Angular指令没有获取服务数据

Question

我的服务NavData

angular.module('navData', []).
    factory('NavData', function() {
        var navData = {};
        navData.depth = 0;
        navData.category_id = "";
        navData.category_name = "";
        navData.subcategory_id = "";
        navData.subcategory_name = "";
        return navData;
    });

在某些页面上从ui-router接收值:

  var category = { 
    name: 'category',
    parent: site,
    url: '/categories/:category_id',
    onEnter: function(NavData, $stateParams){
      NavData.depth = 1;
      NavData.category_id = $stateParams.category_id;
      console.log(NavData);         
    },
    views: {
      'navigation': {
      templateUrl: 'partials/category-menu.html'
      },
      'content': {
      templateUrl: 'partials/category-images.html'
      }
    }
  };

出现在所有页面上的指令应该监视服务中的更改并将其反映在自定义的痕迹导航功能中:

  .directive('breadcrumb', ['NavData', function(NavData){
    return {
      templateUrl: 'partials/breadcrumb.html',
      link: function(scope, elm, attrs, ctrl){
        scope.depth            = NavData.depth;
        scope.category_id      = NavData.category_id;
        scope.category_name    = NavData.category_name;
        scope.subcategory_name = NavData.subcategory_name;

        var doStuff = function(navdata){
          console.log("watching depth: " + navdata.depth);
          console.log("watching cat_id: "+ navdata.category_id);
        };
        scope.$watch(NavData.depth, doStuff(NavData), true);
        scope.$watch(NavData.category_id, doStuff(NavData), true);
      }

    };
  }])

但是,范围.$ watch似乎不起作用.这是我的日志:

watching depth: 0 directives.js:28
watching cat_id:  directives.js:29
watching depth: 0 directives.js:28
watching cat_id:  directives.js:29
Object {depth: 1, category_id: "1", category_name: "", subcategory_id: "", subcategory_name: ""} app.js:25

我究竟做错了什么？

Answer 1

您的第一个错误出现在第scope.$watch()一个参数中:它是在给定值中计算的表达式(字符串)scope,或者是返回值的函数; 存储该值,并在每个摘要周期运行该函数; 如果新值不同,则触发侦听器(第二个参数).

所以第一次修正是:

scope.$watch(function() {
    return NavData.depth,
}, .../*other arguments, see below*/);

现在第二个论点也是错的!它应该是一个函数,你提供一个函数的返回值(顺便说一句,它是未定义的doStuff).第二个参数函数接收新值(由上面第一个参数返回),旧值和范围.在您的情况下,您不关心新/旧值.所以完整的解决方案应该是:

scope.$watch(function() { // decide the watched value
    return NavData.depth,
}, function() { // what to do when the value changes
    // do stuff and reference NavData normally
});