The jQuery.getJSON() method seems to ignore the normal rules of scoping within JavaScript.

Given code such as this...

someObject = {
    someMethod: function(){
        var foo;

        $.getJSON('http://www.somewhere.com/some_resource', function(data){
            foo = data.bar;
        });

        alert(foo); // undefined
    }
}

someObject.someMethod();

Is there a best practice for accessing the value of the variable outside of the getJSON scope?