Ios Firebase.QueryStart不工作(Swift)
这只是没有返回任何内容,即使有时间戳在这条消息之上的消息 代码排序不正确:Ios Firebase.QueryStart不工作(Swift),ios,swift,firebase,firebase-realtime-database,Ios,Swift,Firebase,Firebase Realtime Database,这只是没有返回任何内容,即使有时间戳在这条消息之上的消息 代码排序不正确: let messagesRef = FIRDatabase.database().reference().child("all-messages").child(messageId).queryOrdered(byChild: "timestamp").queryStarting(atValue: 1511130644) Firebase调用的完整代码: FIRDatabase.database().reference
let messagesRef = FIRDatabase.database().reference().child("all-messages").child(messageId).queryOrdered(byChild: "timestamp").queryStarting(atValue: 1511130644)
Firebase调用的完整代码:
FIRDatabase.database().reference().child("users").child(currentUserUid).child("timestampOfLastVisit").observeSingleEvent(of: .value, with: { (snapshot) in
timestamp = snapshot.value as! NSNumber
groupMessagesRef = FIRDatabase.database().reference().child("groups").child(groupId).child("messages")
groupMessagesRef.observe(.childAdded, with: { (snapshot) in
if self.sentMessage {
let messageId = snapshot.key
let messagesRef = FIRDatabase.database().reference().child("all-messages").child(messageId).queryOrdered(byChild: "timestamp").queryStarting(atValue: 1511130644)
messagesRef.observeSingleEvent(of: .value, with: { (snapshot) in ...
相关Firebase JSON假数据明显:
{
"all-messages" : {
"-KzLOuvEdLWy7vfc2XsT" : {
"fromId" : "zhBZyAVGvAMZWi4QhvKDu7qb3Qr1",
"groupId" : "-Kxk3kA9I8OEvNmFcavL",
"isStarred" : true,
"text" : "This should show",
"timestamp" : 1511130640
},
"-KzLOw5OxZ4P_I0d70gZ" : {
"fromId" : "zhBZyAVGvAMZWi4QhvKDu7qb3Qr1",
"groupId" : "-Kxk3kA9I8OEvNmFcavL",
"isStarred" : false,
"text" : "And so should this",
"timestamp" : 1511130644
},
"-KzLS4uwDtpW6wHNxrmc" : {
"fromId" : "zhBZyAVGvAMZWi4QhvKDu7qb3Qr1",
"groupId" : "-Kxk3kA9I8OEvNmFcavL",
"isStarred" : false,
"text" : "1",
"timestamp" : 1511131471
},
"-KzLS5FvASnj_ky4WQkd" : {
"fromId" : "zhBZyAVGvAMZWi4QhvKDu7qb3Qr1",
"groupId" : "-Kxk3kA9I8OEvNmFcavL",
"isStarred" : false,
"text" : "2",
"timestamp" : 1511131472
}
},
"groups" : {
"-Kxk3kA9I8OEvNmFcavL" : {
"groupCreator" : "zhBZyAVGvAMZWi4QhvKDu7qb3Qr1",
"groupDescription" : "Group",
"groupImageUrl" : "https://firebasestorage.googleapis.com/v0/b/groupchat1-a1da3.appspot.com/o/group_profile_images%2FA4DDA286-E7A3-4F96-ABF0-5717F4029C33.png?alt=media&token=6ad79728-74fd-405f-abbf-247dae4684b5",
"groupMemberOneSignalIds" : {
"5905a2f5-dfa3-46d7-964f-596bd2f2004a" : true,
"67b9cb2a-6583-45b4-9fed-93cf333e9ca4" : true,
"a1bf9ed9-0959-4c88-974b-5a829c1cdcc9" : true,
"f2fb84b9-86af-40e7-8667-989a95b2e282" : true
},
"groupMembers" : {
"3lQiuzudFGW51UwQ4Mseu8aOxyu2" : true,
"JF7SCe3VUcWJi1ujumx0VpyaG5s1" : true,
"YEbVehx0cqTvNaKrJTcs5GnRLGM2" : true,
"zhBZyAVGvAMZWi4QhvKDu7qb3Qr1" : true
},
"groupName" : "1",
"groupTags" : {
"-Kxk3kHxMuWQHEsaWN5k" : "1",
"-Kxk3kHyMB2OL5pNAfW1" : "1",
"-Kxk3kHyMB2OL5pNAfW2" : "1"
},
"messages" : {
"-KzLOuvEdLWy7vfc2XsT" : 1,
"-KzLOw5OxZ4P_I0d70gZ" : 1,
"-KzLS4uwDtpW6wHNxrmc" : 1,
"-KzLS5FvASnj_ky4WQkd" : 1
},
"starredMessages" : {
"-KzLOuvEdLWy7vfc2XsT" : 1511204335
}
},
"-Kxn_yTAZvkPls-_s8He" : {
"groupCreator" : "JF7SCe3VUcWJi1ujumx0VpyaG5s1",
"groupDescription" : "Group 3",
"groupImageUrl" : "https://firebasestorage.googleapis.com/v0/b/groupchat1-a1da3.appspot.com/o/group_profile_images%2FD2C68A8F-33DC-43C6-8C99-762315760208.png?alt=media&token=aae87339-877e-484e-a0e1-a2e13455176c",
