How to use logical operators inside bind formulas in ExtJS?

Question

I have 3 input fields in a form and want to make the third input enabled only when the first two inputs have values.

This doesn't seem to work:

Ext.define('MyApp.view.myobj.MyPanel', {
    extend:'Ext.Panel',

    viewModel: {},

    items: [{
        xtype: 'form',
        defaultType: 'textfield',
        items: [
            {fieldLabel: 'Field 1', reference: 'field1', publishes: 'value'},
            {fieldLabel: 'Field 2', reference: 'field2', publishes: 'value'},
            {
                fieldLabel: 'Field 3', 
                bind: {
                    disabled: '{!field1.value} || {!field2.value}'
                }
            },            
        ],
    }],
});

Fiddle

Answer 1

In the view model, add a formula to return the value for {!field1.value} || {!field1.value}

As per the fiddle:

viewModel: {
    formulas: {
        something: {
            bind: {
                x: '{!field1.value}',
                y: '{!field2.value}'
            },

            get: function (data) {
                if (data.x || data.y) return true;
                else return false;
            }
        }
    }
},

items: [{
    xtype: 'form',
    defaultType: 'textfield',
    bodyPadding: 10,
    items: [
        {fieldLabel: 'Field 1', reference: 'field1', publishes: 'value'},
        {fieldLabel: 'Field 2', reference: 'field2', publishes: 'value'},
        {
            fieldLabel: 'Field 3', 
            bind: {
                disabled: "{something}"
            }
        },            
    ],

}]

Answer 2

Add a formulas configuration to your ViewModel like this:

formulas : {
        showSomeComponent : function (get) {
            return get('isAuthorized') && !get('isDisabled');
        }
    }

http://docs.sencha.com/extjs/5.1.0/Ext.app.ViewModel.html#cfg-formulas