Cannot read property 'simpleforcast' of undefined ？ 这究竟是什么错？？

想着看教程 写一个类似Currently的天气预报的Chrome扩展程序 ，我想先在视图中调用这个Weather api的结果，结果就gg了。实在没辙了！

/**
 * Created by lv on 2015/11/7.
 */
var app = angular.module('myapp',[]);

app.provider('Weather',function(){
    var apiKey = "";
    this.getUrl = function(type,ext){
        return "http://api.wunderground.com/api/" + this.apiKey + "/" + type + "/q/" + ext + '.json';
    };
    this.$get = function($q,$http){
        var self = this;
        return {
            //服务对象
            getWeatherForecast: function(city){
                var d = $q.defer();
                $http({
                    method: 'GET',
                    url: self.getUrl("forecast",city),
                    cache:true
                }).success(function(data){
                    //Wunderweather接口返回
                    //嵌套在forecast.simpleforcast属性内的forecast对象
                    d.resolve(data.forcast.simpleforcast);
                }).error(function(err){
                    d.reject(err);
                });
                return d.promise();
            }
        }
    };
    this.setApiKey = function(key){
        if(key) this.apiKey = key;
    };

});
app.config(function(WeatherProvider){
    WeatherProvider.setApiKey('39fb2e6f07af19f7-Yzz');
});

app.controller('mainController',function($scope,$timeout,Weather){
    //构建date对象
    $scope.date = {};
    //时钟
    var upDateTime = function(){
        $scope.date.raw = new Date();
        $timeout(upDateTime,1000);
    };
    //启动函数
    upDateTime();

    $scope.weather = {};
    Weather.getWeatherForecast("CA/San_Francisco")
        .then(function(data){
            $scope.weather.forcast  = data;
        });
});

<div ng-controller="mainController">
    <div id="forecast">     
        <pre>{{ weather.forecast | json }}</pre> 
    </div>
</div>

第一个错误，有位哥们帮我解决了，第二个Cannot read property 'simpleforcast' of undefined 该怎么办-。-！！！ 我这样写能获取到api吗？

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$http.get 就已经返回 promise 了