预期返回"Int"的函数中缺少返回 [英] Missing return in a function expected to return 'Int'

问题描述

func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int
{
    canvasCount { (value) in
        if let res = value {
            return res
        }
    } //Missing return in a closure expected to return 'Int'
} //Missing return in a closure expected to return 'Int'

闭包中缺少返回值，期望返回'Int'

Missing return in a closure expected to return 'Int'

func canvasCount(completion:@escaping((_ va:Int?) -> Int )) {

    ref.child("Canvas").observeSingleEvent(of: .value, with: { (snapshot) in
        completion( snapshot.children.allObjects.count)
    }) { (error) in
        print(error.localizedDescription)
        completion(nil)
    }

}

我希望能够以整数形式返回 snapshot.children.allObjects.count .但是我用 canvasCount 函数遇到了这样的错误在闭包中缺少返回，期望返回'Int'".有人可以帮我吗?

Hi, I want to be able to return snapshot.children.allObjects.count as an integer. But I got this error "Missing return in a closure expected to return 'Int'" with canvasCount function. Anyone can help me please?

推荐答案

您需要完成，因为对firebase的调用是异步的

You need a completion as the call to firebase is asynchronous

func canvasCount(completion:@escaping((_ va:Int?) -> () )) { 

    ref.child("Canvas").observeSingleEvent(of: .value, with: { (snapshot) in
           completion( snapshot.children.allObjects.count)
    }) { (error) in
        print(error.localizedDescription)
           completion(nil)
    }

}

---

canvasCount { (value) in 
   if let res = value {
      print(res)
   }
}

-------------------------------------------------

-------------------------------------------------

声明实例变量

var counter = 0

内部 viewDidLoad 插入

canvasCount { (value) in
  if let res = value {
     self.counter =  res
     self.tableView.reloadData()
  }
} 

然后复制这些

func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int
{
    return counter
} 


func canvasCount(completion:@escaping((_ va:Int?) -> ())) {

    ref.child("Canvas").observeSingleEvent(of: .value, with: { (snapshot) in
        completion( snapshot.children.allObjects.count)
    }) { (error) in
        print(error.localizedDescription)
        completion(nil)
    }

}

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