This template provides a convenient way to work with Opt types in Nim. It allows you to execute a block of code (body) only when the Opt is not empty.

self is the Opt instance being checked. value is the variable name to be used within the body for the unwrapped value. body is a block of code that is executed only if self contains a value.

The value within body is automatically unwrapped from the Opt, making it simpler to work with without needing explicit checks or unwrapping.

Example:

let myOpt = Opt.some(5)
myOpt.withValue(value):
  echo value # Will print 5

Note: This is a template, and it will be inlined at the call site, offering good performance.