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2.5 Method Proxies

'proxy [keywords] name': destmember

Declare a proxy method name, having optional additional keywords keywords, that invokes a method of the same name on object destmember and returns its result.

Method proxies help to eliminate boilerplate code for calling methods on an encapsulated object—a task that is very common with proxy and decorator design patterns.

var Pidgin = Class( 'Pidgin',
{
    'private _name': 'Flutter',

    'public cheep': function( chirp )
    {
        return this._name + ": cheep " + chirp;
    }

    'public rename': function( name )
    {
        this._name = ''+name;
        return this;
    }
} );

var IratePidginCheep = Class( 'IratePidginCheep',
{
    'private _pidgin': null,

    __construct: function( pidgin )
    {
        this._pidgin = pidgin;
    }

    // add our own method
    'public irateCheep': function( chirp )
    {
        return this._pidgin.cheep( chirp ).toUpperCase();
    },

    // retain original methods
    'proxy cheep':  '_pidgin',
    'proxy rename': '_pidgin',
} );

var irate = IratePidginCheep( Pidgin() );

irate.cheep( 'chirp' );
// "Flutter: cheep chirp"
irate.setName( 'Butter' ).cheep( 'chirp' );
// "Butter: cheep chirp"
irate.irateCheep( 'chop' );
// "BUTTER: CHEEP CHOP"

Consider some object O whoose class uses method proxies.

• All arguments of proxy method O.name are forwarded to destmember.name untouched.
• The return value provided by destmember.name is returned to the caller of O.name untouched, except that
  • If destmember.name returns destmember (that is, returns this), it will be replaced with O; this ensures that destmember remains encapsulated and preserves method chaining.
• If destmember is not an object, calls to O.name will immediately fail in error.
• If destmember.name is not a function, calls to O.name will immediately fail in error.
• N.B.: Static method proxies are not yet supported.