Swift 使用带完成处理程序的函数时未初始化变量
我正在尝试使用SendBird聊天应用程序中可用的聊天频道数初始化可变频道。我在这个过程中使用了一个名为:private func loadChannels的函数,以便将通道加载到上述变量中。我不明白的是,调用函数时会加载通道,并且可以按照下面的代码显示。但是,当我想在LoadChannel之外显示相同变量通道的内容时,我得到一个空变量。有什么问题吗Swift 使用带完成处理程序的函数时未初始化变量,swift,scope,completionhandler,sendbird,Swift,Scope,Completionhandler,Sendbird,我正在尝试使用SendBird聊天应用程序中可用的聊天频道数初始化可变频道。我在这个过程中使用了一个名为:private func loadChannels的函数,以便将通道加载到上述变量中。我不明白的是,调用函数时会加载通道,并且可以按照下面的代码显示。但是,当我想在LoadChannel之外显示相同变量通道的内容时,我得到一个空变量。有什么问题吗 import UIKit import SendBirdSDK import JSQMessagesViewController class
import UIKit
import SendBirdSDK
import JSQMessagesViewController
class ViewController: UIViewController {
var messages = [JSQMessage]()
var channels = [SBDOpenChannel]()
private var refreshControl: UIRefreshControl?
private var openChannelListQuery: SBDOpenChannelListQuery?
override func viewDidLoad() {
//connecting to the application
SBDMain.initWithApplicationId("1662A8E8-F45F-454B-9E5E-02362342ECC5")
//Connecting the user
SBDMain.connect(withUserId: "tahrisqalli", completionHandler: { (user, error) in
// ...
print("connected tahrisqalli")
print ("printing channels")
self.loadChannels()
print (self.channels)
print ("printing channels")
self.loadChannels()
// Here content of channels variable is empty
print (self.channels)
})
}
private func loadChannels() {
self.openChannelListQuery = SBDOpenChannel.createOpenChannelListQuery()
self.openChannelListQuery?.limit = 20
if self.openChannelListQuery?.hasNext == false {
return
}
self.openChannelListQuery?.loadNextPage(completionHandler: { (channels, error) in
if error != nil {
print ("error")
return
}
for channel in channels! {
self.channels.append(channel)
}
// Here content of channels is full with the correct channels
print (self.channels)
})
}
您可以这样做:
import UIKit
import SendBirdSDK
import JSQMessagesViewController
class ViewController: UIViewController {
var messages = [JSQMessage]()
var channels = [SBDOpenChannel]()
private var refreshControl: UIRefreshControl?
private var openChannelListQuery: SBDOpenChannelListQuery?
override func viewDidLoad() {
//connecting to the application
SBDMain.initWithApplicationId("1662A8E8-F45F-454B-9E5E-02362342ECC5")
//Connecting the user
SBDMain.connect(withUserId: "tahrisqalli", completionHandler: { (user, error) in
// ...
print("connected tahrisqalli")
print ("printing channels")
self.loadChannels(){
print (self.channels)
}
//print ("printing channels")
//self.loadChannels()
// Here content of channels variable is empty
//print (self.channels)
})
}
private func loadChannels(callback: @escaping () -> void) {
self.openChannelListQuery = SBDOpenChannel.createOpenChannelListQuery()
self.openChannelListQuery?.limit = 20
if self.openChannelListQuery?.hasNext == false {
return
}
self.openChannelListQuery?.loadNextPage(completionHandler: { (channels, error) in
if error != nil {
print ("error")
return
}
for channel in channels! {
self.channels.append(channel)
}
// Here content of channels is full with the correct channels
// print (self.channels)
callback()
})
}
既然您正在一个完成处理程序中填充channels属性,我猜这个处理程序还没有被异步调用?当你到达指纹处。。。调用LoadChannel之后的语句。在这种情况下,我应该确切地将其调用到哪里?没有问题。删除self.loadChannels之后的打印行,因为正如dfri已经提到的那样,该方法是异步工作的,并且这个特定的打印行没有意义。如果我想在函数外部使用“channels”变量,我该如何做?将使用“channels”变量的代码也放入完成块中。