angular.js - angular $q问题

Question

function getMenus() {
    if (!localStorage.getItem('menus')) {
        var defer = $q.defer();
        $http.get('api/menu').success(function (res) {
            // scope.menuList = res;
            localStorage.setItem('menus', res)
            defer.resolve();
            return defer.promise;
        }).error(function (err) {
            defer.reject()
            return defer.promise;
        });

    }
}
getMenus().then(function () {
    scope.menuList = localStorage.getItem('menus')
})

返回结果是angular.min.js:107 TypeError: Cannot read property 'then' of undefined

请问哪里错了。。。。。

Answer 1

The error is reported because the getMenus function has no return value, js returns undefined by default, and then raises then on undefined, so the error is reported
Solution:

Initialized in the first line of getMenus

var defer = $q.defer()

Finally return defer.promise as the return value
In the end it should look like this

function getMenus() {
    var defer = $q.defer()
    if (...) {...}
    return defer.promise
}

Of course there will be problems if you return promises in the success and error callbacks

Answer 2

function getMenus() {

    var defer = $q.defer();
    
    if (!localStorage.getItem('menus')) {
        
        $http.get('api/menu').success(function (res) {
            // scope.menuList = res;
            localStorage.setItem('menus', res)
            defer.resolve();
        }).error(function (err) {
            defer.reject()
        });

    }
    
    return defer.promise;
}