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圣诞快乐/节日快乐!我试图从使用js/firebase的函数中获取变量,并在另一个函数中使用所述变量。问题在于b/c firebase是异步的,该变量在需要运行的功能之后加载。我的代码如下。在JS/FIREBASE中获取变量的问题异步执行
我的问题:如何在执行loadMessages()之前从initChatroom()中获取convoId?
// Global Variable
var convoId = '';
// Triggers when the auth state change for instance when the user signs-in or signs-out.
MyApp.prototype.onAuthStateChanged = function(user) {
if (user) { // User is signed in!
// We load currently existing chat messages.
this.initChatRoom();
this.loadMessages();
}
};
//Get chatroom name
MyApp.prototype.initChatRoom = function(){
var userId = this.auth.currentUser.uid;
return this.database.ref('/user_profiles/' + userId).once('value').then(function(snapshot) {
var agentAssigned = snapshot.val().agent_assigned;
//Gets Chatroom details
if (snapshot.hasChild("agent_assigned")){
userNameExtract = snapshot.val().nickname;
//First five user & first five counterparty
var receieverID = agentAssigned;
var senderId = userId;
var receiverIDFive = receieverID.substring(0,5);
var senderIdFive = senderId.substring(0,5);
if (senderIdFive > receiverIDFive){
convoId = senderIdFive + receiverIDFive;
}
else{
convoId = receiverIDFive + senderIdFive;
}
console.log("chatroom name", convoId);
}
else{ }
});
}
// Loads chat messages history and listens for upcoming ones.
MyApp.prototype.loadMessages = function() {
console.log("loadMessage", convoId); //CONVO ID is not loaded yet :(
this.messagesRef = this.database.ref('messages/' + convoId + '/');
// Make sure we remove all previous listeners.
this.messagesRef.off();
// Loads the last 12 messages and listen for new ones.
var self = this;
// Loads the last 12 messages and listen for new ones.
var setMessage = function(data) {
var dataVar = data.val();
self.displayMessage(data.key, dataVar.userName, dataVar.text, dataVar.type, dataVar.senderId);
};
this.messagesRef.limitToLast(12).on('child_added', setMessage);
this.messagesRef.limitToLast(12).on('child_changed', setMessage);
};
如果第二个函数依赖于第一个函数的执行,那么为什么不在那里调用它(例如:在数据库查询的回调函子中)? – UnholySheep
我曾试过这个,但我一直得到“未捕获(承诺)TypeError:无法读取未定义的属性'loadMessages' – gk103
在这种情况下,您可能在右大括号后面缺少'.bind(this)' (快照){// code} .bind(this)'应该可以)。或者你应该使用ES6脂肪箭头功能自动完成 – UnholySheep