Utilizing bindCallback effectively in RXJS6 and DWR: A comprehensive guide

Currently, I am utilizing bindCallback in a way that is now considered deprecated as seen below:

const someMapping = (data) => { return { ... }};

public someCall(id) {
  // Foo.someFunction is function with callbacks
  return this.toObservable(Foo.someFunction, someMapping, id);
}

private toObservable(func, mappingFunction, ...args: any[]) {
  return bindCallback(func, mappingFunction)(...args);
} 

However, aside from the deprecation issue, there is another concern. When I manually call the someFunction:

var callFn = function(data) {...}
var warnFn = function(data) {...}
var errFn = function(data) {...}
Foo.someFunction(id, {callback: callFn, warningHandler: warnFn, errorHandler: errFn})

The function will correctly handle success, warnings, and errors. Since I did not create these DWR callback functions myself and they cannot be changed, the existing documentation does not provide sufficient guidance.

How can I adapt this code to manage all three types of callbacks (success, warning, error) and convert them into observables? Both warnings and errors have the potential to throw an error.

Answer №1

Creating your own observable is the most effective choice.

function customFunction(id) {
  return new Observable(observer => {
                         Foo.customCall(id,
                           {
                            callback: data => {
                                                 observer.next(data);
                                                 observer.complete();
                                               },
                            warningHandler: warn => observer.error(warn),
                            errorHandler: error => observer.error(error)
                          });

                        });

This method is akin to manually invoking customCall but utilizes a stream for emission.

Answer №2

Exploring the bindCallback feature

When using this method, a function func is required with parameters, where the last parameter serves as a callback function that func executes upon completion.

Based on my interpretation of your code

bindCallback(func, mappingFunction)

The actual func in question is identified as Foo.someFunction.

Upon examining Foo.someFunction, it becomes apparent that it does not contain a callback function at its end, which is essential for proper implementation with bindCallback.

This raises doubts about whether this code has ever been functional.

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