When I try to increase currentNumberAdmin I get:
当我试图增加currentNumberAdmin时，我得到:
cannot convert value of type 'UILabel!' to expected argument 'type in out String'
无法转换“UILabel”类型的值!" to expected arguments "输入out String "
class adminPanel: UIViewController {
@IBOutlet weak var currentNumberAdmin: UILabel!
@IBAction func nextCurrent(_ sender: UIButton) {
let database = FIRDatabase.database().reference()
database.child("current").observe(FIRDataEventType.value, with: { (snapshot) in
self.currentNumberAdmin.text = snapshot.value as! String
currentNumberAdmin += String(1)
})
}
}
Does anyone know how I can convert and increase currentNumberAdmin correctly?
有人知道我如何正确地转换和增加currentNumberAdmin吗?
1 个解决方案
#1
1
This is crashing because of this line: currentNumberAdmin += String(1). You're attempting to add a String value to a UILabel value, which is invalid. You're literally telling the compiler to assign currentNumberAdmin, a UILabel, to the value of the expression of adding a UILabel to a String, which the compiler doesn't know how to do, hence the exception message.
这是因为这一行:currentNumberAdmin += String(1)而导致的崩溃。您试图向UILabel值添加一个字符串值，该值无效。实际上，您是在告诉编译器将currentNumberAdmin(一个UILabel)分配给将UILabel添加到一个字符串的表达式的值，编译器不知道该如何做，因此有一个异常消息。
It's not entirely clear why you're attempt to set the label's text twice: once with snapshot.value, and then again on the next line. If what you're trying to do is set the label's text to the snapshot value + 1, do something like this:
不完全清楚为什么要设置标签的文本两次:一次是快照。值，然后在下一行。如果您要做的是将标签的文本设置为快照值+ 1，请执行以下操作:
@IBAction func nextCurrent(_ sender: UIButton) {
let database = FIRDatabase.database().reference()
database.child("current").observe(FIRDataEventType.value, with: { (snapshot) in
var strVal = Int(self.currentNumberAdmin.text)!
strVal += 1
self.currentNumberAdmin.text = String(strVal)
})
}
#1
1
This is crashing because of this line: currentNumberAdmin += String(1). You're attempting to add a String value to a UILabel value, which is invalid. You're literally telling the compiler to assign currentNumberAdmin, a UILabel, to the value of the expression of adding a UILabel to a String, which the compiler doesn't know how to do, hence the exception message.
这是因为这一行:currentNumberAdmin += String(1)而导致的崩溃。您试图向UILabel值添加一个字符串值，该值无效。实际上，您是在告诉编译器将currentNumberAdmin(一个UILabel)分配给将UILabel添加到一个字符串的表达式的值，编译器不知道该如何做，因此有一个异常消息。
It's not entirely clear why you're attempt to set the label's text twice: once with snapshot.value, and then again on the next line. If what you're trying to do is set the label's text to the snapshot value + 1, do something like this:
不完全清楚为什么要设置标签的文本两次:一次是快照。值，然后在下一行。如果您要做的是将标签的文本设置为快照值+ 1，请执行以下操作:
@IBAction func nextCurrent(_ sender: UIButton) {
let database = FIRDatabase.database().reference()
database.child("current").observe(FIRDataEventType.value, with: { (snapshot) in
var strVal = Int(self.currentNumberAdmin.text)!
strVal += 1
self.currentNumberAdmin.text = String(strVal)
})
}