ios - 完成 block Swift 后设置标签文本

Question

我想将用户名设置为标签，因为我的 block ("findObjectsInBackgroundWithBlock") 需要时间才能完成并且 label.text 设置了 nil 。

完成区 block 后如何设置标签文字？？

class test {         

var userName: String? // variable to access user name returned by block        
private func loadData() {      

getCurrentUser()         
lblUserName.text = userName       

}    

}

这是我从 Parse 获取用户数据的 block 。

private func getCurrentUser() {         

        if PFUser.currentUser() != nil { 

            currentUser = PFUser.currentUser()?.username    
            let query = PFQuery(className: "_User")    
            query.whereKey("username", equalTo: currentUser!)    
            query.findObjectsInBackgroundWithBlock { (currentUsers, error) -> Void in 
                if error == nil {     
                    for user in currentUsers! {     
                       userName = user["name"] as? String      
                    }   
                }
            }
        }
    }

Answer 1

你可以像这样使用属性观察器:

var userName: String? {
    didset {
       if let name = username {
           lblUserName.text = name
       } 
    }
}