Ruby on Rails Q & A


What is the difference between a symbol and a string in Rails?

In Ruby, both symbols and strings seem to serve similar purposes, as they both represent text-based data. However, there are fundamental differences between the two that influence when and how they’re used:


  1. Immutability:

A symbol is immutable, meaning its value cannot be changed after it’s created. This is in contrast to a string, which can be modified. For example, you can append to a string with the `<<` method, but you can’t do that with a symbol.


  1. Object Identity:

Every time you reference a symbol, it points to the same object in memory. Conversely, creating a new string with the same value results in a new object in memory. This makes symbols efficient for repeated use, as they don’t lead to multiple duplicate objects in memory.


  1. Use Cases:

Symbols are often used as keys in hashes or to represent method names, especially when the identity of the object is more important than its content. Strings, on the other hand, are more versatile and are used when the content is of primary importance, like for textual data manipulation or storage.


  1. Performance:

Due to their immutability and unique object identity, symbols can offer better performance in specific scenarios. For instance, when used as keys in a hash, checking for equality (i.e., checking if a hash has a certain key) with symbols is faster than with strings.


  1. Conversion:

You can easily convert between symbols and strings using the `to_s` and `to_sym` methods. For instance, `:symbol.to_s` will convert the symbol `:symbol` to the string `”symbol”`, and `”string”.to_sym` will convert the string `”string”` to the symbol `:string`.


  1. Storage:

Symbols are not garbage collected until a program ends, meaning once a symbol is created, it stays in memory. This could lead to a memory leak if you dynamically create a large number of symbols. Strings don’t have this behavior and are garbage collected as needed.


While symbols and strings both represent text data in Ruby, their underlying behaviors and characteristics dictate different use cases. Knowing when to use which can help write more efficient and idiomatic Ruby code.

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Senior Software Engineer with a focus on remote work. Proficient in Ruby on Rails. Expertise spans y6ears in Ruby on Rails development, contributing to B2C financial solutions and data engineering.