code: function ( object ) {
        this.__class__ = 'Unique';
  
        if ( 'object' === typeof object )
          this.key = object.key;
  
        this.validate = function ( array ) {
          var value, store = [];
  
          if ( !_isArray( array ) )
            throw new Violation( this, array, { value: Validator.errorCode.must_be_an_array } );
  
          for ( var i = 0; i < array.length; i++ ) {
            value = 'object' === typeof array[ i ] ? array[ i ][ this.key ] : array[ i ];
  
            if ( 'undefined' === typeof value )
              continue;
  
            if ( -1 !== store.indexOf( value ) )
              throw new Violation( this, array, { value: value } );
  
            store.push( value );
          }
  
          return true;
        };
  
        return this;
      }
docs: Unique() or Unique ( { key: foo } )