Really simple model-validation for Ember.JS (ember-cli), by extending a model with extra validation functionality. Put this file in your models directory and read the instruction in the comment

validation.js

/**
 * Really simple model-validation
 * by extending a model with
 * extra validation functionality
 *
 * Here's how it works
 * /your-app/models/person.js:
 * import DS from 'ember-data';
 * import Validation from 'your-app/models/validation';
 *
 * export default Validation.extend({
 *     firstName :  DS.attr('string'),  // required
 *     lastName :   DS.attr('string'),  // required
 *     age :        DS.attr('integer'), // numeric
 *     town :       DS.attr('string'),  // optional
 *     married :    DS.attr('boolean',
                {defaultValue: false}), // boolean
 *     email :      DS.attr('string'),  // e-mail
 *
 *     requiredFields : ['firstName', 'lastName', 'age'],
 *     numericFields : ['age'],
 *     booleanFields : ['married'],
 *     emailFields : ['email']
 * });
 *
 * Elsewhere in your code:
 * var x = this.store.createRecord('person');
 * x.firstName = 'Austin'; // is OK
 * x.lastName = 'Powers'; // is OK
 * x.town = 'London'; // is OK
 * x.age = 'thirty'; // fails
 * x.married = 'not really'; // fails
 * x.email = 'fax only'; // fails
 * var ok = x.is_valid();
 * if( ok ) {
 *     console.log('OK');
 * }else{
 *     console.log('ERROR');
 *     console.log('All error-messages:', x.get('errors').get('messages'));
 * }
 *
 * or validate fields specificly:
 * if( !this.get('model').is_valid_field( 'firstName' ) ) {
 *     console.log('firstName' + ' has error:');
 *     this.get('model').get('errors').errorsFor( 'firstName' ).forEach(function(err){
 *         console.log(err.message);
 *     });
 * }else{
 *     console.log('firstName' + ' is all good');
 * }
 *
 *
 * Those model-errors are very useful in your templates
 * where you could either use all error-messages:
 * model.errors.messages
 * or field-specific error-messages:
 * model.errors.age.errors (=array where each error-item has a message)
 * More info regarding model-errors at: http://emberjs.com/api/data/classes/DS.Errors.html
 *
 * Setting the error messages can be done in two ways;
 * Override the default-messages directly on the model:
 * export default Validation.extend({
 *     MESSAGE_REQUIRED : "Just anything..",
 *     MESSAGE_NUMERIC : "All I want is a frickin' number",
 *     MESSAGE_BOOLEAN : "Don't you bool me!",
 *     MESSAGE_EMAIL: "Valid email, please..."
 *
 *     firstName : "", // required
 *     lastName : "", // required
 *     age : 0, // numeric
 *     town : "", // optional
 *     married : false, // boolean
 *     email : "", // e-mail
 *
 *     requiredFields : ['firstName', 'lastName', 'age'],
 *     numericFields : ['age'],
 *     booleanFields : ['married'],
 *     emailFields : ['email']
 * });
 *
 * or pass your messages when calling the validation methods:
 * x.is_valid({
 *   message_required: "Just anything..",
 *   message_numeric: "All I want is a frickin' number",
 *   message_boolean: "Don't you bool me!",
 *   message_email: "Valid email, please..."
 * });
 * x.is_valid_field('firstName', {
 *   message_required: "Just anything..",
 *   message_numeric: "All I want is a frickin' number",
 *   message_boolean: "Don't you bool me!",
 *   message_email: "Valid email, please..."
 * });
 *
 *
 * @author sejKo
 * @version 0.2.1
 *
 */
import DS from 'ember-data';

export default DS.Model.extend({
    /**
     * Override this field by populating an array
     * with names of fields which are required
     */
    requiredFields : [],
    /**
     * Override this field by populating an array
     * with names of fields which must be numeric
     */
    numericFields : [],
    /**
     * Override this field by populating an array
     * with names of fields which must be booleans
     */
    booleanFields : [],
    /**
     * Override this field by populating an array
     * with names of fields which must be valid e-mail adresses
     */
    emailFields : [],

    /**
     * Default messages
     */
    MESSAGE_REQUIRED : 'This field is required',
    MESSAGE_NUMERIC : 'This field must be numeric',
    MESSAGE_BOOLEAN : 'This field must be True / False',
    MESSAGE_EMAIL : 'This field must contain a valid e-mail address',

    /**
     * Public method to call to validate a model instance
     *
     * How to set field-messages :
     * myModel.is_valid({
     *   message_required: "Just anything..",
     *   message_numeric: "All I want is a frickin' number",
     *   message_boolean: "Don't you bool me!",
     *   message_email: "Valid email, please..."
     * });
     *
     * @param object optional
     * @return boolean
     */
     is_valid : function ( messages ) {
        var msgs = messages || {};
        var message_required = msgs.message_required || null;
        var message_numeric  = msgs.message_numeric || null;
        var message_boolean  = msgs.message_boolean || null;
        var message_email    = msgs.message_email || null;

        this.get('errors').clear();

        var ok = true;

        if( !this._is_valid_required( message_required ) ){ ok = false; }
        if( !this._is_valid_numeric(  message_numeric )  ){ ok = false; }
        if( !this._is_valid_boolean(  message_boolean )  ){ ok = false; }
        if( !this._is_valid_email(    message_email )    ){ ok = false; }

