Edit in JSFiddle

Ext.define('Person', {
    extend: 'Ext.data.Model',
    fields: [
        {name:"name", type:'string'},
        {name:"age", type:"int"},
        {name:"hobby", type:"string"}
    ],
    validations: [
        {type: 'presence', field: 'name', message: 'You have to enter a name, silly'},
        {type: 'presence', field: 'age', message: 'You must specify an age'},
        {type: 'presence', field: 'hobby', message: 'You must enter a hobby'},
        {type: 'length', field: 'hobby', min:5, message: 'You must specify a hobby with more than 4 characters'}
    ]
})
Ext.define('Form', {
    extend: 'Ext.form.Panel',
    alias: 'widget.peopleform',
    bodyPadding: 10,
    border: false,
    initComponent: function() {
        var me = this;
        Ext.applyIf(me, {
            defaults: {
                width: 250,
                labelWidth: 70
            },
            autoShow: true,
            renderTo: Ext.getBody(),
            items: [
                {
                    xtype: 'textfield',
                    name: 'name',
                    fieldLabel: 'Name'
                },
                {
                    xtype: 'numberfield',
                    name: 'age',
                    fieldLabel: 'Age',
                    value: 20
                },
                {
                    xtype: 'textfield',
                    name: 'hobby',
                    fieldLabel: 'Hobby'
                }
            ]
        });
        me.callParent(arguments);
    }
})
Ext.override(Ext.form.Basic, {
    loadRecord: function(record) {
        this._record = record;
        this.setModelValidations(record.validations);
        return this.setValues(record.data);
    },
    setModelValidations: function(validations) {
        var fields = this.getFields(), i;
        for(i=0;i<validations.length;i++) {
            var fieldMatch = this.findField(validations[i].field);
            if(fieldMatch) {
                fieldMatch.setModelFieldValidation(validations[i])
            }
        }
    }
})
Ext.override(Ext.form.field.Base, {
    setModelFieldValidation: function(validation) {
        this.modelValidations = Ext.isArray(this.modelValidations) ? this.modelValidations : [];
        this.modelValidations.push(validation);
    },
    getModelErrors: function(value) {
        var errors      = Ext.create('Ext.data.Errors'),
            validations = this.modelValidations,
            validators  = Ext.data.validations,
            length, validation, field, valid, type, i;

        if (validations) {
            length = validations.length;

            for (i = 0; i < length; i++) {
                validation = validations[i];
                field = validation.field || validation.name;
                type  = validation.type;
                valid = validators[type](validation, value);

                if (!valid) {
                    errors.add({
                        field  : field,
                        message: validation.message || validators[type + 'Message']
                    });
                }
            }
        }
        return errors;
    },
    validateValue: function(value) {
        var me = this,
            errors = me.getErrors(value),
            modelErrors = me.getModelErrors(value),
            isValid = Ext.isEmpty(errors) && modelErrors.isValid();
        if (!me.preventMark) {
            if (isValid) {
                me.clearInvalid();
            }
            else {
                if(!modelErrors.isValid()) { modelErrors.each(function() { errors.push(this.message); }) }
                me.markInvalid(errors);
            }
        }
        return isValid;
    }
})
var window = Ext.create('Ext.window.Window', {
    title: 'Test Validations',
    items: [{xtype:'peopleform'}],
    width:400,
    autoShow:true,
    bbar: [{
        text: 'Save',
        handler: function(btn,e,opts) {
            var form = btn.up('window').down('form').getForm();
            var record = form.getRecord();
            if(!form.isValid()) {
                Ext.Msg.alert('Attention','You need to fix some errors!');
                return false;                
            }
            else {
                record.set(form.getValues())            
            }
        }    
    }],
    listeners: {
        render: function(window) {
            window.down('form').getForm().loadRecord(Ext.create('Person'));    
        }    
    }           
})