变量未使用功能时完成处理

我试图初始化变量channels与聊天频道，在我的SendBird聊天应用程序可用的数量越来越初始化。我为这个过程使用了一个函数：private func loadChannels()，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，并且可以按照您在下面的代码中看到的方式显示。但是，当我想显示loadChannels()之外的相同变量channels的内容时，我得到一个空变量。可能是什么问题？变量未使用功能时完成处理

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) 

     }) 
    }

来源

2017-07-24 user1680944

既然你在完成处理程序填补了'channels'财产，我的猜测是，这个处理器是尚未被调用（异步？）在调用loadChannels（）后到达'print（...）'语句时。 – dfri

在这种情况下，我应该在哪里准确地称呼它？ – user1680944

没有问题。在'self.loadChannels（）'之后删除'print'行，因为 - 正如dfri已经提到的那样 - 这个方法异步工作，这个特殊的'print'行是没有意义的。 – vadian

你可以这样说：

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() 

     }) 
    }

来源

2017-07-24 13:46:02 3stud1ant3

变量未使用功能时完成处理

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