Override members of this class. Overridden methods can be invoked via
{@link Ext.Base#callParent}.

Ext.define('My.Cat', {
constructor: function() {
alert("I'm a cat!");
}
});

My.Cat.override({
constructor: function() {
alert("I'm going to be a cat!");

this.callParent(arguments);

alert("Meeeeoooowwww");
}
});

var kitty = new My.Cat(); // alerts "I'm going to be a cat!"
// alerts "I'm a cat!"
// alerts "Meeeeoooowwww"

As of 4.1, direct use of this method is deprecated. Use {@link Ext#define Ext.define}
instead:

Ext.define('My.CatOverride', {
override: 'My.Cat',
constructor: function() {
alert("I'm going to be a cat!");

this.callParent(arguments);

alert("Meeeeoooowwww");
}
});

The above accomplishes the same result but can be managed by the {@link Ext.Loader}
which can properly order the override and its target class and the build process
can determine whether the override is needed based on the required state of the
target class (My.Cat).

@param {Object} members The properties to add to this class. This should be
specified as an object literal containing one or more properties.
@return {Ext.Base} this class
@static
@inheritable
@markdown
@deprecated 4.1.0 Use {@link Ext#define Ext.define} instead
function(members) {
            var me = this,
                enumerables = Ext.enumerables,
                target = me.prototype,
                cloneFunction = Ext.Function.clone,
                name, index, member, statics, names, previous;

            if (arguments.length === 2) {
                name = members;
                members = {};
                members[name] = arguments[1];
                enumerables = null;
            }

            do {
                names = []; // clean slate for prototype (1st pass) and static (2nd pass)
                statics = null; // not needed 1st pass, but needs to be cleared for 2nd pass

                for (name in members) { // hasOwnProperty is checked in the next loop...
                    if (name == 'statics') {
                        statics = members[name];
                    } else if (name == 'inheritableStatics'){
                        me.addInheritableStatics(members[name]);
                    } else if (name == 'config') {
                        me.addConfig(members[name], true);
                    } else {
                        names.push(name);
                    }
                }

                if (enumerables) {
                    names.push.apply(names, enumerables);
                }

                for (index = names.length; index--; ) {
                    name = names[index];

                    if (members.hasOwnProperty(name)) {
                        member = members[name];

                        if (typeof member == 'function' && !member.$className && member !== Ext.emptyFn && member !== Ext.identityFn) {
                            if (typeof member.$owner != 'undefined') {
                                member = cloneFunction(member);
                            }

                            //<debug>
                            if (me.$className) {
                                member.displayName = me.$className + '#' + name;
                            }
                            //</debug>

                            member.$owner = me;
                            member.$name = name;

                            previous = target[name];
                            if (previous) {
                                member.$previous = previous;
                            }
                        }

                        target[name] = member;
                    }
                }

                target = me; // 2nd pass is for statics
                members = statics; // statics will be null on 2nd pass
            } while (members);

            return this;
        }