Aliases

In this context, an "alias" is a proxy property or method inside a target class. It is responsible for forwarding interaction to the original property or method, inside the concern class instance. Aliases are created automatically by the use() class decorator.

• Properties & Methods
• If property or method already exists

Properties & Methods

When injecting a concern into a target class, the concern's public properties and methods are defined as "aliases" (aka. proxy properties or methods), in the target class' prototype (see PROVIDES symbol for additional details).

Consider the following example:

import { use, AbstractConcern } from "@aedart/support/concerns";

class Levels extends AbstractConcern {
    get level() { /* ...not shown */ }
    set level(value) { /* ...not shown */ }
    clear() { /* ...not shown */ }
}

@use(Levels)
class Recorder {}

The aliasing mechanism will transform the target class into something that very roughly corresponds to this:

import {
    use,
    CONCERNS,
    AbstractConcern
} from "@aedart/support/concerns";

class Levels extends AbstractConcern {
    get level() { /* ...not shown */ }
    set level(value) { /* ...not shown */ }
    clear(level) { /* ...not shown */ }
}

class Recorder {
    // ...private concerns container not shown...

    // get level "alias"
    get level() {
        return this[CONCERNS].get(Levels)['level'];
    }

    // set level "alias"
    set level(value) {
        this[CONCERNS].get(Levels)['level'] = value;
    }

    // method clear "alias"
    clear(...args) {
        return this[CONCERNS].get(Levels)['clear'](...args);
    }
}

See Manual interaction and Conflict Resolution for additional details.

If property or method already exists

When a property or method from a concern already exists in the target class' prototype chain¹, then NO Alias is defined. Said differently, the use() class decorator does NOT overwrite a target class' properties or methods.

class Label extends AbstractConcern {
    get name() { /* ...not shown.. */ }
    set name(v) { /* ...not shown.. */ }
}

@use(Label) // Label's "name" property is NOT aliased
class Battery {

    // Battery's get/set "name" remains untouched by concern
    get name() { /* ...not shown.. */ }
    set name(v) { /* ...not shown.. */ }
}

¹: Inherited properties and methods are also respected.

See Conflict Resolution for additional details.