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2.3.2 Static Properties

You have likely noticed by now that static properties are handled a bit differently than both static methods and non-static properties. This difference is due to pre-ECMAScript 5 limitations and is discussed at length in the Static Implementation section.

Static properties are read from and written to using the static accessor method $(). This method name was chosen because the $ prefix is common in scripting languages such as BASH, Perl (for scalars) and PHP. The accessor method accepts two arguments, the second being optional. If only the first argument is provided, the accessor method acts as a getter, as in Figure 2.19's getTotalCount():

    return this.$('_count');

If the second argument is provided, it acts as a setter, as in __construct():

    this.__self.$( '_count',
        this.__self.$('count') + 1
    );

Setting undefined values is supported. The delete operator is not supported, as its use is both restricted by the language itself and doesn't make sense to use in this context. As hinted by the example above, the increment and decrement operators (++ and --) are not supported because JavaScript does not permit returning values by reference.

It is important to understand that, currently, the accessor method cannot be omitted. Consider the following example:

    var Foo = Class( 'Foo',
        {
            'public static bar': 'baz',
        },

        SubFoo = Class( 'SubFoo' ).extend( Foo, {} )
    ;

    // correct
    Foo.$( 'bar, 'baz2' );
    Foo.$('bar');               // baz2
    SubFoo.$('bar');            // baz2
    SubFoo.$( 'bar', 'baz3' );
    Foo.$('bar');               // baz3

    // INCORRECT
    Foo.bar = 'baz2';
    Foo.bar;                    // baz2
    SubFoo.bar;                 // undefined

Figure 2.20: Static accessor method cannot be omitted