How deeply does The Well-Grounded Rubyist, Fourth Edition cover callable?

Explains Proc creation, invocation syntax, closures, variable bindings, and method objects, while deferring exhaustive callable behavior.

Callable

As explained in The Well-Grounded Rubyist, Fourth Edition

A callable object is an object that provides a way to invoke encapsulated behavior as a function-like operation.

A callable object is an object that responds to call by executing associated behavior. Ruby’s main callable objects are Proc objects, lambdas, and method objects. section 14.1

Callable objects let code behave like data:

Create a Proc from a code block, store it in a variable or array, pass it as an argument, and execute it later. section 14.1.1
Use lambdas as a specialized kind of Proc object, or extract methods into method objects for storage and execution. section 14.1
Invoke callable objects with call, square brackets, or the dot-parentheses form; brackets are synonymous with call. section 14.3.2

A callable closure

A method can return a Proc that remembers a value from its creation context: `multiply_by(10)` returns a Proc whose later calls multiply their argument by 10. The preserved context also allows a counter Proc to retain and update its private state across calls. section 14.1.5

pr = Proc.new { puts "Inside a Proc's block" }

Inspect a minimal Proc definition before calling it with `call`; the block becomes the Proc’s executable body. section 14.1.1

How The Well-Grounded Rubyist, Fourth Edition covers it

Cover of The Well-Grounded Rubyist, Fourth Edition

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Related concepts

std::packaged_taskincludes · `std::packaged_task` is a C++ standard library class template that wraps a callable and stores its result in a shared state accessible through a future.
functionincludes · A function is a callable program unit that performs an operation, may accept inputs, and can produce a result or side effect.
classincludes · A class is a programming-language construct that defines a type’s structure or behavior and provides a basis for creating or representing objects.
lambdaincludes · A lambda is a language construct that defines an unnamed function or callable, often as a value.
callused by · A function call is an operation or expression that invokes a function or other callable, optionally supplies arguments, and initiates its execution.
std::threadused by · A C++ standard library class that represents and manages a thread of execution.

This explainer was generated by Manning's knowledge graph from the text of The Well-Grounded Rubyist, Fourth Edition. The section links point to the parts of the book it draws on.