions and environment information that the developer can utilize to replicate the error on his end. Developers are effectively wandering in the dark without the ability to duplicate the error.

What do Ruby exceptions mean?

An instance of a class Exception or a descendant thereof is a Ruby exception. The Ruby programming language displays unusual behavior when something goes wrong. By default, Ruby programs end when an exception is thrown.

What distinguishes raise/rescue from throw/catch?

Throw and catch are control-flow structures that take matching symbols as inputs and raise and rescue to raise and handle exceptions. Throwing and catching are less frequently used than managing exceptions with raise and rescue.

What are Ruby methods' three levels of access control called?

Methods in Ruby can be either public, protected, or private.

Public methods can be invoked in any scope and do not impose access controls.

Only the class and subclasses that define a protected method can access it.

Private methods are only accessible and viewable within the class that defines them. We can only access them within the context of the current object.