我得到的参数标签'_ :, withBlock，withCancel :)'不匹配任何可用的重载。斯威夫特3

Question

使用斯威夫特3，我得到生成错误：

Argument labels '_:, withBlock, withCancel:)' do not match any available overloads

代码：

let ref = FIRDatabase.database().reference().child("users").child(chatPartnerId) 
    ref.observeSingleEventOfType.(.value, withBlock: { (snapshot) in 
     print(snapshot) 
    }, withCancel: nil) 

Answer 1

雨燕3.0

let ref = FIRDatabase.database().reference().child("users").child(chatPartnerId) 

ref.observeSingleEvent(of: .value, with: { (snapshot) in 
     print("Snapshot:", snapshot.value as! String) 
    }, withCancel: nil)