        return ok;
    },
    /**
     * Public method to call to validate a model instance
     *
     * How to set field-messages :
     * myModel.is_valid_field('firstName', {
     *   message_required: "Just anything..",
     *   message_numeric: "All I want is a frickin' number",
     *   message_boolean: "Don't you bool me!",
     *   message_email: "Valid email, please..."
     * });
     *
     * @param string
     * @param object optional
     * @return boolean
     */
     is_valid_field : function (field, messages) {
        var msgs = messages || {};
        var message_required = msgs.message_required || null;
        var message_numeric  = msgs.message_numeric || null;
        var message_boolean  = msgs.message_boolean || null;
        var message_email    = msgs.message_email || null;

        if( this.get('errors').has( field ) ) {
            this.get('errors').errorsFor( field ).clear();
        }

        var ok = true;

        if( this.requiredFields.indexOf(field) >= 0 && !this._is_valid_required_field( field, message_required ) ){ ok = false; }
        if( this.numericFields.indexOf(field) >= 0  && !this._is_valid_numeric_field(  field, message_numeric )  ){ ok = false; }
        if( this.booleanFields.indexOf(field) >= 0  && !this._is_valid_boolean_field(  field, message_boolean )  ){ ok = false; }
        if( this.emailFields.indexOf(field) >= 0    && !this._is_valid_email_field(    field, message_email )    ){ ok = false; }

        return ok;
    },

    /**
     * Allows anything that isn't empty
     * for the this.requiredFields list
     *
     * @param string optional
     * @return boolean
     */
    _is_valid_required : function ( message ) {
        var msg = message || this.MESSAGE_REQUIRED;
        var self = this;
        var ok = true;
        this.get('requiredFields').forEach( function(field /*, index*/){
            if( !self._is_valid_required_field(field, msg) ) {
                ok = false;
            }
        });
        return ok;
    },
    /**
     * Allows anything that isn't empty
     *
     * @param string
     * @param string optional
     * @return boolean
     */
    _is_valid_required_field : function (field, message) {
        var msg = message || this.MESSAGE_REQUIRED;
        var check = typeof check === 'string' ? this.get( field ).trim() : this.get( field );
        if( check === '' ){
            this.get('errors').add(field, msg);
            return false;
        }
        return true;
    },

    /**
     * Allows numbers as strings and numbers
     * for the this.numericFields list
     *
     * @param string optional
     * @return boolean
     */
    _is_valid_numeric : function ( message ) {
        var msg = message || this.MESSAGE_NUMERIC;
        var self = this;
        var ok = true;
        this.get('numericFields').forEach( function(field /*, index*/){
            if( !self._is_valid_numeric_field(field, msg) ) {
                ok = false;
            }
        });
        return ok;
    },
    /**
     * Allows numbers as strings and numbers
     *
     * @param string
     * @param string optional
     * @return boolean
     */
    _is_valid_numeric_field : function (field, message) {
        var msg = message || this.MESSAGE_NUMERIC;
        var check = typeof check === 'string' ? this.get( field ).trim() : this.get( field );
        if( isNaN(parseFloat(check)) || !isFinite(check) ){
            this.get('errors').add(field, msg);
            return false;
        }
        return true;
    },

    /**
     * Allows booleans only
     * for the this.booleanFields list
     *
     * @param string optional
     * @return boolean
     */
    _is_valid_boolean : function ( message ) {
        var msg = message || this.MESSAGE_BOOLEAN;
        var self = this;
        var ok = true;
        this.get('booleanFields').forEach( function(field /*, index*/){
            if( !self._is_valid_boolean_field(field, msg) ) {
                ok = false;
            }
        });
        return ok;
    },
    /**
     * Allows booleans only
     *
     * @param string
     * @param string optional
     * @return boolean
     */
    _is_valid_boolean_field : function (field, message) {
        var msg = message || this.MESSAGE_BOOLEAN;
        var check = this.get( field );
        if( typeof check !== 'boolean' || (typeof check === 'object' && typeof check.valueOf() === 'boolean') ){
            this.get('errors').add(field, msg);
            return false;
        }
        return true;
    },

    /**
     * Allows valid e-mail adresses only
     * for the this.emailFields list
     *
     * @param string optional
     * @return boolean
     */
    _is_valid_email : function ( message ) {
        var msg = message || this.MESSAGE_EMAIL;
        var self = this;
        var ok = true;
        this.get('emailFields').forEach( function(field /*, index*/){
            if( !self._is_valid_email_field(field, msg) ) {
                ok = false;
            }
        });
        return ok;
    },
    /**
     * Allows valid e-mail adresses only
     *
     * @param string
     * @param string optional
     * @return boolean
     */
    _is_valid_email_field : function (field, message) {
        var msg = message || this.MESSAGE_EMAIL;
        var check = this.get( field );
        var re = /[A-Z0-9._%+-]+@[A-Z0-9.-]+.[A-Z]{2,4}/igm;
        if( check !== '' && !re.test( check ) ){
            this.get('errors').add(field, msg);
            return false;
        }
        return true;
    }
});