The Ruby idiom a ||= b is a common shorthand used in Ruby programming that serves as a conditional assignment operator. This idiom is used to assign the value of b to a if a is nil or false. Essentially, it is a concise way to write:
a = a || b
This means that if a is either nil or false, then a will be set to b. If a already has a truthy value (anything other than nil or false in Ruby), a will retain its original value.
How It Works
The ||= operator first evaluates the left-hand side (a). If this evaluation yields nil or false (the only two "falsy" values in Ruby), Ruby then evaluates the right-hand side (b) and sets a to this value. If a is anything other than nil or false, a remains unchanged.
Practical Example
Consider a scenario where you might want to set a default value for a variable if it hasn't already been set:
name ||= "Default Name"
Here, if name is nil or false, it will be set to "Default Name". If name already has a non-falsy value, it will remain as is.
Special Cases and Considerations
It's important to note that a ||= b is not exactly equivalent to a = a || b due to the way Ruby handles variable initialization and parsing. If a is not previously defined, a = a || b would raise an error because it tries to access an uninitialized variable a. However, a ||= b...
