for 循环中递归 $http.get

我使用 Angular 1.5。我有一个查询类别的函数，然后对于每个类别，它查询产品。我想在检索到所有产品后显示一条消息，检索了多少个产品。它输出0。解决方案是什么？

function getProducts() {
  vm.categories = [];
  var prodcount = 0;

  $http.get("localhost/menu/1/categories")
    .then(function(response) {
      var categories = response.data;
      angular.forEach(categories, function(cat) {
        $http.get("localhost/category/" + cat.id + "/products")
          .then(function(response) {
            cat.products = response.data;
            vm.categories.push(cat);
            prodcount += cat.products.length;
          });
      });
      $mdToast.show($mdToast.simple().textContent("retrieved " + vm.categories.length + " categories and, " + prodcount + " products!."));
    });
}

您应该看看异步请求和承诺是如何工作的。 要使您的代码运行，您可以这样做： var 承诺 = []; // 创建一个数组来存储 Promise

angular.forEach(categories, function(cat) {

    // Capture the promise
    var requestPromise = $http.get(...)
    .then(function(response) {
        ...
    });
    promises.push(requestPromise);  // Add it to the array
  });

  // This promise will be resolved when all promises in the array have been resolved as well.
  $q.all(promises).then(function(){
     $mdToast.show(...);
  })

});

但这种方法不太好。您应该尽量减少请求的数量，最好只做一个。

http://www.martin-brennan.com/using-q-all-to-resolve-multiple-promises/ http://andyshora.com/promises-angularjs-explained-as-cartoon.html