Magic 20 events

Class: RuboCop::Cop::Style::FrozenStringLiteralComment RuboCop master

Could you create a list of the files with problems and add them to this issue? This will be a huge help for us to narrow down the areas that need more specific changes. # and forces projects to use frozen string literals.

This mode is “experimental” and has not been discussed thoroughly. This will be revisited before Ruby 3.1 to either allow `copy` or to instead remove this mode. It must appear in the first comment section of a file.

ruby frozen string literal

As a result, many premature, inscrutable programming decisions have been made in performance’s name. Didn’t we just append to an immutable object? Even worse, this magic comment is frequently misunderstood. This particular magic comment, however, has a unique history.

What are Strings (and String Literals)?

Since the 2.3.0 release of Ruby, there’s been the optional feature to make all string literals frozen. This means that any string literal within your code is frozen and cannot be modified. First, it’s important to note that this change is just the first step towards all string literals becoming immutable in Ruby 3. String literals are simply strings that are created using Ruby’s built-in string syntax. This includes those created using double quotes (“), single quotes (‘), or the special forms %Q and %q.

It makes the code uglier and needs to be called everywhere you declare a String. You are commenting using your account. The deploy was done after hours one evening and I was ready to witness the magic. I have been working on a project over the past year for a client with a large Ruby on Rails application.

Gems with Frozen-String-Literal Friendly Pull Requests

Frozen_string_literal reduces the generated garbage by ~100MB or ~20%! Free performance by adding a one line comment. I am still exploring when to use the magic comment and when it shouldn’t be used. If you are using this throughout your applications it might be worth measuring with and without their use.

Blocks are a handy and powerful feature in Ruby, and we can use them anywhere. Blocks are anonymous pieces of code that accept input from arguments and return a value. I believe that performance can be an ‘Appeal to Common Belief’ fallacy. The winds are against you anytime you argue against it.

Today I checked one of the solutions made by our Junior Rails Developer classstudent. As part of the course they make Rails apps but also learn from smaller code 5 Using Python on a Mac Python 3 10.7 documentation examples delivered by It appears that the guidance in this area may have changed, as StyleCop now enforces the use of the C# specific aliases.

  • This mode is “experimental” and has not been discussed thoroughly.
  • Just add this comment in the first line of your files.
  • Open a production Ruby file, and you’ll often see this magic comment at the top.
  • Allocating just a single object for both ‘a’ and ‘b’ reduces the amount of memory used and this, in turn, reduces pressure on the garbage collector.
  • By calling the freeze method inside the constructor, it’s possible to guarantee that an object will never change.

If you’re preparing for the upcoming Ruby 2.3 release, you’re in the right place. Let’s take a look at what this all means, and how it will affect every day programming in Ruby. As it goes with most updates, there will be some short term pain as Ruby changes to make string literals immutable by default.

Positive Strings

Since the router is used for every web page request, it needs to be fast. That means a lot of frozen string literals. While comments are typically ignored by Ruby, special “magic Information Security Analysts : Occupational Outlook Handbook: : U S Bureau of Labor Statistics comments” contain directives that affect how the code is interpreted. Top-level magic comments must start on the first line, or on the second line if the first line looks like #!

  • I added it to every Ruby file in the project and was included as part of the weekly deploy.
  • Frozen_string_literal one of easiest way to optimize Ruby application, but sometimes it raises error if your old code is not compatible.
  • Rb file or Gemfile, and the results will be output.
  • A common understanding of .freeze is that it makes the string immutable.
  • Some estimates put the saving of object allocation as high as 30 percent of all string literals.

Objects should never change after they’ve been initialized. Every get_key is called, it will allocate new copy of “my_key”, which is then immediately thrown away as garbage. It sounds like there is a benefit to use this feature but not everywhere, the exact result I saw in performance graphs. Response times drastically improved as you can see from the above graph. Mike includes some benchmarks that show improved memory footprint for Sidekiq. Gets called if no message is specified when calling add_offense or add_global_offense Cops are discouraged to override this; instead pass your message directly.

Instance Method Summary

A “string literal” is a sequence of characters from the source character set enclosed in double quotation marks (” “). String literals are used to represent a sequence of characters which, taken together, form a null-terminated string. There is no way to unfreeze a frozen object. The frozen state is stored within the object. Calling freeze sets the frozen state and thereby prevents further modification. This includes modifications to the object’s frozen state.

  • Frozen_string_literal reduces the generated garbage by ~100MB or ~20%!
  • That’s still a problem you have to deal with but it’s better than unexpected inconsistencies in your data.
  • Could you create a list of the files with problems and add them to this issue?

The good news is that it will happen gradually, and it won’t be difficult to detect and fix existing code that’s affected by this change. In return, we’re going to get a version of Ruby that uses less memory and thus runs a bit quicker. Given the low overhead of having to call ‘dup’ when we want an unfrozen string, this is certainly a tradeoff worth making. The freeze method in Ruby is used to ensure that an object cannot be modified. This method is a great way to create immutable objects. Any attempt to modify an object that has called the freeze method will result in the program throwing a runtime error.

Ruby has freeze method to minimize string allocation and treat it as immutable. The threads title, Reconsider impact of frozen_string_literal on dynamic strings, I found interesting. Maybe this is a clue and dynamic strings being frozen in my application is part of the problem.

Ruby 2.1: Profiling Ruby

I thought about the use of the magic comment and decided to give it a try. I added it to every Ruby file in the project and was included as part of the weekly deploy. Frozen string literals reduce object allocations because Ruby doesn’t allocate the same content in a new string object each time the literal is encountered. In Ruby, whenever you have a statement defining a string as a literal, it’s a new object, with its own space in memory. “a” in one line of your code and “a” in another have the same contents, but are separate. And if those statements are called more than once, then every time they’re called, new strings are allocated in memory.

Any others have more information to share, please reach out. I noticed right away the response times of API calls were slower, not faster. Maybe I was seeing the effects of cold cache calls and things would improve overnight. Note that the cop will accept files where the comment exists but is set to false instead of true.

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