Callback

As explained in Refactoring to Rust

A callback function is a function supplied to another operation so that it can be invoked when a specified event or computation completes.

How Refactoring to Rust covers it

How deep it goes

Explains callback registration, C-compatible signatures, raw pointers, null checks, and body parsing, but not general callback abstractions.

Examples

Demonstrates read_body_handler passed to NGINX and used to inspect a request body.

What it assumes

Assumes basic Rust and C interoperability while showing the required function-pointer, calling-convention, and raw-pointer details.

What you can do after

Build callbacks for NGINX FFI integrations and validate raw request pointers before processing data.

How it connects

Connects callbacks with foreign-function interfaces, function pointers, unsafe Rust, raw pointers, and asynchronous request handling.

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Also explained in

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  Secrets of the JavaScript Ninja, Second EditionA function supplied to other code to be invoked later when a condition or event occurs.
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  Data Pipelines with Apache Airflow, Second EditionA callback is a function supplied to another component so that it is invoked when a specified event occurs.
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  The Well-Grounded Rubyist, Fourth EditionA callback is a method or function that a runtime invokes automatically in response to a specified event or lifecycle operation.
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  Functional Programming in Scala, Second EditionA callback is a function supplied to an asynchronous operation so that the operation can report completion or a result later.
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  Functional Programming in JavaScriptA programming pattern in which a function is passed to another operation to be invoked later, often for asynchronous control flow.
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  BDD in Action, Second EditionA hook is a framework callback method that runs before or after a specified software execution event.
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  Build an AI Agent (From Scratch)A callback is a callable supplied to software so it can be invoked automatically at a specified event or stage of execution.
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  React in DepthA callback function is a function supplied to another function or API to be invoked as part of that operation.
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  Build Python Web Apps with StreamlitA callback is a function supplied to another component for execution in response to a later event.
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  The Joy of JavaScriptA callback is a function passed as an argument to another function to be invoked later or in response to an event or condition.
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  Deep Learning with R, Third EditionA Keras callback is an object invoked at specified points during model training or evaluation to monitor state or perform actions.
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  Logs and TelemetryA callback is a function invoked by a framework or runtime in response to a lifecycle event or processing opportunity.
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  Fast Python: High performance techniques for large datasets
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  Machine Learning for Tabular Data: XGBoost, Deep Learning, and AIA Keras callback is an object that runs user-defined actions at specified points during model training or evaluation.
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  D3.js in Action, Third EditionA callback function is a function supplied to another operation so that it can be invoked when a specified event or processing step occurs.
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  Deep Learning with Python, Third EditionA user-defined callback that runs automatically during training to perform extra actions such as monitoring outputs.
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  Essential TypeScript 5, Third EditionA callback is a function supplied to another function or method so that it can be invoked later in response to an operation or event.

Compare how 18 books explain callback →

Related concepts

• call_onceused by · call_once is a threading operation that coordinates callers so a specified callback is successfully executed at most once for a given once-control object.
• replace body with callbackused by · A refactoring technique that extracts unchanged before-and-after code into a function and supplies the varying body as a callback argument.
• forEachused by · The JavaScript Array forEach method invokes a callback once for each assigned element of an array, in ascending index order.
• functionkind of · A function is a defined operation that maps inputs to outputs and, when implemented as a callable program unit, may also produce effects.
• event loopused by · An event loop is a runtime mechanism that repeatedly selects ready events or tasks and dispatches their associated work for execution.

This explainer was generated by Manning's knowledge graph from the text of Refactoring to Rust. The section links point to the parts of the book it draws on.