SettingsManager / Promiseifyish Example

This page illustrates the general use of SettingsManager, as well as an example with a promiseified version, using Promiseifyish.

There are some advantages to using a promise-style API over standard callback style. In general, the code flows better and is easier to read with Promises.

Compare the two code samples below to see the difference between the callback style and the promise style.

Settings Manager Code


        // Handlers
        function onSettingsLoaded(settings) {
            console.log('loaded', settings);
        }
        function onSettingsSaved() {
            console.log('settings saved');
        }
        function onError(error) {
            console.log('error:', error);
        }

        // Start with a load
        var settingsManager = new SettingsManager();
        settingsManager.load(function onLoad(settings) {
            // Handle the load response and start a save
            onSettingsLoaded(settings);
            settingsManager.save({one: 1, two: 'two'}, function onSave() {
                // Handle the save response and start another load
                onSettingsSaved();
                settingsManager.load(function onLoad(settings) {
                    // Handle the load response and start another save
                    onSettingsLoaded(settings);
                    settingsManager.save({three: 3, two: 2}, function onSave() {
                        // Handle the save response and start another load
                        onSettingsSaved();
                        settingsManager.load(function onLoad(settings) {
                            // Handle the load response
                            onSettingsLoaded(settings);
                        }, onError);
                    }, onError);
                }, onError);
            }, onError);
        }, onError);

Things to note

The code indents with each callback
The onError hander is passed in for each function call

Promiseified Settings Manager Code


// Promiseify a SettingsManager instance
var promisifiedSettingsManager = Promiseify(new SettingsManager());

promisifiedSettingsManager.load()
.then(onSettingsLoaded)
.then(() => promisifiedSettingsManager.save({one: 1, two: 'two'}))
.then(onSettingsSaved)
.then(() => promisifiedSettingsManager.load())
.then(onSettingsLoaded)
.then(() => promisifiedSettingsManager.save({three: 3, two: 2}))
.then(onSettingsSaved)
.then(() => promisifiedSettingsManager.load())
.then(onSettingsLoaded)
.catch(onError);

Things to note

There is less code
There are no code indents
The code reads easily and logically
The onError hander is passed in exactly once

This example shows code for both the standard usage as well as the promiseified usage, running next to each other. Notice how the results are the same; this shows that the promisiefied version retains API functionality.