Javascript Promise - TypeError：无法读取未定义的属性“then”
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Promise - TypeError: Cannot read property 'then' of undefined
提问by Paul Erdos
I think I just need another pair of eyes on this, because I can't get what I'm missing here.
我想我只需要另外一双眼睛，因为我无法得到我在这里缺少的东西。
$scope.checkout = function (form) {
//some code here
function checkoutErrorHandler(error) {
//some code here
}
function displaySuccessMessage() {
$scope.success = true;
cartService.emptyCart();
}
checkoutService.makePayment($scope.payment).then(function (i) {
//some code here
checkoutService.buyProducts($scope.payment, products, i).then(function () {
displaySuccessMessage().then(function(){
$scope.payment = {}; // clear checkout form
$scope.form.reset();
});
return displaySuccessMessage;
},
checkoutErrorHandler
);
}, checkoutErrorHandler);
};
I get "Cannot read property 'then' of undefined" when I call displaySuccessMessage. I've tried refactoring several different ways but cannot get it to work. Does anyone see my mistake?
当我调用 displaySuccessMessage 时，我收到“无法读取未定义的属性‘then’”。我试过重构几种不同的方式，但无法让它工作。有没有人看到我的错误？
回答by Shomz
Your displaySuccessMessagedoes not return a promise. In fact, it doesn't return anything.
你displaySuccessMessage不返回一个承诺。事实上，它不会返回任何东西。
Assuming that cartService.emptyCart()returns a promise, you can modify displaySuccessMessagelike this and it should work just fine:
假设cartService.emptyCart()返回一个 promise，你可以displaySuccessMessage像这样修改它应该可以正常工作：
function displaySuccessMessage() {
$scope.success = true;
return cartService.emptyCart();
}
