save-instance

Why save-instance

If you have a class like:

class Test {
    constructor (...args) {}
}

And you initialize some instances in a module (ie. a bootstrap module), like:

const a = new Test(...args);

Since you don't know what module would use them, you should export them by exports or global

Yet both exports and global seems not perfect for this case.

• For exports, you should require that bootstrap module to use the instances, which is puzzle
• For global, you should handle the namespace problem carefully

Maybe a better way is to bind the instances with the class itself, like:

const a1 = Test.getInstance('A');

Now it seems more reasonable, as "to get the Test instance named 'A' "

Of course, you should initalize and name it before using.

new Test(...args).saveInstance('A');
// or
Test.saveInstance('A', ...args);

How to use

Decoration is supposed as the best way to use this

const savable = require('save-instance');

@savable()
class Test {...}

Yet decorator is not implemented till current version (v7.6), use it like

class Test {...}
savable()(Test);

Other uses

Lazy mode

Maybe we want instances initialized in a lazy mode. Just use it like this:

Test.saveLazyInstance('A', ...args);

Singleton

Use default name '' to pretend as a singleton instance

new Test(...args).saveInstance();
const test =  Test.getInstance();

Options

If you want to preprocess arguments, use options.preprocessArguments(name, ...args)

@savable({
    preprocessArguments(name, ...args) {
        return ['arg1', 'arg2', 'arg3'];
    }
})
class Test {}

If you want to preprocess instance, use options.preprocessInstance(instance, name, ...args)

@savable({
    preprocessInstance(instance, name) {
        instance.name = name;
        return instance;
    }
})
class Test {}

If you want to set a default name, or want to map some names into one, use options.defaultName and options.map

@savable({
    defaultName: 'foo',
    map: {
        'bar': 'foo',
        'baz': 'foo',
    },
})
class Test {}

Notice that the default name is undefined and maps null to undefined.