docs: collecting parameter docs + formatting

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Ilkka Seppälä
2024-03-29 14:13:26 +02:00
parent ea7bc2a4eb
commit f80cc468b2
23 changed files with 1191 additions and 794 deletions
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@@ -11,7 +11,8 @@ tag:
## Intent
Callback is a piece of executable code that is passed as an argument to other code, which is expected to call back (execute) the argument at some convenient time.
Callback is a piece of executable code that is passed as an argument to other code, which is expected to call back (
execute) the argument at some convenient time.
## Also known as
@@ -22,15 +23,17 @@ Callback is a piece of executable code that is passed as an argument to other co
Real world example
> We need to be notified after the executing task has finished. We pass a callback method for the executor and wait for it to call back on us.
> We need to be notified after the executing task has finished. We pass a callback method for the executor and wait for
> it to call back on us.
In plain words
> Callback is a method passed to an executor which will be called at a defined moment.
> Callback is a method passed to an executor which will be called at a defined moment.
Wikipedia says
> In computer programming, a callback, also known as a "call-after" function, is any executable code that is passed as an argument to other code; that other code is expected to call back (execute) the argument at a given time.
> In computer programming, a callback, also known as a "call-after" function, is any executable code that is passed as
> an argument to other code; that other code is expected to call back (execute) the argument at a given time.
**Programmatic Example**
@@ -69,8 +72,8 @@ public final class SimpleTask extends Task {
Finally, here's how we execute a task and receive a callback when it's finished.
```java
var task = new SimpleTask();
task.executeWith(() -> LOGGER.info("I'm done now."));
var task=new SimpleTask();
task.executeWith(()->LOGGER.info("I'm done now."));
```
## Class diagram
@@ -89,13 +92,15 @@ Use the Callback pattern when
* GUI frameworks often use callbacks for event handling, such as user interactions (clicks, key presses)
* Node.js heavily relies on callbacks for non-blocking I/O operations
* Frameworks that deal with asynchronous operations, like Promises in JavaScript, use callbacks to handle the resolution or rejection of asynchronous tasks
* Frameworks that deal with asynchronous operations, like Promises in JavaScript, use callbacks to handle the resolution
or rejection of asynchronous tasks
## Consequences
Benefits:
* Decouples the execution logic of an operation from the signaling or notification logic, enhancing modularity and reusability
* Decouples the execution logic of an operation from the signaling or notification logic, enhancing modularity and
reusability
* Facilitates asynchronous processing, improving the responsiveness and scalability of applications
* Enables a reactive programming model where components can react to events as they occur
@@ -103,16 +108,21 @@ Trade-offs:
* Callback hell or pyramid of doom: Deeply nested callbacks can lead to code that is hard to read and maintain
* Inversion of control can lead to harder-to-follow code flow, making debugging more challenging
* Potential issues with error handling, especially in languages or environments where exceptions are used, as errors might need to be propagated through callbacks
* Potential issues with error handling, especially in languages or environments where exceptions are used, as errors
might need to be propagated through callbacks
## Related patterns
[Observer](https://java-design-patterns.com/patterns/observer/): Callbacks can be seen as a more dynamic and lightweight form of the Observer pattern, with the ability to subscribe and unsubscribe callback functions dynamically
[Command](https://java-design-patterns.com/patterns/command/): Callbacks can be implemented as Command objects in scenarios where more flexibility or statefulness is required in the callback operation
[Promise](https://java-design-patterns.com/patterns/promise/): In some languages or frameworks, Promises or Futures can be used to handle asynchronous operations more cleanly, often using callbacks for success or failure cases
[Observer](https://java-design-patterns.com/patterns/observer/): Callbacks can be seen as a more dynamic and lightweight
form of the Observer pattern, with the ability to subscribe and unsubscribe callback functions dynamically
[Command](https://java-design-patterns.com/patterns/command/): Callbacks can be implemented as Command objects in
scenarios where more flexibility or statefulness is required in the callback operation
[Promise](https://java-design-patterns.com/patterns/promise/): In some languages or frameworks, Promises or Futures can
be used to handle asynchronous operations more cleanly, often using callbacks for success or failure cases
## Real world examples
* [CyclicBarrier](http://docs.oracle.com/javase/7/docs/api/java/util/concurrent/CyclicBarrier.html#CyclicBarrier%28int,%20java.lang.Runnable%29) constructor can accept a callback that will be triggered every time a barrier is tripped.
* [CyclicBarrier](http://docs.oracle.com/javase/7/docs/api/java/util/concurrent/CyclicBarrier.html#CyclicBarrier%28int,%20java.lang.Runnable%29)
constructor can accept a callback that will be triggered every time a barrier is tripped.
* [JavaScript: The Good Parts](https://amzn.to/3TiQV61)
* [Node.js Design Patterns - Third edition: Design and implement production-grade Node.js applications using proven patterns and techniques](https://amzn.to/3VssjKG)