"groupName" : "Group 3",
"groupTags" : {
"-Kxn_ygovR7mQIph3WiC" : "1",
"-Kxn_ygovR7mQIph3WiD" : "1"
}
}
},
"users" : {
"JF7SCe3VUcWJi1ujumx0VpyaG5s1" : {
"email" : "Madi@gmail.com",
"groups" : {
"-Kxk3kA9I8OEvNmFcavL" : true,
"-Kxk3n99i43MYECm1Ix8" : true,
"-KxuBPAPBIcROMEtNujW" : true,
"-KxuET1pZGg2x_aJvRkU" : true
},
"profileImageURL" : "https://firebasestorage.googleapis.com/v0/b/groupchat1-a1da3.appspot.com/o/profile_images%2F246CA55C-446D-4A24-8BE6-8B5B9C0F27AF.png?alt=media&token=47022ccd-1c92-460a-8630-e74a0d68bc4a",
"searchUsername" : "madi",
"timestampOfLastVisit" : 1511241228,
"username" : "Madi"
},
"zhBZyAVGvAMZWi4QhvKDu7qb3Qr1" : {
"email" : "Connor@gmail.com",
"groups" : {
"-Kxk3kA9I8OEvNmFcavL" : true,
"-Kxk3n99i43MYECm1Ix8" : true
},
"profileImageURL" : "https://firebasestorage.googleapis.com/v0/b/groupchat1-a1da3.appspot.com/o/profile_images%2FBDC4020E-9F54-4F80-A4DC-668804215DE3.png?alt=media&token=ec2c8875-e6e4-40d5-8c07-3d743bf4ea16",
"searchUsername" : "connor",
"timestampOfLastVisit" : 1511205356,
"username" : "Connor"
}
}
}
printsnapshot打印的内容:
Snap (-KzLOw5OxZ4P_I0d70gZ) <null>
queryStartingAtValue的第二个参数仅用于消除与第一个参数匹配的项之间的歧义。要按时间戳筛选,应调用queryOrderedByChildtimestamp:
目标是创建一个查询,该查询将返回具有特定时间戳的节点 问题是您的代码查询的级别太深。换句话说,您需要让Firebase在所有消息的子节点上迭代,直到它找到一个具有1511130644子时间戳的节点。所以它需要迭代
msg_0
msg_1
msg_2
等等
您的代码试图过于具体,您告诉它查看查询中数据的特定消息Id-这没有意义,因为如果您知道确切的路径,就不需要查询
这是一个常见的误解-请记住,查询需要先提供给父节点,然后提供给您所查询内容的子节点,因为它将在父节点下方的子节点上迭代
parent_node
child_node
child_node_of_what_you_are_querying
child_node
child_node_of_what_you_are_querying
下面是查询特定时间戳的代码-注意,不需要messageId
//self.ref is the firebase ref
let messagesRef = self.ref.child("all-messages").queryOrdered(byChild: "timestamp")
.queryStarting(atValue: 1511130644)
messagesRef.observeSingleEvent(of: .value, with: { (snapshot) in
if snapshot.hasChildren() {
print("got snap with children")
} else {
print("no snap found")
}
})
如果你已经知道具体的路径,你可以直接观察它。因此,如果要打印某条消息的时间戳
let thisMsgRef = self.ref.child("all-messages").child(messageId)
let thisTimestampRef = thisMsgRef.child("timestamp")
thisTimestampRef.observeSingleEvent(of: .value) { snapshot in
print(snap.value) //prints the timestamp
}
是的,我也试过了,只是碰巧我在粘贴第二个参数的时候尝试了。仍然不起作用。事实上,如果我使用.queryEqualtoValue:并只传入一个硬编码的值,我甚至无法让它工作。如果我在只有一个子节点的节点上进行排序,并观察到.childAdded而不是.value,我就可以让它工作。我添加了我正试图使用的完整Firebase代码,这导致了问题。这个问题有点到处都是;代码中引用的节点未显示在链接、所有消息、TimestampOfLastVisite、组等中。一般来说,最好包含Firebase结构的一个片段,如文本Firebase console->Export JSON,还包括处理这些特定节点的代码片段,就像引用的节点不存在一样,您的结果将是找不到节点。也许指出messagesRef实际引用的内容(例如printmessagesRef)会有所帮助。如果你能更新你的问题,我们可以看一看,也许能找到问题所在。您在上次查询中缺少.queryOrderedbyChild:timestamp,因此Firebase知道您在哪个节点上查询。@Jay更新了帖子。如果我删除.queryStartingatValue:,它会很好地工作,但它会加载所有消息。但是,我想包括.queryStartingatValue:因此我只加载自用户上次访问以来发送的消息。但是,这会导致快照值为null,并且它仍然查询所有消息,而不仅仅是时间戳之后的消息。谢谢你,杰伊!非常感谢。
//self.ref is the firebase ref
let messagesRef = self.ref.child("all-messages").queryOrdered(byChild: "timestamp")
.queryStarting(atValue: 1511130644)
messagesRef.observeSingleEvent(of: .value, with: { (snapshot) in
if snapshot.hasChildren() {
print("got snap with children")
} else {
print("no snap found")
}
})
let thisMsgRef = self.ref.child("all-messages").child(messageId)
let thisTimestampRef = thisMsgRef.child("timestamp")
thisTimestampRef.observeSingleEvent(of: .value) { snapshot in
print(snap.value) //prints the timestamp
}