如果可能的话,我需要一些帮助。我是AngularJS的新手,无法弄清楚如何处理我遇到的问题。基本上,问题是我有两个异步初始化的不同数组,同时最终将两个数据存储在同一个数组中,并在多个项的for循环中执行此操作。我遇到的错误是,当它加载正确数量的项目时,它会显示所有不同的用户数据,但不会显示不同的图片。每个条目显示的图片相同。在整个代码部分的末尾,您可以找到:
userPromise.then(function(user){
picPromise.then(function(url){
newfriendsinfo.push({
id: newfriendid,
name: user.val().name,
email: user.val().email,
agreed: newfriendagreed,
profilepicture: url
});
}).then(function(){
if (newfriendsinfo.length == newfriends.length){
deferred.resolve(newfriendsinfo);
}
});
});
我很确定这就是我的问题所在。它在不使用新图片时查找新用户数据。但是,我不确定如何处理这个问题。我已经查看了多个延迟变量和$ q.all,但我不能完全看到我应该如何解决这个问题。您可以在下面找到完整的相关代码。非常感谢您的帮助:)
var friendsRef = firebase.database().ref('friendships/' + firebase.auth().currentUser.uid);
$scope.friends = $firebaseArray(friendsRef);
$scope.friendsinfo = [];
$scope.$watch('friends', function() {
var newfriends = $scope.friends;
asyncUpdateFriendsInfo(newfriends).then(function(newlist){
$scope.friendsinfo = newlist;
});
}, true);
function fetchPicture(ref){
return ref.getDownloadURL().then(function(url) {
return url;
}).catch(function(error) {
alert("error");
});
}
function fetchUserInfo(ref){
return ref.once('value', function(snapshot){
}).then(function(snapshot){
return snapshot;
});
}
function asyncUpdateFriendsInfo(newfriends){
var deferred = $q.defer();
var newfriendsinfo = [];
for(var i = 0; i < newfriends.length; i++){
var ref = firebase.database().ref('users/' + newfriends[i].$id);
var profilePicRef = firebase.storage().ref("profilepictures/" + newfriends[i].$id + "/profilepicture");
var userPromise = fetchUserInfo(ref);
var picPromise = fetchPicture(profilePicRef);
var newfriendid = newfriends[i].$id;
var newfriendagreed = newfriends[i].agreed;
userPromise.then(function(user){
picPromise.then(function(url){
newfriendsinfo.push({
id: newfriendid,
name: user.val().name,
email: user.val().email,
agreed: newfriendagreed,
profilepicture: url
});
}).then(function(){
if (newfriendsinfo.length == newfriends.length){
deferred.resolve(newfriendsinfo);
}
});
});
}
return deferred.promise;
}
答案 0 :(得分:1)
问题肯定在这段代码中。
userPromise.then(function(user){
picPromise.then(function(url){
您已嵌套承诺,但这并不能保证先解析userPromise
,然后再解析picPromise
。
它们是两个独立的异步调用。如果首先解析picPromise
,则永远不会调用以下代码。
newfriendsinfo.push({
id: newfriendid,
name: user.val().name,
email: user.val().email,
agreed: newfriendagreed,
profilepicture: url
});
除此之外,即使第一个userPromise
已解决,然后picPromise
,您仍会遇到问题。
您在promise中使用变量newfriendid
和newfriendagreed
,这是在循环中的promise之外创建的。这里有Closures的问题。
以下是调用asyncUpdateFriendsInfo
函数时会发生的情况。
当周期结束时,将发送所有请求(但尚未收到回复),newfriendid
和newfriendagreed
指向newfriends
的最后一条记录&#39; s $id
和agreed
。因此,在newfriendsinfo
newfriendid
中,所有newfriendid
都是相同的,并且将是userPromise.then(function(user){
picPromise.then(function(url){
newfriendsinfo.push({
id: newfriendid,
name: user.val().name,
email: user.val().email,
agreed: newfriendagreed,
profilepicture: url
});
}).then(function(){
if (newfriendsinfo.length == newfriends.length){
deferred.resolve(newfriendsinfo);
}
});
});
。
查看&#34; Asynchronous Process inside a javascript for loop&#34;
的这个问题如果您确实应该替换此代码
(function(newfriendid){
var finalUser,
finalUrl;
userPromise.then(function(user){
finalUser = user;
checkIfBothLoaded();
});
picPromise.then(function(url){
finalUrl = url;
checkIfBothLoaded();
});
function checkIfBothLoaded(){
if (finalUser && finalUrl){
newfriendsinfo.push({
id: newfriendid,
name: finalUser.val().name,
email: finalUser.val().email,
agreed: newfriendagreed,
profilepicture: finalUrl
});
}
if (newfriendsinfo.length == newfriends.length){
deferred.resolve(newfriendsinfo);
}
}
})(newfriendid, newfriendagreed);
这样的事情
{
"name": "First",
"version": "0.0.0",
"devDependencies": {
"aspnet-webpack": "^1.0.6",
"bootstrap": "^3.3.6",
"css-loader": "^0.23.1",
"expose-loader": "^0.7.1",
"extendify": "^1.0.0",
"extract-text-webpack-plugin": "^1.0.1",
"file-loader": "^0.8.5",
"jquery": "^2.2.1",
"raw-loader": "^0.5.1",
"style-loader": "^0.13.0",
"ts-loader": "^0.8.1",
"typescript": "^1.8.2",
"url-loader": "^0.5.7",
"webpack": "^1.12.14",
"webpack-hot-middleware": "^2.10.0"
},
"dependencies": {
"@angular/common": "2.0.0-rc.4",
"@angular/compiler": "2.0.0-rc.4",
"@angular/core": "2.0.0-rc.4",
"@angular/http": "2.0.0-rc.4",
"@angular/platform-browser": "2.0.0-rc.4",
"@angular/platform-browser-dynamic": "2.0.0-rc.4",
"@angular/platform-server": "2.0.0-rc.4",
"@angular/router": "3.0.0-beta.2",
"angular2-universal": "^0.104.5",
"aspnet-prerendering": "^1.0.2",
"css": "^2.2.1",
"es6-shim": "^0.35.1",
"isomorphic-fetch": "^2.2.1",
"materialize-css": "^0.97.7",
"preboot": "^2.0.10",
"rxjs": "5.0.0-beta.6",
"webpack-externals-plugin": "^1.0.0",
"zone.js": "^0.6.12"
}
}